1018 * allows modules to provide users with "read-only" access to internal
1019 * collections. Query operations on the returned collection "read through"
1020 * to the specified collection, and attempts to modify the returned
1021 * collection, whether direct or via its iterator, result in an
1022 * <tt>UnsupportedOperationException</tt>.<p>
1023 *
1024 * The returned collection does <i>not</i> pass the hashCode and equals
1025 * operations through to the backing collection, but relies on
1026 * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This
1027 * is necessary to preserve the contracts of these operations in the case
1028 * that the backing collection is a set or a list.<p>
1029 *
1030 * The returned collection will be serializable if the specified collection
1031 * is serializable.
1032 *
1033 * @param c the collection for which an unmodifiable view is to be
1034 * returned.
1035 * @return an unmodifiable view of the specified collection.
1036 */
1037 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
1038 return new UnmodifiableCollection<T>(c);
1039 }
1040
1041 /**
1042 * @serial include
1043 */
1044 static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
1045 private static final long serialVersionUID = 1820017752578914078L;
1046
1047 final Collection<? extends E> c;
1048
1049 UnmodifiableCollection(Collection<? extends E> c) {
1050 if (c==null)
1051 throw new NullPointerException();
1052 this.c = c;
1053 }
1054
1055 public int size() {return c.size();}
1056 public boolean isEmpty() {return c.isEmpty();}
1057 public boolean contains(Object o) {return c.contains(o);}
1058 public Object[] toArray() {return c.toArray();}
1092 }
1093 public void clear() {
1094 throw new UnsupportedOperationException();
1095 }
1096 }
1097
1098 /**
1099 * Returns an unmodifiable view of the specified set. This method allows
1100 * modules to provide users with "read-only" access to internal sets.
1101 * Query operations on the returned set "read through" to the specified
1102 * set, and attempts to modify the returned set, whether direct or via its
1103 * iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
1104 *
1105 * The returned set will be serializable if the specified set
1106 * is serializable.
1107 *
1108 * @param s the set for which an unmodifiable view is to be returned.
1109 * @return an unmodifiable view of the specified set.
1110 */
1111 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
1112 return new UnmodifiableSet<T>(s);
1113 }
1114
1115 /**
1116 * @serial include
1117 */
1118 static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
1119 implements Set<E>, Serializable {
1120 private static final long serialVersionUID = -9215047833775013803L;
1121
1122 UnmodifiableSet(Set<? extends E> s) {super(s);}
1123 public boolean equals(Object o) {return o == this || c.equals(o);}
1124 public int hashCode() {return c.hashCode();}
1125 }
1126
1127 /**
1128 * Returns an unmodifiable view of the specified sorted set. This method
1129 * allows modules to provide users with "read-only" access to internal
1130 * sorted sets. Query operations on the returned sorted set "read
1131 * through" to the specified sorted set. Attempts to modify the returned
1132 * sorted set, whether direct, via its iterator, or via its
1133 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
1134 * an <tt>UnsupportedOperationException</tt>.<p>
1135 *
1136 * The returned sorted set will be serializable if the specified sorted set
1137 * is serializable.
1138 *
1139 * @param s the sorted set for which an unmodifiable view is to be
1140 * returned.
1141 * @return an unmodifiable view of the specified sorted set.
1142 */
1143 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
1144 return new UnmodifiableSortedSet<T>(s);
1145 }
1146
1147 /**
1148 * @serial include
1149 */
1150 static class UnmodifiableSortedSet<E>
1151 extends UnmodifiableSet<E>
1152 implements SortedSet<E>, Serializable {
1153 private static final long serialVersionUID = -4929149591599911165L;
1154 private final SortedSet<E> ss;
1155
1156 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
1157
1158 public Comparator<? super E> comparator() {return ss.comparator();}
1159
1160 public SortedSet<E> subSet(E fromElement, E toElement) {
1161 return new UnmodifiableSortedSet<E>(ss.subSet(fromElement,toElement));
1162 }
1163 public SortedSet<E> headSet(E toElement) {
1164 return new UnmodifiableSortedSet<E>(ss.headSet(toElement));
1165 }
1166 public SortedSet<E> tailSet(E fromElement) {
1167 return new UnmodifiableSortedSet<E>(ss.tailSet(fromElement));
1168 }
1169
1170 public E first() {return ss.first();}
1171 public E last() {return ss.last();}
1172 }
1173
1174 /**
1175 * Returns an unmodifiable view of the specified list. This method allows
1176 * modules to provide users with "read-only" access to internal
1177 * lists. Query operations on the returned list "read through" to the
1178 * specified list, and attempts to modify the returned list, whether
1179 * direct or via its iterator, result in an
1180 * <tt>UnsupportedOperationException</tt>.<p>
1181 *
1182 * The returned list will be serializable if the specified list
1183 * is serializable. Similarly, the returned list will implement
1184 * {@link RandomAccess} if the specified list does.
1185 *
1186 * @param list the list for which an unmodifiable view is to be returned.
1187 * @return an unmodifiable view of the specified list.
1188 */
1189 public static <T> List<T> unmodifiableList(List<? extends T> list) {
1190 return (list instanceof RandomAccess ?
1191 new UnmodifiableRandomAccessList<T>(list) :
1192 new UnmodifiableList<T>(list));
1193 }
1194
1195 /**
1196 * @serial include
1197 */
1198 static class UnmodifiableList<E> extends UnmodifiableCollection<E>
1199 implements List<E> {
1200 private static final long serialVersionUID = -283967356065247728L;
1201 final List<? extends E> list;
1202
1203 UnmodifiableList(List<? extends E> list) {
1204 super(list);
1205 this.list = list;
1206 }
1207
1208 public boolean equals(Object o) {return o == this || list.equals(o);}
1209 public int hashCode() {return list.hashCode();}
1210
1211 public E get(int index) {return list.get(index);}
1212 public E set(int index, E element) {
1233 public boolean hasNext() {return i.hasNext();}
1234 public E next() {return i.next();}
1235 public boolean hasPrevious() {return i.hasPrevious();}
1236 public E previous() {return i.previous();}
1237 public int nextIndex() {return i.nextIndex();}
1238 public int previousIndex() {return i.previousIndex();}
1239
1240 public void remove() {
1241 throw new UnsupportedOperationException();
1242 }
1243 public void set(E e) {
1244 throw new UnsupportedOperationException();
1245 }
1246 public void add(E e) {
1247 throw new UnsupportedOperationException();
1248 }
1249 };
1250 }
1251
1252 public List<E> subList(int fromIndex, int toIndex) {
1253 return new UnmodifiableList<E>(list.subList(fromIndex, toIndex));
1254 }
1255
1256 /**
1257 * UnmodifiableRandomAccessList instances are serialized as
1258 * UnmodifiableList instances to allow them to be deserialized
1259 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
1260 * This method inverts the transformation. As a beneficial
1261 * side-effect, it also grafts the RandomAccess marker onto
1262 * UnmodifiableList instances that were serialized in pre-1.4 JREs.
1263 *
1264 * Note: Unfortunately, UnmodifiableRandomAccessList instances
1265 * serialized in 1.4.1 and deserialized in 1.4 will become
1266 * UnmodifiableList instances, as this method was missing in 1.4.
1267 */
1268 private Object readResolve() {
1269 return (list instanceof RandomAccess
1270 ? new UnmodifiableRandomAccessList<E>(list)
1271 : this);
1272 }
1273 }
1274
1275 /**
1276 * @serial include
1277 */
1278 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
1279 implements RandomAccess
1280 {
1281 UnmodifiableRandomAccessList(List<? extends E> list) {
1282 super(list);
1283 }
1284
1285 public List<E> subList(int fromIndex, int toIndex) {
1286 return new UnmodifiableRandomAccessList<E>(
1287 list.subList(fromIndex, toIndex));
1288 }
1289
1290 private static final long serialVersionUID = -2542308836966382001L;
1291
1292 /**
1293 * Allows instances to be deserialized in pre-1.4 JREs (which do
1294 * not have UnmodifiableRandomAccessList). UnmodifiableList has
1295 * a readResolve method that inverts this transformation upon
1296 * deserialization.
1297 */
1298 private Object writeReplace() {
1299 return new UnmodifiableList<E>(list);
1300 }
1301 }
1302
1303 /**
1304 * Returns an unmodifiable view of the specified map. This method
1305 * allows modules to provide users with "read-only" access to internal
1306 * maps. Query operations on the returned map "read through"
1307 * to the specified map, and attempts to modify the returned
1308 * map, whether direct or via its collection views, result in an
1309 * <tt>UnsupportedOperationException</tt>.<p>
1310 *
1311 * The returned map will be serializable if the specified map
1312 * is serializable.
1313 *
1314 * @param m the map for which an unmodifiable view is to be returned.
1315 * @return an unmodifiable view of the specified map.
1316 */
1317 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
1318 return new UnmodifiableMap<K,V>(m);
1319 }
1320
1321 /**
1322 * @serial include
1323 */
1324 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
1325 private static final long serialVersionUID = -1034234728574286014L;
1326
1327 private final Map<? extends K, ? extends V> m;
1328
1329 UnmodifiableMap(Map<? extends K, ? extends V> m) {
1330 if (m==null)
1331 throw new NullPointerException();
1332 this.m = m;
1333 }
1334
1335 public int size() {return m.size();}
1336 public boolean isEmpty() {return m.isEmpty();}
1337 public boolean containsKey(Object key) {return m.containsKey(key);}
1338 public boolean containsValue(Object val) {return m.containsValue(val);}
1346 }
1347 public void putAll(Map<? extends K, ? extends V> m) {
1348 throw new UnsupportedOperationException();
1349 }
1350 public void clear() {
1351 throw new UnsupportedOperationException();
1352 }
1353
1354 private transient Set<K> keySet = null;
1355 private transient Set<Map.Entry<K,V>> entrySet = null;
1356 private transient Collection<V> values = null;
1357
1358 public Set<K> keySet() {
1359 if (keySet==null)
1360 keySet = unmodifiableSet(m.keySet());
1361 return keySet;
1362 }
1363
1364 public Set<Map.Entry<K,V>> entrySet() {
1365 if (entrySet==null)
1366 entrySet = new UnmodifiableEntrySet<K,V>(m.entrySet());
1367 return entrySet;
1368 }
1369
1370 public Collection<V> values() {
1371 if (values==null)
1372 values = unmodifiableCollection(m.values());
1373 return values;
1374 }
1375
1376 public boolean equals(Object o) {return o == this || m.equals(o);}
1377 public int hashCode() {return m.hashCode();}
1378 public String toString() {return m.toString();}
1379
1380 /**
1381 * We need this class in addition to UnmodifiableSet as
1382 * Map.Entries themselves permit modification of the backing Map
1383 * via their setValue operation. This class is subtle: there are
1384 * many possible attacks that must be thwarted.
1385 *
1386 * @serial include
1387 */
1388 static class UnmodifiableEntrySet<K,V>
1389 extends UnmodifiableSet<Map.Entry<K,V>> {
1390 private static final long serialVersionUID = 7854390611657943733L;
1391
1392 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
1393 super((Set)s);
1394 }
1395 public Iterator<Map.Entry<K,V>> iterator() {
1396 return new Iterator<Map.Entry<K,V>>() {
1397 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
1398
1399 public boolean hasNext() {
1400 return i.hasNext();
1401 }
1402 public Map.Entry<K,V> next() {
1403 return new UnmodifiableEntry<K,V>(i.next());
1404 }
1405 public void remove() {
1406 throw new UnsupportedOperationException();
1407 }
1408 };
1409 }
1410
1411 public Object[] toArray() {
1412 Object[] a = c.toArray();
1413 for (int i=0; i<a.length; i++)
1414 a[i] = new UnmodifiableEntry<K,V>((Map.Entry<K,V>)a[i]);
1415 return a;
1416 }
1417
1418 public <T> T[] toArray(T[] a) {
1419 // We don't pass a to c.toArray, to avoid window of
1420 // vulnerability wherein an unscrupulous multithreaded client
1421 // could get his hands on raw (unwrapped) Entries from c.
1422 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
1423
1424 for (int i=0; i<arr.length; i++)
1425 arr[i] = new UnmodifiableEntry<K,V>((Map.Entry<K,V>)arr[i]);
1426
1427 if (arr.length > a.length)
1428 return (T[])arr;
1429
1430 System.arraycopy(arr, 0, a, 0, arr.length);
1431 if (a.length > arr.length)
1432 a[arr.length] = null;
1433 return a;
1434 }
1435
1436 /**
1437 * This method is overridden to protect the backing set against
1438 * an object with a nefarious equals function that senses
1439 * that the equality-candidate is Map.Entry and calls its
1440 * setValue method.
1441 */
1442 public boolean contains(Object o) {
1443 if (!(o instanceof Map.Entry))
1444 return false;
1445 return c.contains(
1446 new UnmodifiableEntry<Object,Object>((Map.Entry<?,?>) o));
1447 }
1448
1449 /**
1450 * The next two methods are overridden to protect against
1451 * an unscrupulous List whose contains(Object o) method senses
1452 * when o is a Map.Entry, and calls o.setValue.
1453 */
1454 public boolean containsAll(Collection<?> coll) {
1455 Iterator<?> it = coll.iterator();
1456 while (it.hasNext())
1457 if (!contains(it.next())) // Invokes safe contains() above
1458 return false;
1459 return true;
1460 }
1461 public boolean equals(Object o) {
1462 if (o == this)
1463 return true;
1464
1465 if (!(o instanceof Set))
1466 return false;
1500 }
1501 }
1502
1503 /**
1504 * Returns an unmodifiable view of the specified sorted map. This method
1505 * allows modules to provide users with "read-only" access to internal
1506 * sorted maps. Query operations on the returned sorted map "read through"
1507 * to the specified sorted map. Attempts to modify the returned
1508 * sorted map, whether direct, via its collection views, or via its
1509 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
1510 * an <tt>UnsupportedOperationException</tt>.<p>
1511 *
1512 * The returned sorted map will be serializable if the specified sorted map
1513 * is serializable.
1514 *
1515 * @param m the sorted map for which an unmodifiable view is to be
1516 * returned.
1517 * @return an unmodifiable view of the specified sorted map.
1518 */
1519 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
1520 return new UnmodifiableSortedMap<K,V>(m);
1521 }
1522
1523 /**
1524 * @serial include
1525 */
1526 static class UnmodifiableSortedMap<K,V>
1527 extends UnmodifiableMap<K,V>
1528 implements SortedMap<K,V>, Serializable {
1529 private static final long serialVersionUID = -8806743815996713206L;
1530
1531 private final SortedMap<K, ? extends V> sm;
1532
1533 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m;}
1534
1535 public Comparator<? super K> comparator() {return sm.comparator();}
1536
1537 public SortedMap<K,V> subMap(K fromKey, K toKey) {
1538 return new UnmodifiableSortedMap<K,V>(sm.subMap(fromKey, toKey));
1539 }
1540 public SortedMap<K,V> headMap(K toKey) {
1541 return new UnmodifiableSortedMap<K,V>(sm.headMap(toKey));
1542 }
1543 public SortedMap<K,V> tailMap(K fromKey) {
1544 return new UnmodifiableSortedMap<K,V>(sm.tailMap(fromKey));
1545 }
1546
1547 public K firstKey() {return sm.firstKey();}
1548 public K lastKey() {return sm.lastKey();}
1549 }
1550
1551
1552 // Synch Wrappers
1553
1554 /**
1555 * Returns a synchronized (thread-safe) collection backed by the specified
1556 * collection. In order to guarantee serial access, it is critical that
1557 * <strong>all</strong> access to the backing collection is accomplished
1558 * through the returned collection.<p>
1559 *
1560 * It is imperative that the user manually synchronize on the returned
1561 * collection when iterating over it:
1562 * <pre>
1563 * Collection c = Collections.synchronizedCollection(myCollection);
1564 * ...
1566 * Iterator i = c.iterator(); // Must be in the synchronized block
1567 * while (i.hasNext())
1568 * foo(i.next());
1569 * }
1570 * </pre>
1571 * Failure to follow this advice may result in non-deterministic behavior.
1572 *
1573 * <p>The returned collection does <i>not</i> pass the <tt>hashCode</tt>
1574 * and <tt>equals</tt> operations through to the backing collection, but
1575 * relies on <tt>Object</tt>'s equals and hashCode methods. This is
1576 * necessary to preserve the contracts of these operations in the case
1577 * that the backing collection is a set or a list.<p>
1578 *
1579 * The returned collection will be serializable if the specified collection
1580 * is serializable.
1581 *
1582 * @param c the collection to be "wrapped" in a synchronized collection.
1583 * @return a synchronized view of the specified collection.
1584 */
1585 public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
1586 return new SynchronizedCollection<T>(c);
1587 }
1588
1589 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
1590 return new SynchronizedCollection<T>(c, mutex);
1591 }
1592
1593 /**
1594 * @serial include
1595 */
1596 static class SynchronizedCollection<E> implements Collection<E>, Serializable {
1597 private static final long serialVersionUID = 3053995032091335093L;
1598
1599 final Collection<E> c; // Backing Collection
1600 final Object mutex; // Object on which to synchronize
1601
1602 SynchronizedCollection(Collection<E> c) {
1603 if (c==null)
1604 throw new NullPointerException();
1605 this.c = c;
1606 mutex = this;
1607 }
1608 SynchronizedCollection(Collection<E> c, Object mutex) {
1609 this.c = c;
1610 this.mutex = mutex;
1669 * It is imperative that the user manually synchronize on the returned
1670 * set when iterating over it:
1671 * <pre>
1672 * Set s = Collections.synchronizedSet(new HashSet());
1673 * ...
1674 * synchronized (s) {
1675 * Iterator i = s.iterator(); // Must be in the synchronized block
1676 * while (i.hasNext())
1677 * foo(i.next());
1678 * }
1679 * </pre>
1680 * Failure to follow this advice may result in non-deterministic behavior.
1681 *
1682 * <p>The returned set will be serializable if the specified set is
1683 * serializable.
1684 *
1685 * @param s the set to be "wrapped" in a synchronized set.
1686 * @return a synchronized view of the specified set.
1687 */
1688 public static <T> Set<T> synchronizedSet(Set<T> s) {
1689 return new SynchronizedSet<T>(s);
1690 }
1691
1692 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
1693 return new SynchronizedSet<T>(s, mutex);
1694 }
1695
1696 /**
1697 * @serial include
1698 */
1699 static class SynchronizedSet<E>
1700 extends SynchronizedCollection<E>
1701 implements Set<E> {
1702 private static final long serialVersionUID = 487447009682186044L;
1703
1704 SynchronizedSet(Set<E> s) {
1705 super(s);
1706 }
1707 SynchronizedSet(Set<E> s, Object mutex) {
1708 super(s, mutex);
1709 }
1710
1711 public boolean equals(Object o) {
1712 synchronized (mutex) {return c.equals(o);}
1713 }
1737 * or:
1738 * <pre>
1739 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
1740 * SortedSet s2 = s.headSet(foo);
1741 * ...
1742 * synchronized (s) { // Note: s, not s2!!!
1743 * Iterator i = s2.iterator(); // Must be in the synchronized block
1744 * while (i.hasNext())
1745 * foo(i.next());
1746 * }
1747 * </pre>
1748 * Failure to follow this advice may result in non-deterministic behavior.
1749 *
1750 * <p>The returned sorted set will be serializable if the specified
1751 * sorted set is serializable.
1752 *
1753 * @param s the sorted set to be "wrapped" in a synchronized sorted set.
1754 * @return a synchronized view of the specified sorted set.
1755 */
1756 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
1757 return new SynchronizedSortedSet<T>(s);
1758 }
1759
1760 /**
1761 * @serial include
1762 */
1763 static class SynchronizedSortedSet<E>
1764 extends SynchronizedSet<E>
1765 implements SortedSet<E>
1766 {
1767 private static final long serialVersionUID = 8695801310862127406L;
1768
1769 private final SortedSet<E> ss;
1770
1771 SynchronizedSortedSet(SortedSet<E> s) {
1772 super(s);
1773 ss = s;
1774 }
1775 SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
1776 super(s, mutex);
1777 ss = s;
1778 }
1779
1780 public Comparator<? super E> comparator() {
1781 synchronized (mutex) {return ss.comparator();}
1782 }
1783
1784 public SortedSet<E> subSet(E fromElement, E toElement) {
1785 synchronized (mutex) {
1786 return new SynchronizedSortedSet<E>(
1787 ss.subSet(fromElement, toElement), mutex);
1788 }
1789 }
1790 public SortedSet<E> headSet(E toElement) {
1791 synchronized (mutex) {
1792 return new SynchronizedSortedSet<E>(ss.headSet(toElement), mutex);
1793 }
1794 }
1795 public SortedSet<E> tailSet(E fromElement) {
1796 synchronized (mutex) {
1797 return new SynchronizedSortedSet<E>(ss.tailSet(fromElement),mutex);
1798 }
1799 }
1800
1801 public E first() {
1802 synchronized (mutex) {return ss.first();}
1803 }
1804 public E last() {
1805 synchronized (mutex) {return ss.last();}
1806 }
1807 }
1808
1809 /**
1810 * Returns a synchronized (thread-safe) list backed by the specified
1811 * list. In order to guarantee serial access, it is critical that
1812 * <strong>all</strong> access to the backing list is accomplished
1813 * through the returned list.<p>
1814 *
1815 * It is imperative that the user manually synchronize on the returned
1816 * list when iterating over it:
1817 * <pre>
1818 * List list = Collections.synchronizedList(new ArrayList());
1819 * ...
1820 * synchronized (list) {
1821 * Iterator i = list.iterator(); // Must be in synchronized block
1822 * while (i.hasNext())
1823 * foo(i.next());
1824 * }
1825 * </pre>
1826 * Failure to follow this advice may result in non-deterministic behavior.
1827 *
1828 * <p>The returned list will be serializable if the specified list is
1829 * serializable.
1830 *
1831 * @param list the list to be "wrapped" in a synchronized list.
1832 * @return a synchronized view of the specified list.
1833 */
1834 public static <T> List<T> synchronizedList(List<T> list) {
1835 return (list instanceof RandomAccess ?
1836 new SynchronizedRandomAccessList<T>(list) :
1837 new SynchronizedList<T>(list));
1838 }
1839
1840 static <T> List<T> synchronizedList(List<T> list, Object mutex) {
1841 return (list instanceof RandomAccess ?
1842 new SynchronizedRandomAccessList<T>(list, mutex) :
1843 new SynchronizedList<T>(list, mutex));
1844 }
1845
1846 /**
1847 * @serial include
1848 */
1849 static class SynchronizedList<E>
1850 extends SynchronizedCollection<E>
1851 implements List<E> {
1852 private static final long serialVersionUID = -7754090372962971524L;
1853
1854 final List<E> list;
1855
1856 SynchronizedList(List<E> list) {
1857 super(list);
1858 this.list = list;
1859 }
1860 SynchronizedList(List<E> list, Object mutex) {
1861 super(list, mutex);
1862 this.list = list;
1863 }
1886 synchronized (mutex) {return list.indexOf(o);}
1887 }
1888 public int lastIndexOf(Object o) {
1889 synchronized (mutex) {return list.lastIndexOf(o);}
1890 }
1891
1892 public boolean addAll(int index, Collection<? extends E> c) {
1893 synchronized (mutex) {return list.addAll(index, c);}
1894 }
1895
1896 public ListIterator<E> listIterator() {
1897 return list.listIterator(); // Must be manually synched by user
1898 }
1899
1900 public ListIterator<E> listIterator(int index) {
1901 return list.listIterator(index); // Must be manually synched by user
1902 }
1903
1904 public List<E> subList(int fromIndex, int toIndex) {
1905 synchronized (mutex) {
1906 return new SynchronizedList<E>(list.subList(fromIndex, toIndex),
1907 mutex);
1908 }
1909 }
1910
1911 /**
1912 * SynchronizedRandomAccessList instances are serialized as
1913 * SynchronizedList instances to allow them to be deserialized
1914 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
1915 * This method inverts the transformation. As a beneficial
1916 * side-effect, it also grafts the RandomAccess marker onto
1917 * SynchronizedList instances that were serialized in pre-1.4 JREs.
1918 *
1919 * Note: Unfortunately, SynchronizedRandomAccessList instances
1920 * serialized in 1.4.1 and deserialized in 1.4 will become
1921 * SynchronizedList instances, as this method was missing in 1.4.
1922 */
1923 private Object readResolve() {
1924 return (list instanceof RandomAccess
1925 ? new SynchronizedRandomAccessList<E>(list)
1926 : this);
1927 }
1928 }
1929
1930 /**
1931 * @serial include
1932 */
1933 static class SynchronizedRandomAccessList<E>
1934 extends SynchronizedList<E>
1935 implements RandomAccess {
1936
1937 SynchronizedRandomAccessList(List<E> list) {
1938 super(list);
1939 }
1940
1941 SynchronizedRandomAccessList(List<E> list, Object mutex) {
1942 super(list, mutex);
1943 }
1944
1945 public List<E> subList(int fromIndex, int toIndex) {
1946 synchronized (mutex) {
1947 return new SynchronizedRandomAccessList<E>(
1948 list.subList(fromIndex, toIndex), mutex);
1949 }
1950 }
1951
1952 private static final long serialVersionUID = 1530674583602358482L;
1953
1954 /**
1955 * Allows instances to be deserialized in pre-1.4 JREs (which do
1956 * not have SynchronizedRandomAccessList). SynchronizedList has
1957 * a readResolve method that inverts this transformation upon
1958 * deserialization.
1959 */
1960 private Object writeReplace() {
1961 return new SynchronizedList<E>(list);
1962 }
1963 }
1964
1965 /**
1966 * Returns a synchronized (thread-safe) map backed by the specified
1967 * map. In order to guarantee serial access, it is critical that
1968 * <strong>all</strong> access to the backing map is accomplished
1969 * through the returned map.<p>
1970 *
1971 * It is imperative that the user manually synchronize on the returned
1972 * map when iterating over any of its collection views:
1973 * <pre>
1974 * Map m = Collections.synchronizedMap(new HashMap());
1975 * ...
1976 * Set s = m.keySet(); // Needn't be in synchronized block
1977 * ...
1978 * synchronized (m) { // Synchronizing on m, not s!
1979 * Iterator i = s.iterator(); // Must be in synchronized block
1980 * while (i.hasNext())
1981 * foo(i.next());
1982 * }
1983 * </pre>
1984 * Failure to follow this advice may result in non-deterministic behavior.
1985 *
1986 * <p>The returned map will be serializable if the specified map is
1987 * serializable.
1988 *
1989 * @param m the map to be "wrapped" in a synchronized map.
1990 * @return a synchronized view of the specified map.
1991 */
1992 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
1993 return new SynchronizedMap<K,V>(m);
1994 }
1995
1996 /**
1997 * @serial include
1998 */
1999 private static class SynchronizedMap<K,V>
2000 implements Map<K,V>, Serializable {
2001 private static final long serialVersionUID = 1978198479659022715L;
2002
2003 private final Map<K,V> m; // Backing Map
2004 final Object mutex; // Object on which to synchronize
2005
2006 SynchronizedMap(Map<K,V> m) {
2007 if (m==null)
2008 throw new NullPointerException();
2009 this.m = m;
2010 mutex = this;
2011 }
2012
2013 SynchronizedMap(Map<K,V> m, Object mutex) {
2034 public V put(K key, V value) {
2035 synchronized (mutex) {return m.put(key, value);}
2036 }
2037 public V remove(Object key) {
2038 synchronized (mutex) {return m.remove(key);}
2039 }
2040 public void putAll(Map<? extends K, ? extends V> map) {
2041 synchronized (mutex) {m.putAll(map);}
2042 }
2043 public void clear() {
2044 synchronized (mutex) {m.clear();}
2045 }
2046
2047 private transient Set<K> keySet = null;
2048 private transient Set<Map.Entry<K,V>> entrySet = null;
2049 private transient Collection<V> values = null;
2050
2051 public Set<K> keySet() {
2052 synchronized (mutex) {
2053 if (keySet==null)
2054 keySet = new SynchronizedSet<K>(m.keySet(), mutex);
2055 return keySet;
2056 }
2057 }
2058
2059 public Set<Map.Entry<K,V>> entrySet() {
2060 synchronized (mutex) {
2061 if (entrySet==null)
2062 entrySet = new SynchronizedSet<Map.Entry<K,V>>(m.entrySet(), mutex);
2063 return entrySet;
2064 }
2065 }
2066
2067 public Collection<V> values() {
2068 synchronized (mutex) {
2069 if (values==null)
2070 values = new SynchronizedCollection<V>(m.values(), mutex);
2071 return values;
2072 }
2073 }
2074
2075 public boolean equals(Object o) {
2076 synchronized (mutex) {return m.equals(o);}
2077 }
2078 public int hashCode() {
2079 synchronized (mutex) {return m.hashCode();}
2080 }
2081 public String toString() {
2082 synchronized (mutex) {return m.toString();}
2083 }
2084 private void writeObject(ObjectOutputStream s) throws IOException {
2085 synchronized (mutex) {s.defaultWriteObject();}
2086 }
2087 }
2088
2089 /**
2090 * Returns a synchronized (thread-safe) sorted map backed by the specified
2112 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2113 * SortedMap m2 = m.subMap(foo, bar);
2114 * ...
2115 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2116 * ...
2117 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2118 * Iterator i = s.iterator(); // Must be in synchronized block
2119 * while (i.hasNext())
2120 * foo(i.next());
2121 * }
2122 * </pre>
2123 * Failure to follow this advice may result in non-deterministic behavior.
2124 *
2125 * <p>The returned sorted map will be serializable if the specified
2126 * sorted map is serializable.
2127 *
2128 * @param m the sorted map to be "wrapped" in a synchronized sorted map.
2129 * @return a synchronized view of the specified sorted map.
2130 */
2131 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
2132 return new SynchronizedSortedMap<K,V>(m);
2133 }
2134
2135
2136 /**
2137 * @serial include
2138 */
2139 static class SynchronizedSortedMap<K,V>
2140 extends SynchronizedMap<K,V>
2141 implements SortedMap<K,V>
2142 {
2143 private static final long serialVersionUID = -8798146769416483793L;
2144
2145 private final SortedMap<K,V> sm;
2146
2147 SynchronizedSortedMap(SortedMap<K,V> m) {
2148 super(m);
2149 sm = m;
2150 }
2151 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
2152 super(m, mutex);
2153 sm = m;
2154 }
2155
2156 public Comparator<? super K> comparator() {
2157 synchronized (mutex) {return sm.comparator();}
2158 }
2159
2160 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2161 synchronized (mutex) {
2162 return new SynchronizedSortedMap<K,V>(
2163 sm.subMap(fromKey, toKey), mutex);
2164 }
2165 }
2166 public SortedMap<K,V> headMap(K toKey) {
2167 synchronized (mutex) {
2168 return new SynchronizedSortedMap<K,V>(sm.headMap(toKey), mutex);
2169 }
2170 }
2171 public SortedMap<K,V> tailMap(K fromKey) {
2172 synchronized (mutex) {
2173 return new SynchronizedSortedMap<K,V>(sm.tailMap(fromKey),mutex);
2174 }
2175 }
2176
2177 public K firstKey() {
2178 synchronized (mutex) {return sm.firstKey();}
2179 }
2180 public K lastKey() {
2181 synchronized (mutex) {return sm.lastKey();}
2182 }
2183 }
2184
2185 // Dynamically typesafe collection wrappers
2186
2187 /**
2188 * Returns a dynamically typesafe view of the specified collection.
2189 * Any attempt to insert an element of the wrong type will result in an
2190 * immediate {@link ClassCastException}. Assuming a collection
2191 * contains no incorrectly typed elements prior to the time a
2192 * dynamically typesafe view is generated, and that all subsequent
2193 * access to the collection takes place through the view, it is
2229 * operations through to the backing collection, but relies on
2230 * {@code Object}'s {@code equals} and {@code hashCode} methods. This
2231 * is necessary to preserve the contracts of these operations in the case
2232 * that the backing collection is a set or a list.
2233 *
2234 * <p>The returned collection will be serializable if the specified
2235 * collection is serializable.
2236 *
2237 * <p>Since {@code null} is considered to be a value of any reference
2238 * type, the returned collection permits insertion of null elements
2239 * whenever the backing collection does.
2240 *
2241 * @param c the collection for which a dynamically typesafe view is to be
2242 * returned
2243 * @param type the type of element that {@code c} is permitted to hold
2244 * @return a dynamically typesafe view of the specified collection
2245 * @since 1.5
2246 */
2247 public static <E> Collection<E> checkedCollection(Collection<E> c,
2248 Class<E> type) {
2249 return new CheckedCollection<E>(c, type);
2250 }
2251
2252 @SuppressWarnings("unchecked")
2253 static <T> T[] zeroLengthArray(Class<T> type) {
2254 return (T[]) Array.newInstance(type, 0);
2255 }
2256
2257 /**
2258 * @serial include
2259 */
2260 static class CheckedCollection<E> implements Collection<E>, Serializable {
2261 private static final long serialVersionUID = 1578914078182001775L;
2262
2263 final Collection<E> c;
2264 final Class<E> type;
2265
2266 void typeCheck(Object o) {
2267 if (o != null && !type.isInstance(o))
2268 throw new ClassCastException(badElementMsg(o));
2269 }
2361 * set cannot contain an incorrectly typed element.
2362 *
2363 * <p>A discussion of the use of dynamically typesafe views may be
2364 * found in the documentation for the {@link #checkedCollection
2365 * checkedCollection} method.
2366 *
2367 * <p>The returned set will be serializable if the specified set is
2368 * serializable.
2369 *
2370 * <p>Since {@code null} is considered to be a value of any reference
2371 * type, the returned set permits insertion of null elements whenever
2372 * the backing set does.
2373 *
2374 * @param s the set for which a dynamically typesafe view is to be
2375 * returned
2376 * @param type the type of element that {@code s} is permitted to hold
2377 * @return a dynamically typesafe view of the specified set
2378 * @since 1.5
2379 */
2380 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
2381 return new CheckedSet<E>(s, type);
2382 }
2383
2384 /**
2385 * @serial include
2386 */
2387 static class CheckedSet<E> extends CheckedCollection<E>
2388 implements Set<E>, Serializable
2389 {
2390 private static final long serialVersionUID = 4694047833775013803L;
2391
2392 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
2393
2394 public boolean equals(Object o) { return o == this || c.equals(o); }
2395 public int hashCode() { return c.hashCode(); }
2396 }
2397
2398 /**
2399 * Returns a dynamically typesafe view of the specified sorted set.
2400 * Any attempt to insert an element of the wrong type will result in an
2401 * immediate {@link ClassCastException}. Assuming a sorted set
2407 *
2408 * <p>A discussion of the use of dynamically typesafe views may be
2409 * found in the documentation for the {@link #checkedCollection
2410 * checkedCollection} method.
2411 *
2412 * <p>The returned sorted set will be serializable if the specified sorted
2413 * set is serializable.
2414 *
2415 * <p>Since {@code null} is considered to be a value of any reference
2416 * type, the returned sorted set permits insertion of null elements
2417 * whenever the backing sorted set does.
2418 *
2419 * @param s the sorted set for which a dynamically typesafe view is to be
2420 * returned
2421 * @param type the type of element that {@code s} is permitted to hold
2422 * @return a dynamically typesafe view of the specified sorted set
2423 * @since 1.5
2424 */
2425 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
2426 Class<E> type) {
2427 return new CheckedSortedSet<E>(s, type);
2428 }
2429
2430 /**
2431 * @serial include
2432 */
2433 static class CheckedSortedSet<E> extends CheckedSet<E>
2434 implements SortedSet<E>, Serializable
2435 {
2436 private static final long serialVersionUID = 1599911165492914959L;
2437 private final SortedSet<E> ss;
2438
2439 CheckedSortedSet(SortedSet<E> s, Class<E> type) {
2440 super(s, type);
2441 ss = s;
2442 }
2443
2444 public Comparator<? super E> comparator() { return ss.comparator(); }
2445 public E first() { return ss.first(); }
2446 public E last() { return ss.last(); }
2447
2467 *
2468 * <p>A discussion of the use of dynamically typesafe views may be
2469 * found in the documentation for the {@link #checkedCollection
2470 * checkedCollection} method.
2471 *
2472 * <p>The returned list will be serializable if the specified list
2473 * is serializable.
2474 *
2475 * <p>Since {@code null} is considered to be a value of any reference
2476 * type, the returned list permits insertion of null elements whenever
2477 * the backing list does.
2478 *
2479 * @param list the list for which a dynamically typesafe view is to be
2480 * returned
2481 * @param type the type of element that {@code list} is permitted to hold
2482 * @return a dynamically typesafe view of the specified list
2483 * @since 1.5
2484 */
2485 public static <E> List<E> checkedList(List<E> list, Class<E> type) {
2486 return (list instanceof RandomAccess ?
2487 new CheckedRandomAccessList<E>(list, type) :
2488 new CheckedList<E>(list, type));
2489 }
2490
2491 /**
2492 * @serial include
2493 */
2494 static class CheckedList<E>
2495 extends CheckedCollection<E>
2496 implements List<E>
2497 {
2498 private static final long serialVersionUID = 65247728283967356L;
2499 final List<E> list;
2500
2501 CheckedList(List<E> list, Class<E> type) {
2502 super(list, type);
2503 this.list = list;
2504 }
2505
2506 public boolean equals(Object o) { return o == this || list.equals(o); }
2507 public int hashCode() { return list.hashCode(); }
2508 public E get(int index) { return list.get(index); }
2533 public E next() { return i.next(); }
2534 public boolean hasPrevious() { return i.hasPrevious(); }
2535 public E previous() { return i.previous(); }
2536 public int nextIndex() { return i.nextIndex(); }
2537 public int previousIndex() { return i.previousIndex(); }
2538 public void remove() { i.remove(); }
2539
2540 public void set(E e) {
2541 typeCheck(e);
2542 i.set(e);
2543 }
2544
2545 public void add(E e) {
2546 typeCheck(e);
2547 i.add(e);
2548 }
2549 };
2550 }
2551
2552 public List<E> subList(int fromIndex, int toIndex) {
2553 return new CheckedList<E>(list.subList(fromIndex, toIndex), type);
2554 }
2555 }
2556
2557 /**
2558 * @serial include
2559 */
2560 static class CheckedRandomAccessList<E> extends CheckedList<E>
2561 implements RandomAccess
2562 {
2563 private static final long serialVersionUID = 1638200125423088369L;
2564
2565 CheckedRandomAccessList(List<E> list, Class<E> type) {
2566 super(list, type);
2567 }
2568
2569 public List<E> subList(int fromIndex, int toIndex) {
2570 return new CheckedRandomAccessList<E>(
2571 list.subList(fromIndex, toIndex), type);
2572 }
2573 }
2574
2575 /**
2576 * Returns a dynamically typesafe view of the specified map.
2577 * Any attempt to insert a mapping whose key or value have the wrong
2578 * type will result in an immediate {@link ClassCastException}.
2579 * Similarly, any attempt to modify the value currently associated with
2580 * a key will result in an immediate {@link ClassCastException},
2581 * whether the modification is attempted directly through the map
2582 * itself, or through a {@link Map.Entry} instance obtained from the
2583 * map's {@link Map#entrySet() entry set} view.
2584 *
2585 * <p>Assuming a map contains no incorrectly typed keys or values
2586 * prior to the time a dynamically typesafe view is generated, and
2587 * that all subsequent access to the map takes place through the view
2588 * (or one of its collection views), it is <i>guaranteed</i> that the
2589 * map cannot contain an incorrectly typed key or value.
2590 *
2592 * found in the documentation for the {@link #checkedCollection
2593 * checkedCollection} method.
2594 *
2595 * <p>The returned map will be serializable if the specified map is
2596 * serializable.
2597 *
2598 * <p>Since {@code null} is considered to be a value of any reference
2599 * type, the returned map permits insertion of null keys or values
2600 * whenever the backing map does.
2601 *
2602 * @param m the map for which a dynamically typesafe view is to be
2603 * returned
2604 * @param keyType the type of key that {@code m} is permitted to hold
2605 * @param valueType the type of value that {@code m} is permitted to hold
2606 * @return a dynamically typesafe view of the specified map
2607 * @since 1.5
2608 */
2609 public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
2610 Class<K> keyType,
2611 Class<V> valueType) {
2612 return new CheckedMap<K,V>(m, keyType, valueType);
2613 }
2614
2615
2616 /**
2617 * @serial include
2618 */
2619 private static class CheckedMap<K,V>
2620 implements Map<K,V>, Serializable
2621 {
2622 private static final long serialVersionUID = 5742860141034234728L;
2623
2624 private final Map<K, V> m;
2625 final Class<K> keyType;
2626 final Class<V> valueType;
2627
2628 private void typeCheck(Object key, Object value) {
2629 if (key != null && !keyType.isInstance(key))
2630 throw new ClassCastException(badKeyMsg(key));
2631
2632 if (value != null && !valueType.isInstance(value))
2661 public Set<K> keySet() { return m.keySet(); }
2662 public Collection<V> values() { return m.values(); }
2663 public boolean equals(Object o) { return o == this || m.equals(o); }
2664 public int hashCode() { return m.hashCode(); }
2665 public String toString() { return m.toString(); }
2666
2667 public V put(K key, V value) {
2668 typeCheck(key, value);
2669 return m.put(key, value);
2670 }
2671
2672 @SuppressWarnings("unchecked")
2673 public void putAll(Map<? extends K, ? extends V> t) {
2674 // Satisfy the following goals:
2675 // - good diagnostics in case of type mismatch
2676 // - all-or-nothing semantics
2677 // - protection from malicious t
2678 // - correct behavior if t is a concurrent map
2679 Object[] entries = t.entrySet().toArray();
2680 List<Map.Entry<K,V>> checked =
2681 new ArrayList<Map.Entry<K,V>>(entries.length);
2682 for (Object o : entries) {
2683 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
2684 Object k = e.getKey();
2685 Object v = e.getValue();
2686 typeCheck(k, v);
2687 checked.add(
2688 new AbstractMap.SimpleImmutableEntry<K,V>((K) k, (V) v));
2689 }
2690 for (Map.Entry<K,V> e : checked)
2691 m.put(e.getKey(), e.getValue());
2692 }
2693
2694 private transient Set<Map.Entry<K,V>> entrySet = null;
2695
2696 public Set<Map.Entry<K,V>> entrySet() {
2697 if (entrySet==null)
2698 entrySet = new CheckedEntrySet<K,V>(m.entrySet(), valueType);
2699 return entrySet;
2700 }
2701
2702 /**
2703 * We need this class in addition to CheckedSet as Map.Entry permits
2704 * modification of the backing Map via the setValue operation. This
2705 * class is subtle: there are many possible attacks that must be
2706 * thwarted.
2707 *
2708 * @serial exclude
2709 */
2710 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
2711 private final Set<Map.Entry<K,V>> s;
2712 private final Class<V> valueType;
2713
2714 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
2715 this.s = s;
2716 this.valueType = valueType;
2717 }
2718
2793 return s.contains(
2794 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
2795 }
2796
2797 /**
2798 * The bulk collection methods are overridden to protect
2799 * against an unscrupulous collection whose contains(Object o)
2800 * method senses when o is a Map.Entry, and calls o.setValue.
2801 */
2802 public boolean containsAll(Collection<?> c) {
2803 for (Object o : c)
2804 if (!contains(o)) // Invokes safe contains() above
2805 return false;
2806 return true;
2807 }
2808
2809 public boolean remove(Object o) {
2810 if (!(o instanceof Map.Entry))
2811 return false;
2812 return s.remove(new AbstractMap.SimpleImmutableEntry
2813 <Object, Object>((Map.Entry<?,?>)o));
2814 }
2815
2816 public boolean removeAll(Collection<?> c) {
2817 return batchRemove(c, false);
2818 }
2819 public boolean retainAll(Collection<?> c) {
2820 return batchRemove(c, true);
2821 }
2822 private boolean batchRemove(Collection<?> c, boolean complement) {
2823 boolean modified = false;
2824 Iterator<Map.Entry<K,V>> it = iterator();
2825 while (it.hasNext()) {
2826 if (c.contains(it.next()) != complement) {
2827 it.remove();
2828 modified = true;
2829 }
2830 }
2831 return modified;
2832 }
2833
2834 public boolean equals(Object o) {
2835 if (o == this)
2836 return true;
2837 if (!(o instanceof Set))
2838 return false;
2839 Set<?> that = (Set<?>) o;
2840 return that.size() == s.size()
2841 && containsAll(that); // Invokes safe containsAll() above
2842 }
2843
2844 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
2845 Class<T> valueType) {
2846 return new CheckedEntry<K,V,T>(e, valueType);
2847 }
2848
2849 /**
2850 * This "wrapper class" serves two purposes: it prevents
2851 * the client from modifying the backing Map, by short-circuiting
2852 * the setValue method, and it protects the backing Map against
2853 * an ill-behaved Map.Entry that attempts to modify another
2854 * Map.Entry when asked to perform an equality check.
2855 */
2856 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
2857 private final Map.Entry<K, V> e;
2858 private final Class<T> valueType;
2859
2860 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
2861 this.e = e;
2862 this.valueType = valueType;
2863 }
2864
2865 public K getKey() { return e.getKey(); }
2866 public V getValue() { return e.getValue(); }
2867 public int hashCode() { return e.hashCode(); }
2868 public String toString() { return e.toString(); }
2869
2870 public V setValue(V value) {
2871 if (value != null && !valueType.isInstance(value))
2872 throw new ClassCastException(badValueMsg(value));
2873 return e.setValue(value);
2874 }
2875
2876 private String badValueMsg(Object value) {
2877 return "Attempt to insert " + value.getClass() +
2878 " value into map with value type " + valueType;
2879 }
2880
2881 public boolean equals(Object o) {
2882 if (o == this)
2883 return true;
2884 if (!(o instanceof Map.Entry))
2885 return false;
2886 return e.equals(new AbstractMap.SimpleImmutableEntry
2887 <Object, Object>((Map.Entry<?,?>)o));
2888 }
2889 }
2890 }
2891 }
2892
2893 /**
2894 * Returns a dynamically typesafe view of the specified sorted map.
2895 * Any attempt to insert a mapping whose key or value have the wrong
2896 * type will result in an immediate {@link ClassCastException}.
2897 * Similarly, any attempt to modify the value currently associated with
2898 * a key will result in an immediate {@link ClassCastException},
2899 * whether the modification is attempted directly through the map
2900 * itself, or through a {@link Map.Entry} instance obtained from the
2901 * map's {@link Map#entrySet() entry set} view.
2902 *
2903 * <p>Assuming a map contains no incorrectly typed keys or values
2904 * prior to the time a dynamically typesafe view is generated, and
2905 * that all subsequent access to the map takes place through the view
2906 * (or one of its collection views), it is <i>guaranteed</i> that the
2907 * map cannot contain an incorrectly typed key or value.
2910 * found in the documentation for the {@link #checkedCollection
2911 * checkedCollection} method.
2912 *
2913 * <p>The returned map will be serializable if the specified map is
2914 * serializable.
2915 *
2916 * <p>Since {@code null} is considered to be a value of any reference
2917 * type, the returned map permits insertion of null keys or values
2918 * whenever the backing map does.
2919 *
2920 * @param m the map for which a dynamically typesafe view is to be
2921 * returned
2922 * @param keyType the type of key that {@code m} is permitted to hold
2923 * @param valueType the type of value that {@code m} is permitted to hold
2924 * @return a dynamically typesafe view of the specified map
2925 * @since 1.5
2926 */
2927 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
2928 Class<K> keyType,
2929 Class<V> valueType) {
2930 return new CheckedSortedMap<K,V>(m, keyType, valueType);
2931 }
2932
2933 /**
2934 * @serial include
2935 */
2936 static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
2937 implements SortedMap<K,V>, Serializable
2938 {
2939 private static final long serialVersionUID = 1599671320688067438L;
2940
2941 private final SortedMap<K, V> sm;
2942
2943 CheckedSortedMap(SortedMap<K, V> m,
2944 Class<K> keyType, Class<V> valueType) {
2945 super(m, keyType, valueType);
2946 sm = m;
2947 }
2948
2949 public Comparator<? super K> comparator() { return sm.comparator(); }
2950 public K firstKey() { return sm.firstKey(); }
2976 * NoSuchElementException}.
2977 *
2978 * <li>{@link Iterator#remove remove} always throws {@link
2979 * IllegalStateException}.
2980 *
2981 * </ul>
2982 *
2983 * <p>Implementations of this method are permitted, but not
2984 * required, to return the same object from multiple invocations.
2985 *
2986 * @return an empty iterator
2987 * @since 1.7
2988 */
2989 @SuppressWarnings("unchecked")
2990 public static <T> Iterator<T> emptyIterator() {
2991 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
2992 }
2993
2994 private static class EmptyIterator<E> implements Iterator<E> {
2995 static final EmptyIterator<Object> EMPTY_ITERATOR
2996 = new EmptyIterator<Object>();
2997
2998 public boolean hasNext() { return false; }
2999 public E next() { throw new NoSuchElementException(); }
3000 public void remove() { throw new IllegalStateException(); }
3001 }
3002
3003 /**
3004 * Returns a list iterator that has no elements. More precisely,
3005 *
3006 * <ul compact>
3007 *
3008 * <li>{@link Iterator#hasNext hasNext} and {@link
3009 * ListIterator#hasPrevious hasPrevious} always return {@code
3010 * false}.
3011 *
3012 * <li>{@link Iterator#next next} and {@link ListIterator#previous
3013 * previous} always throw {@link NoSuchElementException}.
3014 *
3015 * <li>{@link Iterator#remove remove} and {@link ListIterator#set
3016 * set} always throw {@link IllegalStateException}.
3025 * returns {@code -1}.
3026 *
3027 * </ul>
3028 *
3029 * <p>Implementations of this method are permitted, but not
3030 * required, to return the same object from multiple invocations.
3031 *
3032 * @return an empty list iterator
3033 * @since 1.7
3034 */
3035 @SuppressWarnings("unchecked")
3036 public static <T> ListIterator<T> emptyListIterator() {
3037 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
3038 }
3039
3040 private static class EmptyListIterator<E>
3041 extends EmptyIterator<E>
3042 implements ListIterator<E>
3043 {
3044 static final EmptyListIterator<Object> EMPTY_ITERATOR
3045 = new EmptyListIterator<Object>();
3046
3047 public boolean hasPrevious() { return false; }
3048 public E previous() { throw new NoSuchElementException(); }
3049 public int nextIndex() { return 0; }
3050 public int previousIndex() { return -1; }
3051 public void set(E e) { throw new IllegalStateException(); }
3052 public void add(E e) { throw new UnsupportedOperationException(); }
3053 }
3054
3055 /**
3056 * Returns an enumeration that has no elements. More precisely,
3057 *
3058 * <ul compact>
3059 *
3060 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always
3061 * returns {@code false}.
3062 *
3063 * <li> {@link Enumeration#nextElement nextElement} always throws
3064 * {@link NoSuchElementException}.
3065 *
3066 * </ul>
3067 *
3068 * <p>Implementations of this method are permitted, but not
3069 * required, to return the same object from multiple invocations.
3070 *
3071 * @return an empty enumeration
3072 * @since 1.7
3073 */
3074 @SuppressWarnings("unchecked")
3075 public static <T> Enumeration<T> emptyEnumeration() {
3076 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
3077 }
3078
3079 private static class EmptyEnumeration<E> implements Enumeration<E> {
3080 static final EmptyEnumeration<Object> EMPTY_ENUMERATION
3081 = new EmptyEnumeration<Object>();
3082
3083 public boolean hasMoreElements() { return false; }
3084 public E nextElement() { throw new NoSuchElementException(); }
3085 }
3086
3087 /**
3088 * The empty set (immutable). This set is serializable.
3089 *
3090 * @see #emptySet()
3091 */
3092 @SuppressWarnings("unchecked")
3093 public static final Set EMPTY_SET = new EmptySet<Object>();
3094
3095 /**
3096 * Returns the empty set (immutable). This set is serializable.
3097 * Unlike the like-named field, this method is parameterized.
3098 *
3099 * <p>This example illustrates the type-safe way to obtain an empty set:
3100 * <pre>
3101 * Set<String> s = Collections.emptySet();
3102 * </pre>
3103 * Implementation note: Implementations of this method need not
3104 * create a separate <tt>Set</tt> object for each call. Using this
3105 * method is likely to have comparable cost to using the like-named
3106 * field. (Unlike this method, the field does not provide type safety.)
3107 *
3108 * @see #EMPTY_SET
3109 * @since 1.5
3110 */
3111 @SuppressWarnings("unchecked")
3112 public static final <T> Set<T> emptySet() {
3113 return (Set<T>) EMPTY_SET;
3133 public Object[] toArray() { return new Object[0]; }
3134
3135 public <T> T[] toArray(T[] a) {
3136 if (a.length > 0)
3137 a[0] = null;
3138 return a;
3139 }
3140
3141 // Preserves singleton property
3142 private Object readResolve() {
3143 return EMPTY_SET;
3144 }
3145 }
3146
3147 /**
3148 * The empty list (immutable). This list is serializable.
3149 *
3150 * @see #emptyList()
3151 */
3152 @SuppressWarnings("unchecked")
3153 public static final List EMPTY_LIST = new EmptyList<Object>();
3154
3155 /**
3156 * Returns the empty list (immutable). This list is serializable.
3157 *
3158 * <p>This example illustrates the type-safe way to obtain an empty list:
3159 * <pre>
3160 * List<String> s = Collections.emptyList();
3161 * </pre>
3162 * Implementation note: Implementations of this method need not
3163 * create a separate <tt>List</tt> object for each call. Using this
3164 * method is likely to have comparable cost to using the like-named
3165 * field. (Unlike this method, the field does not provide type safety.)
3166 *
3167 * @see #EMPTY_LIST
3168 * @since 1.5
3169 */
3170 @SuppressWarnings("unchecked")
3171 public static final <T> List<T> emptyList() {
3172 return (List<T>) EMPTY_LIST;
3173 }
3207
3208 public boolean equals(Object o) {
3209 return (o instanceof List) && ((List<?>)o).isEmpty();
3210 }
3211
3212 public int hashCode() { return 1; }
3213
3214 // Preserves singleton property
3215 private Object readResolve() {
3216 return EMPTY_LIST;
3217 }
3218 }
3219
3220 /**
3221 * The empty map (immutable). This map is serializable.
3222 *
3223 * @see #emptyMap()
3224 * @since 1.3
3225 */
3226 @SuppressWarnings("unchecked")
3227 public static final Map EMPTY_MAP = new EmptyMap<Object,Object>();
3228
3229 /**
3230 * Returns the empty map (immutable). This map is serializable.
3231 *
3232 * <p>This example illustrates the type-safe way to obtain an empty set:
3233 * <pre>
3234 * Map<String, Date> s = Collections.emptyMap();
3235 * </pre>
3236 * Implementation note: Implementations of this method need not
3237 * create a separate <tt>Map</tt> object for each call. Using this
3238 * method is likely to have comparable cost to using the like-named
3239 * field. (Unlike this method, the field does not provide type safety.)
3240 *
3241 * @see #EMPTY_MAP
3242 * @since 1.5
3243 */
3244 @SuppressWarnings("unchecked")
3245 public static final <K,V> Map<K,V> emptyMap() {
3246 return (Map<K,V>) EMPTY_MAP;
3247 }
3269 }
3270
3271 public int hashCode() {return 0;}
3272
3273 // Preserves singleton property
3274 private Object readResolve() {
3275 return EMPTY_MAP;
3276 }
3277 }
3278
3279 // Singleton collections
3280
3281 /**
3282 * Returns an immutable set containing only the specified object.
3283 * The returned set is serializable.
3284 *
3285 * @param o the sole object to be stored in the returned set.
3286 * @return an immutable set containing only the specified object.
3287 */
3288 public static <T> Set<T> singleton(T o) {
3289 return new SingletonSet<T>(o);
3290 }
3291
3292 static <E> Iterator<E> singletonIterator(final E e) {
3293 return new Iterator<E>() {
3294 private boolean hasNext = true;
3295 public boolean hasNext() {
3296 return hasNext;
3297 }
3298 public E next() {
3299 if (hasNext) {
3300 hasNext = false;
3301 return e;
3302 }
3303 throw new NoSuchElementException();
3304 }
3305 public void remove() {
3306 throw new UnsupportedOperationException();
3307 }
3308 };
3309 }
3322 SingletonSet(E e) {element = e;}
3323
3324 public Iterator<E> iterator() {
3325 return singletonIterator(element);
3326 }
3327
3328 public int size() {return 1;}
3329
3330 public boolean contains(Object o) {return eq(o, element);}
3331 }
3332
3333 /**
3334 * Returns an immutable list containing only the specified object.
3335 * The returned list is serializable.
3336 *
3337 * @param o the sole object to be stored in the returned list.
3338 * @return an immutable list containing only the specified object.
3339 * @since 1.3
3340 */
3341 public static <T> List<T> singletonList(T o) {
3342 return new SingletonList<T>(o);
3343 }
3344
3345 /**
3346 * @serial include
3347 */
3348 private static class SingletonList<E>
3349 extends AbstractList<E>
3350 implements RandomAccess, Serializable {
3351
3352 private static final long serialVersionUID = 3093736618740652951L;
3353
3354 private final E element;
3355
3356 SingletonList(E obj) {element = obj;}
3357
3358 public Iterator<E> iterator() {
3359 return singletonIterator(element);
3360 }
3361
3362 public int size() {return 1;}
3364 public boolean contains(Object obj) {return eq(obj, element);}
3365
3366 public E get(int index) {
3367 if (index != 0)
3368 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
3369 return element;
3370 }
3371 }
3372
3373 /**
3374 * Returns an immutable map, mapping only the specified key to the
3375 * specified value. The returned map is serializable.
3376 *
3377 * @param key the sole key to be stored in the returned map.
3378 * @param value the value to which the returned map maps <tt>key</tt>.
3379 * @return an immutable map containing only the specified key-value
3380 * mapping.
3381 * @since 1.3
3382 */
3383 public static <K,V> Map<K,V> singletonMap(K key, V value) {
3384 return new SingletonMap<K,V>(key, value);
3385 }
3386
3387 /**
3388 * @serial include
3389 */
3390 private static class SingletonMap<K,V>
3391 extends AbstractMap<K,V>
3392 implements Serializable {
3393 private static final long serialVersionUID = -6979724477215052911L;
3394
3395 private final K k;
3396 private final V v;
3397
3398 SingletonMap(K key, V value) {
3399 k = key;
3400 v = value;
3401 }
3402
3403 public int size() {return 1;}
3404
3406
3407 public boolean containsKey(Object key) {return eq(key, k);}
3408
3409 public boolean containsValue(Object value) {return eq(value, v);}
3410
3411 public V get(Object key) {return (eq(key, k) ? v : null);}
3412
3413 private transient Set<K> keySet = null;
3414 private transient Set<Map.Entry<K,V>> entrySet = null;
3415 private transient Collection<V> values = null;
3416
3417 public Set<K> keySet() {
3418 if (keySet==null)
3419 keySet = singleton(k);
3420 return keySet;
3421 }
3422
3423 public Set<Map.Entry<K,V>> entrySet() {
3424 if (entrySet==null)
3425 entrySet = Collections.<Map.Entry<K,V>>singleton(
3426 new SimpleImmutableEntry<K,V>(k, v));
3427 return entrySet;
3428 }
3429
3430 public Collection<V> values() {
3431 if (values==null)
3432 values = singleton(v);
3433 return values;
3434 }
3435
3436 }
3437
3438 // Miscellaneous
3439
3440 /**
3441 * Returns an immutable list consisting of <tt>n</tt> copies of the
3442 * specified object. The newly allocated data object is tiny (it contains
3443 * a single reference to the data object). This method is useful in
3444 * combination with the <tt>List.addAll</tt> method to grow lists.
3445 * The returned list is serializable.
3446 *
3447 * @param n the number of elements in the returned list.
3448 * @param o the element to appear repeatedly in the returned list.
3449 * @return an immutable list consisting of <tt>n</tt> copies of the
3450 * specified object.
3451 * @throws IllegalArgumentException if {@code n < 0}
3452 * @see List#addAll(Collection)
3453 * @see List#addAll(int, Collection)
3454 */
3455 public static <T> List<T> nCopies(int n, T o) {
3456 if (n < 0)
3457 throw new IllegalArgumentException("List length = " + n);
3458 return new CopiesList<T>(n, o);
3459 }
3460
3461 /**
3462 * @serial include
3463 */
3464 private static class CopiesList<E>
3465 extends AbstractList<E>
3466 implements RandomAccess, Serializable
3467 {
3468 private static final long serialVersionUID = 2739099268398711800L;
3469
3470 final int n;
3471 final E element;
3472
3473 CopiesList(int n, E e) {
3474 assert n >= 0;
3475 this.n = n;
3476 element = e;
3477 }
3478
3512 a = (T[])java.lang.reflect.Array
3513 .newInstance(a.getClass().getComponentType(), n);
3514 if (element != null)
3515 Arrays.fill(a, 0, n, element);
3516 } else {
3517 Arrays.fill(a, 0, n, element);
3518 if (a.length > n)
3519 a[n] = null;
3520 }
3521 return a;
3522 }
3523
3524 public List<E> subList(int fromIndex, int toIndex) {
3525 if (fromIndex < 0)
3526 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
3527 if (toIndex > n)
3528 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
3529 if (fromIndex > toIndex)
3530 throw new IllegalArgumentException("fromIndex(" + fromIndex +
3531 ") > toIndex(" + toIndex + ")");
3532 return new CopiesList<E>(toIndex - fromIndex, element);
3533 }
3534 }
3535
3536 /**
3537 * Returns a comparator that imposes the reverse of the <i>natural
3538 * ordering</i> on a collection of objects that implement the
3539 * <tt>Comparable</tt> interface. (The natural ordering is the ordering
3540 * imposed by the objects' own <tt>compareTo</tt> method.) This enables a
3541 * simple idiom for sorting (or maintaining) collections (or arrays) of
3542 * objects that implement the <tt>Comparable</tt> interface in
3543 * reverse-natural-order. For example, suppose a is an array of
3544 * strings. Then: <pre>
3545 * Arrays.sort(a, Collections.reverseOrder());
3546 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p>
3547 *
3548 * The returned comparator is serializable.
3549 *
3550 * @return a comparator that imposes the reverse of the <i>natural
3551 * ordering</i> on a collection of objects that implement
3552 * the <tt>Comparable</tt> interface.
3578 * Returns a comparator that imposes the reverse ordering of the specified
3579 * comparator. If the specified comparator is null, this method is
3580 * equivalent to {@link #reverseOrder()} (in other words, it returns a
3581 * comparator that imposes the reverse of the <i>natural ordering</i> on a
3582 * collection of objects that implement the Comparable interface).
3583 *
3584 * <p>The returned comparator is serializable (assuming the specified
3585 * comparator is also serializable or null).
3586 *
3587 * @return a comparator that imposes the reverse ordering of the
3588 * specified comparator
3589 * @since 1.5
3590 */
3591 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
3592 if (cmp == null)
3593 return reverseOrder();
3594
3595 if (cmp instanceof ReverseComparator2)
3596 return ((ReverseComparator2<T>)cmp).cmp;
3597
3598 return new ReverseComparator2<T>(cmp);
3599 }
3600
3601 /**
3602 * @serial include
3603 */
3604 private static class ReverseComparator2<T> implements Comparator<T>,
3605 Serializable
3606 {
3607 private static final long serialVersionUID = 4374092139857L;
3608
3609 /**
3610 * The comparator specified in the static factory. This will never
3611 * be null, as the static factory returns a ReverseComparator
3612 * instance if its argument is null.
3613 *
3614 * @serial
3615 */
3616 final Comparator<T> cmp;
3617
3618 ReverseComparator2(Comparator<T> cmp) {
3657 }
3658 };
3659 }
3660
3661 /**
3662 * Returns an array list containing the elements returned by the
3663 * specified enumeration in the order they are returned by the
3664 * enumeration. This method provides interoperability between
3665 * legacy APIs that return enumerations and new APIs that require
3666 * collections.
3667 *
3668 * @param e enumeration providing elements for the returned
3669 * array list
3670 * @return an array list containing the elements returned
3671 * by the specified enumeration.
3672 * @since 1.4
3673 * @see Enumeration
3674 * @see ArrayList
3675 */
3676 public static <T> ArrayList<T> list(Enumeration<T> e) {
3677 ArrayList<T> l = new ArrayList<T>();
3678 while (e.hasMoreElements())
3679 l.add(e.nextElement());
3680 return l;
3681 }
3682
3683 /**
3684 * Returns true if the specified arguments are equal, or both null.
3685 */
3686 static boolean eq(Object o1, Object o2) {
3687 return o1==null ? o2==null : o1.equals(o2);
3688 }
3689
3690 /**
3691 * Returns the number of elements in the specified collection equal to the
3692 * specified object. More formally, returns the number of elements
3693 * <tt>e</tt> in the collection such that
3694 * <tt>(o == null ? e == null : o.equals(e))</tt>.
3695 *
3696 * @param c the collection in which to determine the frequency
3697 * of <tt>o</tt>
3802 * exactly one method invocation on the backing map or its <tt>keySet</tt>
3803 * view, with one exception. The <tt>addAll</tt> method is implemented
3804 * as a sequence of <tt>put</tt> invocations on the backing map.
3805 *
3806 * <p>The specified map must be empty at the time this method is invoked,
3807 * and should not be accessed directly after this method returns. These
3808 * conditions are ensured if the map is created empty, passed directly
3809 * to this method, and no reference to the map is retained, as illustrated
3810 * in the following code fragment:
3811 * <pre>
3812 * Set<Object> weakHashSet = Collections.newSetFromMap(
3813 * new WeakHashMap<Object, Boolean>());
3814 * </pre>
3815 *
3816 * @param map the backing map
3817 * @return the set backed by the map
3818 * @throws IllegalArgumentException if <tt>map</tt> is not empty
3819 * @since 1.6
3820 */
3821 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
3822 return new SetFromMap<E>(map);
3823 }
3824
3825 /**
3826 * @serial include
3827 */
3828 private static class SetFromMap<E> extends AbstractSet<E>
3829 implements Set<E>, Serializable
3830 {
3831 private final Map<E, Boolean> m; // The backing map
3832 private transient Set<E> s; // Its keySet
3833
3834 SetFromMap(Map<E, Boolean> map) {
3835 if (!map.isEmpty())
3836 throw new IllegalArgumentException("Map is non-empty");
3837 m = map;
3838 s = map.keySet();
3839 }
3840
3841 public void clear() { m.clear(); }
3842 public int size() { return m.size(); }
3866 }
3867
3868 /**
3869 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo)
3870 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>,
3871 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This
3872 * view can be useful when you would like to use a method
3873 * requiring a <tt>Queue</tt> but you need Lifo ordering.
3874 *
3875 * <p>Each method invocation on the queue returned by this method
3876 * results in exactly one method invocation on the backing deque, with
3877 * one exception. The {@link Queue#addAll addAll} method is
3878 * implemented as a sequence of {@link Deque#addFirst addFirst}
3879 * invocations on the backing deque.
3880 *
3881 * @param deque the deque
3882 * @return the queue
3883 * @since 1.6
3884 */
3885 public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
3886 return new AsLIFOQueue<T>(deque);
3887 }
3888
3889 /**
3890 * @serial include
3891 */
3892 static class AsLIFOQueue<E> extends AbstractQueue<E>
3893 implements Queue<E>, Serializable {
3894 private static final long serialVersionUID = 1802017725587941708L;
3895 private final Deque<E> q;
3896 AsLIFOQueue(Deque<E> q) { this.q = q; }
3897 public boolean add(E e) { q.addFirst(e); return true; }
3898 public boolean offer(E e) { return q.offerFirst(e); }
3899 public E poll() { return q.pollFirst(); }
3900 public E remove() { return q.removeFirst(); }
3901 public E peek() { return q.peekFirst(); }
3902 public E element() { return q.getFirst(); }
3903 public void clear() { q.clear(); }
3904 public int size() { return q.size(); }
3905 public boolean isEmpty() { return q.isEmpty(); }
3906 public boolean contains(Object o) { return q.contains(o); }
|
1018 * allows modules to provide users with "read-only" access to internal
1019 * collections. Query operations on the returned collection "read through"
1020 * to the specified collection, and attempts to modify the returned
1021 * collection, whether direct or via its iterator, result in an
1022 * <tt>UnsupportedOperationException</tt>.<p>
1023 *
1024 * The returned collection does <i>not</i> pass the hashCode and equals
1025 * operations through to the backing collection, but relies on
1026 * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This
1027 * is necessary to preserve the contracts of these operations in the case
1028 * that the backing collection is a set or a list.<p>
1029 *
1030 * The returned collection will be serializable if the specified collection
1031 * is serializable.
1032 *
1033 * @param c the collection for which an unmodifiable view is to be
1034 * returned.
1035 * @return an unmodifiable view of the specified collection.
1036 */
1037 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
1038 return new UnmodifiableCollection<>(c);
1039 }
1040
1041 /**
1042 * @serial include
1043 */
1044 static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
1045 private static final long serialVersionUID = 1820017752578914078L;
1046
1047 final Collection<? extends E> c;
1048
1049 UnmodifiableCollection(Collection<? extends E> c) {
1050 if (c==null)
1051 throw new NullPointerException();
1052 this.c = c;
1053 }
1054
1055 public int size() {return c.size();}
1056 public boolean isEmpty() {return c.isEmpty();}
1057 public boolean contains(Object o) {return c.contains(o);}
1058 public Object[] toArray() {return c.toArray();}
1092 }
1093 public void clear() {
1094 throw new UnsupportedOperationException();
1095 }
1096 }
1097
1098 /**
1099 * Returns an unmodifiable view of the specified set. This method allows
1100 * modules to provide users with "read-only" access to internal sets.
1101 * Query operations on the returned set "read through" to the specified
1102 * set, and attempts to modify the returned set, whether direct or via its
1103 * iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
1104 *
1105 * The returned set will be serializable if the specified set
1106 * is serializable.
1107 *
1108 * @param s the set for which an unmodifiable view is to be returned.
1109 * @return an unmodifiable view of the specified set.
1110 */
1111 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
1112 return new UnmodifiableSet<>(s);
1113 }
1114
1115 /**
1116 * @serial include
1117 */
1118 static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
1119 implements Set<E>, Serializable {
1120 private static final long serialVersionUID = -9215047833775013803L;
1121
1122 UnmodifiableSet(Set<? extends E> s) {super(s);}
1123 public boolean equals(Object o) {return o == this || c.equals(o);}
1124 public int hashCode() {return c.hashCode();}
1125 }
1126
1127 /**
1128 * Returns an unmodifiable view of the specified sorted set. This method
1129 * allows modules to provide users with "read-only" access to internal
1130 * sorted sets. Query operations on the returned sorted set "read
1131 * through" to the specified sorted set. Attempts to modify the returned
1132 * sorted set, whether direct, via its iterator, or via its
1133 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
1134 * an <tt>UnsupportedOperationException</tt>.<p>
1135 *
1136 * The returned sorted set will be serializable if the specified sorted set
1137 * is serializable.
1138 *
1139 * @param s the sorted set for which an unmodifiable view is to be
1140 * returned.
1141 * @return an unmodifiable view of the specified sorted set.
1142 */
1143 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
1144 return new UnmodifiableSortedSet<>(s);
1145 }
1146
1147 /**
1148 * @serial include
1149 */
1150 static class UnmodifiableSortedSet<E>
1151 extends UnmodifiableSet<E>
1152 implements SortedSet<E>, Serializable {
1153 private static final long serialVersionUID = -4929149591599911165L;
1154 private final SortedSet<E> ss;
1155
1156 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
1157
1158 public Comparator<? super E> comparator() {return ss.comparator();}
1159
1160 public SortedSet<E> subSet(E fromElement, E toElement) {
1161 return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
1162 }
1163 public SortedSet<E> headSet(E toElement) {
1164 return new UnmodifiableSortedSet<>(ss.headSet(toElement));
1165 }
1166 public SortedSet<E> tailSet(E fromElement) {
1167 return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
1168 }
1169
1170 public E first() {return ss.first();}
1171 public E last() {return ss.last();}
1172 }
1173
1174 /**
1175 * Returns an unmodifiable view of the specified list. This method allows
1176 * modules to provide users with "read-only" access to internal
1177 * lists. Query operations on the returned list "read through" to the
1178 * specified list, and attempts to modify the returned list, whether
1179 * direct or via its iterator, result in an
1180 * <tt>UnsupportedOperationException</tt>.<p>
1181 *
1182 * The returned list will be serializable if the specified list
1183 * is serializable. Similarly, the returned list will implement
1184 * {@link RandomAccess} if the specified list does.
1185 *
1186 * @param list the list for which an unmodifiable view is to be returned.
1187 * @return an unmodifiable view of the specified list.
1188 */
1189 public static <T> List<T> unmodifiableList(List<? extends T> list) {
1190 return (list instanceof RandomAccess ?
1191 new UnmodifiableRandomAccessList<>(list) :
1192 new UnmodifiableList<>(list));
1193 }
1194
1195 /**
1196 * @serial include
1197 */
1198 static class UnmodifiableList<E> extends UnmodifiableCollection<E>
1199 implements List<E> {
1200 private static final long serialVersionUID = -283967356065247728L;
1201 final List<? extends E> list;
1202
1203 UnmodifiableList(List<? extends E> list) {
1204 super(list);
1205 this.list = list;
1206 }
1207
1208 public boolean equals(Object o) {return o == this || list.equals(o);}
1209 public int hashCode() {return list.hashCode();}
1210
1211 public E get(int index) {return list.get(index);}
1212 public E set(int index, E element) {
1233 public boolean hasNext() {return i.hasNext();}
1234 public E next() {return i.next();}
1235 public boolean hasPrevious() {return i.hasPrevious();}
1236 public E previous() {return i.previous();}
1237 public int nextIndex() {return i.nextIndex();}
1238 public int previousIndex() {return i.previousIndex();}
1239
1240 public void remove() {
1241 throw new UnsupportedOperationException();
1242 }
1243 public void set(E e) {
1244 throw new UnsupportedOperationException();
1245 }
1246 public void add(E e) {
1247 throw new UnsupportedOperationException();
1248 }
1249 };
1250 }
1251
1252 public List<E> subList(int fromIndex, int toIndex) {
1253 return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
1254 }
1255
1256 /**
1257 * UnmodifiableRandomAccessList instances are serialized as
1258 * UnmodifiableList instances to allow them to be deserialized
1259 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
1260 * This method inverts the transformation. As a beneficial
1261 * side-effect, it also grafts the RandomAccess marker onto
1262 * UnmodifiableList instances that were serialized in pre-1.4 JREs.
1263 *
1264 * Note: Unfortunately, UnmodifiableRandomAccessList instances
1265 * serialized in 1.4.1 and deserialized in 1.4 will become
1266 * UnmodifiableList instances, as this method was missing in 1.4.
1267 */
1268 private Object readResolve() {
1269 return (list instanceof RandomAccess
1270 ? new UnmodifiableRandomAccessList<>(list)
1271 : this);
1272 }
1273 }
1274
1275 /**
1276 * @serial include
1277 */
1278 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
1279 implements RandomAccess
1280 {
1281 UnmodifiableRandomAccessList(List<? extends E> list) {
1282 super(list);
1283 }
1284
1285 public List<E> subList(int fromIndex, int toIndex) {
1286 return new UnmodifiableRandomAccessList<>(
1287 list.subList(fromIndex, toIndex));
1288 }
1289
1290 private static final long serialVersionUID = -2542308836966382001L;
1291
1292 /**
1293 * Allows instances to be deserialized in pre-1.4 JREs (which do
1294 * not have UnmodifiableRandomAccessList). UnmodifiableList has
1295 * a readResolve method that inverts this transformation upon
1296 * deserialization.
1297 */
1298 private Object writeReplace() {
1299 return new UnmodifiableList<>(list);
1300 }
1301 }
1302
1303 /**
1304 * Returns an unmodifiable view of the specified map. This method
1305 * allows modules to provide users with "read-only" access to internal
1306 * maps. Query operations on the returned map "read through"
1307 * to the specified map, and attempts to modify the returned
1308 * map, whether direct or via its collection views, result in an
1309 * <tt>UnsupportedOperationException</tt>.<p>
1310 *
1311 * The returned map will be serializable if the specified map
1312 * is serializable.
1313 *
1314 * @param m the map for which an unmodifiable view is to be returned.
1315 * @return an unmodifiable view of the specified map.
1316 */
1317 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
1318 return new UnmodifiableMap<>(m);
1319 }
1320
1321 /**
1322 * @serial include
1323 */
1324 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
1325 private static final long serialVersionUID = -1034234728574286014L;
1326
1327 private final Map<? extends K, ? extends V> m;
1328
1329 UnmodifiableMap(Map<? extends K, ? extends V> m) {
1330 if (m==null)
1331 throw new NullPointerException();
1332 this.m = m;
1333 }
1334
1335 public int size() {return m.size();}
1336 public boolean isEmpty() {return m.isEmpty();}
1337 public boolean containsKey(Object key) {return m.containsKey(key);}
1338 public boolean containsValue(Object val) {return m.containsValue(val);}
1346 }
1347 public void putAll(Map<? extends K, ? extends V> m) {
1348 throw new UnsupportedOperationException();
1349 }
1350 public void clear() {
1351 throw new UnsupportedOperationException();
1352 }
1353
1354 private transient Set<K> keySet = null;
1355 private transient Set<Map.Entry<K,V>> entrySet = null;
1356 private transient Collection<V> values = null;
1357
1358 public Set<K> keySet() {
1359 if (keySet==null)
1360 keySet = unmodifiableSet(m.keySet());
1361 return keySet;
1362 }
1363
1364 public Set<Map.Entry<K,V>> entrySet() {
1365 if (entrySet==null)
1366 entrySet = new UnmodifiableEntrySet<>(m.entrySet());
1367 return entrySet;
1368 }
1369
1370 public Collection<V> values() {
1371 if (values==null)
1372 values = unmodifiableCollection(m.values());
1373 return values;
1374 }
1375
1376 public boolean equals(Object o) {return o == this || m.equals(o);}
1377 public int hashCode() {return m.hashCode();}
1378 public String toString() {return m.toString();}
1379
1380 /**
1381 * We need this class in addition to UnmodifiableSet as
1382 * Map.Entries themselves permit modification of the backing Map
1383 * via their setValue operation. This class is subtle: there are
1384 * many possible attacks that must be thwarted.
1385 *
1386 * @serial include
1387 */
1388 static class UnmodifiableEntrySet<K,V>
1389 extends UnmodifiableSet<Map.Entry<K,V>> {
1390 private static final long serialVersionUID = 7854390611657943733L;
1391
1392 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
1393 super((Set)s);
1394 }
1395 public Iterator<Map.Entry<K,V>> iterator() {
1396 return new Iterator<Map.Entry<K,V>>() {
1397 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
1398
1399 public boolean hasNext() {
1400 return i.hasNext();
1401 }
1402 public Map.Entry<K,V> next() {
1403 return new UnmodifiableEntry<>(i.next());
1404 }
1405 public void remove() {
1406 throw new UnsupportedOperationException();
1407 }
1408 };
1409 }
1410
1411 public Object[] toArray() {
1412 Object[] a = c.toArray();
1413 for (int i=0; i<a.length; i++)
1414 a[i] = new UnmodifiableEntry<>((Map.Entry<K,V>)a[i]);
1415 return a;
1416 }
1417
1418 public <T> T[] toArray(T[] a) {
1419 // We don't pass a to c.toArray, to avoid window of
1420 // vulnerability wherein an unscrupulous multithreaded client
1421 // could get his hands on raw (unwrapped) Entries from c.
1422 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
1423
1424 for (int i=0; i<arr.length; i++)
1425 arr[i] = new UnmodifiableEntry<>((Map.Entry<K,V>)arr[i]);
1426
1427 if (arr.length > a.length)
1428 return (T[])arr;
1429
1430 System.arraycopy(arr, 0, a, 0, arr.length);
1431 if (a.length > arr.length)
1432 a[arr.length] = null;
1433 return a;
1434 }
1435
1436 /**
1437 * This method is overridden to protect the backing set against
1438 * an object with a nefarious equals function that senses
1439 * that the equality-candidate is Map.Entry and calls its
1440 * setValue method.
1441 */
1442 public boolean contains(Object o) {
1443 if (!(o instanceof Map.Entry))
1444 return false;
1445 return c.contains(
1446 new UnmodifiableEntry<>((Map.Entry<?,?>) o));
1447 }
1448
1449 /**
1450 * The next two methods are overridden to protect against
1451 * an unscrupulous List whose contains(Object o) method senses
1452 * when o is a Map.Entry, and calls o.setValue.
1453 */
1454 public boolean containsAll(Collection<?> coll) {
1455 Iterator<?> it = coll.iterator();
1456 while (it.hasNext())
1457 if (!contains(it.next())) // Invokes safe contains() above
1458 return false;
1459 return true;
1460 }
1461 public boolean equals(Object o) {
1462 if (o == this)
1463 return true;
1464
1465 if (!(o instanceof Set))
1466 return false;
1500 }
1501 }
1502
1503 /**
1504 * Returns an unmodifiable view of the specified sorted map. This method
1505 * allows modules to provide users with "read-only" access to internal
1506 * sorted maps. Query operations on the returned sorted map "read through"
1507 * to the specified sorted map. Attempts to modify the returned
1508 * sorted map, whether direct, via its collection views, or via its
1509 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
1510 * an <tt>UnsupportedOperationException</tt>.<p>
1511 *
1512 * The returned sorted map will be serializable if the specified sorted map
1513 * is serializable.
1514 *
1515 * @param m the sorted map for which an unmodifiable view is to be
1516 * returned.
1517 * @return an unmodifiable view of the specified sorted map.
1518 */
1519 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
1520 return new UnmodifiableSortedMap<>(m);
1521 }
1522
1523 /**
1524 * @serial include
1525 */
1526 static class UnmodifiableSortedMap<K,V>
1527 extends UnmodifiableMap<K,V>
1528 implements SortedMap<K,V>, Serializable {
1529 private static final long serialVersionUID = -8806743815996713206L;
1530
1531 private final SortedMap<K, ? extends V> sm;
1532
1533 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m;}
1534
1535 public Comparator<? super K> comparator() {return sm.comparator();}
1536
1537 public SortedMap<K,V> subMap(K fromKey, K toKey) {
1538 return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey));
1539 }
1540 public SortedMap<K,V> headMap(K toKey) {
1541 return new UnmodifiableSortedMap<>(sm.headMap(toKey));
1542 }
1543 public SortedMap<K,V> tailMap(K fromKey) {
1544 return new UnmodifiableSortedMap<>(sm.tailMap(fromKey));
1545 }
1546
1547 public K firstKey() {return sm.firstKey();}
1548 public K lastKey() {return sm.lastKey();}
1549 }
1550
1551
1552 // Synch Wrappers
1553
1554 /**
1555 * Returns a synchronized (thread-safe) collection backed by the specified
1556 * collection. In order to guarantee serial access, it is critical that
1557 * <strong>all</strong> access to the backing collection is accomplished
1558 * through the returned collection.<p>
1559 *
1560 * It is imperative that the user manually synchronize on the returned
1561 * collection when iterating over it:
1562 * <pre>
1563 * Collection c = Collections.synchronizedCollection(myCollection);
1564 * ...
1566 * Iterator i = c.iterator(); // Must be in the synchronized block
1567 * while (i.hasNext())
1568 * foo(i.next());
1569 * }
1570 * </pre>
1571 * Failure to follow this advice may result in non-deterministic behavior.
1572 *
1573 * <p>The returned collection does <i>not</i> pass the <tt>hashCode</tt>
1574 * and <tt>equals</tt> operations through to the backing collection, but
1575 * relies on <tt>Object</tt>'s equals and hashCode methods. This is
1576 * necessary to preserve the contracts of these operations in the case
1577 * that the backing collection is a set or a list.<p>
1578 *
1579 * The returned collection will be serializable if the specified collection
1580 * is serializable.
1581 *
1582 * @param c the collection to be "wrapped" in a synchronized collection.
1583 * @return a synchronized view of the specified collection.
1584 */
1585 public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
1586 return new SynchronizedCollection<>(c);
1587 }
1588
1589 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
1590 return new SynchronizedCollection<>(c, mutex);
1591 }
1592
1593 /**
1594 * @serial include
1595 */
1596 static class SynchronizedCollection<E> implements Collection<E>, Serializable {
1597 private static final long serialVersionUID = 3053995032091335093L;
1598
1599 final Collection<E> c; // Backing Collection
1600 final Object mutex; // Object on which to synchronize
1601
1602 SynchronizedCollection(Collection<E> c) {
1603 if (c==null)
1604 throw new NullPointerException();
1605 this.c = c;
1606 mutex = this;
1607 }
1608 SynchronizedCollection(Collection<E> c, Object mutex) {
1609 this.c = c;
1610 this.mutex = mutex;
1669 * It is imperative that the user manually synchronize on the returned
1670 * set when iterating over it:
1671 * <pre>
1672 * Set s = Collections.synchronizedSet(new HashSet());
1673 * ...
1674 * synchronized (s) {
1675 * Iterator i = s.iterator(); // Must be in the synchronized block
1676 * while (i.hasNext())
1677 * foo(i.next());
1678 * }
1679 * </pre>
1680 * Failure to follow this advice may result in non-deterministic behavior.
1681 *
1682 * <p>The returned set will be serializable if the specified set is
1683 * serializable.
1684 *
1685 * @param s the set to be "wrapped" in a synchronized set.
1686 * @return a synchronized view of the specified set.
1687 */
1688 public static <T> Set<T> synchronizedSet(Set<T> s) {
1689 return new SynchronizedSet<>(s);
1690 }
1691
1692 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
1693 return new SynchronizedSet<>(s, mutex);
1694 }
1695
1696 /**
1697 * @serial include
1698 */
1699 static class SynchronizedSet<E>
1700 extends SynchronizedCollection<E>
1701 implements Set<E> {
1702 private static final long serialVersionUID = 487447009682186044L;
1703
1704 SynchronizedSet(Set<E> s) {
1705 super(s);
1706 }
1707 SynchronizedSet(Set<E> s, Object mutex) {
1708 super(s, mutex);
1709 }
1710
1711 public boolean equals(Object o) {
1712 synchronized (mutex) {return c.equals(o);}
1713 }
1737 * or:
1738 * <pre>
1739 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
1740 * SortedSet s2 = s.headSet(foo);
1741 * ...
1742 * synchronized (s) { // Note: s, not s2!!!
1743 * Iterator i = s2.iterator(); // Must be in the synchronized block
1744 * while (i.hasNext())
1745 * foo(i.next());
1746 * }
1747 * </pre>
1748 * Failure to follow this advice may result in non-deterministic behavior.
1749 *
1750 * <p>The returned sorted set will be serializable if the specified
1751 * sorted set is serializable.
1752 *
1753 * @param s the sorted set to be "wrapped" in a synchronized sorted set.
1754 * @return a synchronized view of the specified sorted set.
1755 */
1756 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
1757 return new SynchronizedSortedSet<>(s);
1758 }
1759
1760 /**
1761 * @serial include
1762 */
1763 static class SynchronizedSortedSet<E>
1764 extends SynchronizedSet<E>
1765 implements SortedSet<E>
1766 {
1767 private static final long serialVersionUID = 8695801310862127406L;
1768
1769 private final SortedSet<E> ss;
1770
1771 SynchronizedSortedSet(SortedSet<E> s) {
1772 super(s);
1773 ss = s;
1774 }
1775 SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
1776 super(s, mutex);
1777 ss = s;
1778 }
1779
1780 public Comparator<? super E> comparator() {
1781 synchronized (mutex) {return ss.comparator();}
1782 }
1783
1784 public SortedSet<E> subSet(E fromElement, E toElement) {
1785 synchronized (mutex) {
1786 return new SynchronizedSortedSet<>(
1787 ss.subSet(fromElement, toElement), mutex);
1788 }
1789 }
1790 public SortedSet<E> headSet(E toElement) {
1791 synchronized (mutex) {
1792 return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
1793 }
1794 }
1795 public SortedSet<E> tailSet(E fromElement) {
1796 synchronized (mutex) {
1797 return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
1798 }
1799 }
1800
1801 public E first() {
1802 synchronized (mutex) {return ss.first();}
1803 }
1804 public E last() {
1805 synchronized (mutex) {return ss.last();}
1806 }
1807 }
1808
1809 /**
1810 * Returns a synchronized (thread-safe) list backed by the specified
1811 * list. In order to guarantee serial access, it is critical that
1812 * <strong>all</strong> access to the backing list is accomplished
1813 * through the returned list.<p>
1814 *
1815 * It is imperative that the user manually synchronize on the returned
1816 * list when iterating over it:
1817 * <pre>
1818 * List list = Collections.synchronizedList(new ArrayList());
1819 * ...
1820 * synchronized (list) {
1821 * Iterator i = list.iterator(); // Must be in synchronized block
1822 * while (i.hasNext())
1823 * foo(i.next());
1824 * }
1825 * </pre>
1826 * Failure to follow this advice may result in non-deterministic behavior.
1827 *
1828 * <p>The returned list will be serializable if the specified list is
1829 * serializable.
1830 *
1831 * @param list the list to be "wrapped" in a synchronized list.
1832 * @return a synchronized view of the specified list.
1833 */
1834 public static <T> List<T> synchronizedList(List<T> list) {
1835 return (list instanceof RandomAccess ?
1836 new SynchronizedRandomAccessList<>(list) :
1837 new SynchronizedList<>(list));
1838 }
1839
1840 static <T> List<T> synchronizedList(List<T> list, Object mutex) {
1841 return (list instanceof RandomAccess ?
1842 new SynchronizedRandomAccessList<>(list, mutex) :
1843 new SynchronizedList<>(list, mutex));
1844 }
1845
1846 /**
1847 * @serial include
1848 */
1849 static class SynchronizedList<E>
1850 extends SynchronizedCollection<E>
1851 implements List<E> {
1852 private static final long serialVersionUID = -7754090372962971524L;
1853
1854 final List<E> list;
1855
1856 SynchronizedList(List<E> list) {
1857 super(list);
1858 this.list = list;
1859 }
1860 SynchronizedList(List<E> list, Object mutex) {
1861 super(list, mutex);
1862 this.list = list;
1863 }
1886 synchronized (mutex) {return list.indexOf(o);}
1887 }
1888 public int lastIndexOf(Object o) {
1889 synchronized (mutex) {return list.lastIndexOf(o);}
1890 }
1891
1892 public boolean addAll(int index, Collection<? extends E> c) {
1893 synchronized (mutex) {return list.addAll(index, c);}
1894 }
1895
1896 public ListIterator<E> listIterator() {
1897 return list.listIterator(); // Must be manually synched by user
1898 }
1899
1900 public ListIterator<E> listIterator(int index) {
1901 return list.listIterator(index); // Must be manually synched by user
1902 }
1903
1904 public List<E> subList(int fromIndex, int toIndex) {
1905 synchronized (mutex) {
1906 return new SynchronizedList<>(list.subList(fromIndex, toIndex),
1907 mutex);
1908 }
1909 }
1910
1911 /**
1912 * SynchronizedRandomAccessList instances are serialized as
1913 * SynchronizedList instances to allow them to be deserialized
1914 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
1915 * This method inverts the transformation. As a beneficial
1916 * side-effect, it also grafts the RandomAccess marker onto
1917 * SynchronizedList instances that were serialized in pre-1.4 JREs.
1918 *
1919 * Note: Unfortunately, SynchronizedRandomAccessList instances
1920 * serialized in 1.4.1 and deserialized in 1.4 will become
1921 * SynchronizedList instances, as this method was missing in 1.4.
1922 */
1923 private Object readResolve() {
1924 return (list instanceof RandomAccess
1925 ? new SynchronizedRandomAccessList<>(list)
1926 : this);
1927 }
1928 }
1929
1930 /**
1931 * @serial include
1932 */
1933 static class SynchronizedRandomAccessList<E>
1934 extends SynchronizedList<E>
1935 implements RandomAccess {
1936
1937 SynchronizedRandomAccessList(List<E> list) {
1938 super(list);
1939 }
1940
1941 SynchronizedRandomAccessList(List<E> list, Object mutex) {
1942 super(list, mutex);
1943 }
1944
1945 public List<E> subList(int fromIndex, int toIndex) {
1946 synchronized (mutex) {
1947 return new SynchronizedRandomAccessList<>(
1948 list.subList(fromIndex, toIndex), mutex);
1949 }
1950 }
1951
1952 private static final long serialVersionUID = 1530674583602358482L;
1953
1954 /**
1955 * Allows instances to be deserialized in pre-1.4 JREs (which do
1956 * not have SynchronizedRandomAccessList). SynchronizedList has
1957 * a readResolve method that inverts this transformation upon
1958 * deserialization.
1959 */
1960 private Object writeReplace() {
1961 return new SynchronizedList<>(list);
1962 }
1963 }
1964
1965 /**
1966 * Returns a synchronized (thread-safe) map backed by the specified
1967 * map. In order to guarantee serial access, it is critical that
1968 * <strong>all</strong> access to the backing map is accomplished
1969 * through the returned map.<p>
1970 *
1971 * It is imperative that the user manually synchronize on the returned
1972 * map when iterating over any of its collection views:
1973 * <pre>
1974 * Map m = Collections.synchronizedMap(new HashMap());
1975 * ...
1976 * Set s = m.keySet(); // Needn't be in synchronized block
1977 * ...
1978 * synchronized (m) { // Synchronizing on m, not s!
1979 * Iterator i = s.iterator(); // Must be in synchronized block
1980 * while (i.hasNext())
1981 * foo(i.next());
1982 * }
1983 * </pre>
1984 * Failure to follow this advice may result in non-deterministic behavior.
1985 *
1986 * <p>The returned map will be serializable if the specified map is
1987 * serializable.
1988 *
1989 * @param m the map to be "wrapped" in a synchronized map.
1990 * @return a synchronized view of the specified map.
1991 */
1992 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
1993 return new SynchronizedMap<>(m);
1994 }
1995
1996 /**
1997 * @serial include
1998 */
1999 private static class SynchronizedMap<K,V>
2000 implements Map<K,V>, Serializable {
2001 private static final long serialVersionUID = 1978198479659022715L;
2002
2003 private final Map<K,V> m; // Backing Map
2004 final Object mutex; // Object on which to synchronize
2005
2006 SynchronizedMap(Map<K,V> m) {
2007 if (m==null)
2008 throw new NullPointerException();
2009 this.m = m;
2010 mutex = this;
2011 }
2012
2013 SynchronizedMap(Map<K,V> m, Object mutex) {
2034 public V put(K key, V value) {
2035 synchronized (mutex) {return m.put(key, value);}
2036 }
2037 public V remove(Object key) {
2038 synchronized (mutex) {return m.remove(key);}
2039 }
2040 public void putAll(Map<? extends K, ? extends V> map) {
2041 synchronized (mutex) {m.putAll(map);}
2042 }
2043 public void clear() {
2044 synchronized (mutex) {m.clear();}
2045 }
2046
2047 private transient Set<K> keySet = null;
2048 private transient Set<Map.Entry<K,V>> entrySet = null;
2049 private transient Collection<V> values = null;
2050
2051 public Set<K> keySet() {
2052 synchronized (mutex) {
2053 if (keySet==null)
2054 keySet = new SynchronizedSet<>(m.keySet(), mutex);
2055 return keySet;
2056 }
2057 }
2058
2059 public Set<Map.Entry<K,V>> entrySet() {
2060 synchronized (mutex) {
2061 if (entrySet==null)
2062 entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
2063 return entrySet;
2064 }
2065 }
2066
2067 public Collection<V> values() {
2068 synchronized (mutex) {
2069 if (values==null)
2070 values = new SynchronizedCollection<>(m.values(), mutex);
2071 return values;
2072 }
2073 }
2074
2075 public boolean equals(Object o) {
2076 synchronized (mutex) {return m.equals(o);}
2077 }
2078 public int hashCode() {
2079 synchronized (mutex) {return m.hashCode();}
2080 }
2081 public String toString() {
2082 synchronized (mutex) {return m.toString();}
2083 }
2084 private void writeObject(ObjectOutputStream s) throws IOException {
2085 synchronized (mutex) {s.defaultWriteObject();}
2086 }
2087 }
2088
2089 /**
2090 * Returns a synchronized (thread-safe) sorted map backed by the specified
2112 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2113 * SortedMap m2 = m.subMap(foo, bar);
2114 * ...
2115 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2116 * ...
2117 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2118 * Iterator i = s.iterator(); // Must be in synchronized block
2119 * while (i.hasNext())
2120 * foo(i.next());
2121 * }
2122 * </pre>
2123 * Failure to follow this advice may result in non-deterministic behavior.
2124 *
2125 * <p>The returned sorted map will be serializable if the specified
2126 * sorted map is serializable.
2127 *
2128 * @param m the sorted map to be "wrapped" in a synchronized sorted map.
2129 * @return a synchronized view of the specified sorted map.
2130 */
2131 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
2132 return new SynchronizedSortedMap<>(m);
2133 }
2134
2135
2136 /**
2137 * @serial include
2138 */
2139 static class SynchronizedSortedMap<K,V>
2140 extends SynchronizedMap<K,V>
2141 implements SortedMap<K,V>
2142 {
2143 private static final long serialVersionUID = -8798146769416483793L;
2144
2145 private final SortedMap<K,V> sm;
2146
2147 SynchronizedSortedMap(SortedMap<K,V> m) {
2148 super(m);
2149 sm = m;
2150 }
2151 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
2152 super(m, mutex);
2153 sm = m;
2154 }
2155
2156 public Comparator<? super K> comparator() {
2157 synchronized (mutex) {return sm.comparator();}
2158 }
2159
2160 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2161 synchronized (mutex) {
2162 return new SynchronizedSortedMap<>(
2163 sm.subMap(fromKey, toKey), mutex);
2164 }
2165 }
2166 public SortedMap<K,V> headMap(K toKey) {
2167 synchronized (mutex) {
2168 return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
2169 }
2170 }
2171 public SortedMap<K,V> tailMap(K fromKey) {
2172 synchronized (mutex) {
2173 return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
2174 }
2175 }
2176
2177 public K firstKey() {
2178 synchronized (mutex) {return sm.firstKey();}
2179 }
2180 public K lastKey() {
2181 synchronized (mutex) {return sm.lastKey();}
2182 }
2183 }
2184
2185 // Dynamically typesafe collection wrappers
2186
2187 /**
2188 * Returns a dynamically typesafe view of the specified collection.
2189 * Any attempt to insert an element of the wrong type will result in an
2190 * immediate {@link ClassCastException}. Assuming a collection
2191 * contains no incorrectly typed elements prior to the time a
2192 * dynamically typesafe view is generated, and that all subsequent
2193 * access to the collection takes place through the view, it is
2229 * operations through to the backing collection, but relies on
2230 * {@code Object}'s {@code equals} and {@code hashCode} methods. This
2231 * is necessary to preserve the contracts of these operations in the case
2232 * that the backing collection is a set or a list.
2233 *
2234 * <p>The returned collection will be serializable if the specified
2235 * collection is serializable.
2236 *
2237 * <p>Since {@code null} is considered to be a value of any reference
2238 * type, the returned collection permits insertion of null elements
2239 * whenever the backing collection does.
2240 *
2241 * @param c the collection for which a dynamically typesafe view is to be
2242 * returned
2243 * @param type the type of element that {@code c} is permitted to hold
2244 * @return a dynamically typesafe view of the specified collection
2245 * @since 1.5
2246 */
2247 public static <E> Collection<E> checkedCollection(Collection<E> c,
2248 Class<E> type) {
2249 return new CheckedCollection<>(c, type);
2250 }
2251
2252 @SuppressWarnings("unchecked")
2253 static <T> T[] zeroLengthArray(Class<T> type) {
2254 return (T[]) Array.newInstance(type, 0);
2255 }
2256
2257 /**
2258 * @serial include
2259 */
2260 static class CheckedCollection<E> implements Collection<E>, Serializable {
2261 private static final long serialVersionUID = 1578914078182001775L;
2262
2263 final Collection<E> c;
2264 final Class<E> type;
2265
2266 void typeCheck(Object o) {
2267 if (o != null && !type.isInstance(o))
2268 throw new ClassCastException(badElementMsg(o));
2269 }
2361 * set cannot contain an incorrectly typed element.
2362 *
2363 * <p>A discussion of the use of dynamically typesafe views may be
2364 * found in the documentation for the {@link #checkedCollection
2365 * checkedCollection} method.
2366 *
2367 * <p>The returned set will be serializable if the specified set is
2368 * serializable.
2369 *
2370 * <p>Since {@code null} is considered to be a value of any reference
2371 * type, the returned set permits insertion of null elements whenever
2372 * the backing set does.
2373 *
2374 * @param s the set for which a dynamically typesafe view is to be
2375 * returned
2376 * @param type the type of element that {@code s} is permitted to hold
2377 * @return a dynamically typesafe view of the specified set
2378 * @since 1.5
2379 */
2380 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
2381 return new CheckedSet<>(s, type);
2382 }
2383
2384 /**
2385 * @serial include
2386 */
2387 static class CheckedSet<E> extends CheckedCollection<E>
2388 implements Set<E>, Serializable
2389 {
2390 private static final long serialVersionUID = 4694047833775013803L;
2391
2392 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
2393
2394 public boolean equals(Object o) { return o == this || c.equals(o); }
2395 public int hashCode() { return c.hashCode(); }
2396 }
2397
2398 /**
2399 * Returns a dynamically typesafe view of the specified sorted set.
2400 * Any attempt to insert an element of the wrong type will result in an
2401 * immediate {@link ClassCastException}. Assuming a sorted set
2407 *
2408 * <p>A discussion of the use of dynamically typesafe views may be
2409 * found in the documentation for the {@link #checkedCollection
2410 * checkedCollection} method.
2411 *
2412 * <p>The returned sorted set will be serializable if the specified sorted
2413 * set is serializable.
2414 *
2415 * <p>Since {@code null} is considered to be a value of any reference
2416 * type, the returned sorted set permits insertion of null elements
2417 * whenever the backing sorted set does.
2418 *
2419 * @param s the sorted set for which a dynamically typesafe view is to be
2420 * returned
2421 * @param type the type of element that {@code s} is permitted to hold
2422 * @return a dynamically typesafe view of the specified sorted set
2423 * @since 1.5
2424 */
2425 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
2426 Class<E> type) {
2427 return new CheckedSortedSet<>(s, type);
2428 }
2429
2430 /**
2431 * @serial include
2432 */
2433 static class CheckedSortedSet<E> extends CheckedSet<E>
2434 implements SortedSet<E>, Serializable
2435 {
2436 private static final long serialVersionUID = 1599911165492914959L;
2437 private final SortedSet<E> ss;
2438
2439 CheckedSortedSet(SortedSet<E> s, Class<E> type) {
2440 super(s, type);
2441 ss = s;
2442 }
2443
2444 public Comparator<? super E> comparator() { return ss.comparator(); }
2445 public E first() { return ss.first(); }
2446 public E last() { return ss.last(); }
2447
2467 *
2468 * <p>A discussion of the use of dynamically typesafe views may be
2469 * found in the documentation for the {@link #checkedCollection
2470 * checkedCollection} method.
2471 *
2472 * <p>The returned list will be serializable if the specified list
2473 * is serializable.
2474 *
2475 * <p>Since {@code null} is considered to be a value of any reference
2476 * type, the returned list permits insertion of null elements whenever
2477 * the backing list does.
2478 *
2479 * @param list the list for which a dynamically typesafe view is to be
2480 * returned
2481 * @param type the type of element that {@code list} is permitted to hold
2482 * @return a dynamically typesafe view of the specified list
2483 * @since 1.5
2484 */
2485 public static <E> List<E> checkedList(List<E> list, Class<E> type) {
2486 return (list instanceof RandomAccess ?
2487 new CheckedRandomAccessList<>(list, type) :
2488 new CheckedList<>(list, type));
2489 }
2490
2491 /**
2492 * @serial include
2493 */
2494 static class CheckedList<E>
2495 extends CheckedCollection<E>
2496 implements List<E>
2497 {
2498 private static final long serialVersionUID = 65247728283967356L;
2499 final List<E> list;
2500
2501 CheckedList(List<E> list, Class<E> type) {
2502 super(list, type);
2503 this.list = list;
2504 }
2505
2506 public boolean equals(Object o) { return o == this || list.equals(o); }
2507 public int hashCode() { return list.hashCode(); }
2508 public E get(int index) { return list.get(index); }
2533 public E next() { return i.next(); }
2534 public boolean hasPrevious() { return i.hasPrevious(); }
2535 public E previous() { return i.previous(); }
2536 public int nextIndex() { return i.nextIndex(); }
2537 public int previousIndex() { return i.previousIndex(); }
2538 public void remove() { i.remove(); }
2539
2540 public void set(E e) {
2541 typeCheck(e);
2542 i.set(e);
2543 }
2544
2545 public void add(E e) {
2546 typeCheck(e);
2547 i.add(e);
2548 }
2549 };
2550 }
2551
2552 public List<E> subList(int fromIndex, int toIndex) {
2553 return new CheckedList<>(list.subList(fromIndex, toIndex), type);
2554 }
2555 }
2556
2557 /**
2558 * @serial include
2559 */
2560 static class CheckedRandomAccessList<E> extends CheckedList<E>
2561 implements RandomAccess
2562 {
2563 private static final long serialVersionUID = 1638200125423088369L;
2564
2565 CheckedRandomAccessList(List<E> list, Class<E> type) {
2566 super(list, type);
2567 }
2568
2569 public List<E> subList(int fromIndex, int toIndex) {
2570 return new CheckedRandomAccessList<>(
2571 list.subList(fromIndex, toIndex), type);
2572 }
2573 }
2574
2575 /**
2576 * Returns a dynamically typesafe view of the specified map.
2577 * Any attempt to insert a mapping whose key or value have the wrong
2578 * type will result in an immediate {@link ClassCastException}.
2579 * Similarly, any attempt to modify the value currently associated with
2580 * a key will result in an immediate {@link ClassCastException},
2581 * whether the modification is attempted directly through the map
2582 * itself, or through a {@link Map.Entry} instance obtained from the
2583 * map's {@link Map#entrySet() entry set} view.
2584 *
2585 * <p>Assuming a map contains no incorrectly typed keys or values
2586 * prior to the time a dynamically typesafe view is generated, and
2587 * that all subsequent access to the map takes place through the view
2588 * (or one of its collection views), it is <i>guaranteed</i> that the
2589 * map cannot contain an incorrectly typed key or value.
2590 *
2592 * found in the documentation for the {@link #checkedCollection
2593 * checkedCollection} method.
2594 *
2595 * <p>The returned map will be serializable if the specified map is
2596 * serializable.
2597 *
2598 * <p>Since {@code null} is considered to be a value of any reference
2599 * type, the returned map permits insertion of null keys or values
2600 * whenever the backing map does.
2601 *
2602 * @param m the map for which a dynamically typesafe view is to be
2603 * returned
2604 * @param keyType the type of key that {@code m} is permitted to hold
2605 * @param valueType the type of value that {@code m} is permitted to hold
2606 * @return a dynamically typesafe view of the specified map
2607 * @since 1.5
2608 */
2609 public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
2610 Class<K> keyType,
2611 Class<V> valueType) {
2612 return new CheckedMap<>(m, keyType, valueType);
2613 }
2614
2615
2616 /**
2617 * @serial include
2618 */
2619 private static class CheckedMap<K,V>
2620 implements Map<K,V>, Serializable
2621 {
2622 private static final long serialVersionUID = 5742860141034234728L;
2623
2624 private final Map<K, V> m;
2625 final Class<K> keyType;
2626 final Class<V> valueType;
2627
2628 private void typeCheck(Object key, Object value) {
2629 if (key != null && !keyType.isInstance(key))
2630 throw new ClassCastException(badKeyMsg(key));
2631
2632 if (value != null && !valueType.isInstance(value))
2661 public Set<K> keySet() { return m.keySet(); }
2662 public Collection<V> values() { return m.values(); }
2663 public boolean equals(Object o) { return o == this || m.equals(o); }
2664 public int hashCode() { return m.hashCode(); }
2665 public String toString() { return m.toString(); }
2666
2667 public V put(K key, V value) {
2668 typeCheck(key, value);
2669 return m.put(key, value);
2670 }
2671
2672 @SuppressWarnings("unchecked")
2673 public void putAll(Map<? extends K, ? extends V> t) {
2674 // Satisfy the following goals:
2675 // - good diagnostics in case of type mismatch
2676 // - all-or-nothing semantics
2677 // - protection from malicious t
2678 // - correct behavior if t is a concurrent map
2679 Object[] entries = t.entrySet().toArray();
2680 List<Map.Entry<K,V>> checked =
2681 new ArrayList<>(entries.length);
2682 for (Object o : entries) {
2683 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
2684 Object k = e.getKey();
2685 Object v = e.getValue();
2686 typeCheck(k, v);
2687 checked.add(
2688 new AbstractMap.SimpleImmutableEntry<>((K) k, (V) v));
2689 }
2690 for (Map.Entry<K,V> e : checked)
2691 m.put(e.getKey(), e.getValue());
2692 }
2693
2694 private transient Set<Map.Entry<K,V>> entrySet = null;
2695
2696 public Set<Map.Entry<K,V>> entrySet() {
2697 if (entrySet==null)
2698 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType);
2699 return entrySet;
2700 }
2701
2702 /**
2703 * We need this class in addition to CheckedSet as Map.Entry permits
2704 * modification of the backing Map via the setValue operation. This
2705 * class is subtle: there are many possible attacks that must be
2706 * thwarted.
2707 *
2708 * @serial exclude
2709 */
2710 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
2711 private final Set<Map.Entry<K,V>> s;
2712 private final Class<V> valueType;
2713
2714 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
2715 this.s = s;
2716 this.valueType = valueType;
2717 }
2718
2793 return s.contains(
2794 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
2795 }
2796
2797 /**
2798 * The bulk collection methods are overridden to protect
2799 * against an unscrupulous collection whose contains(Object o)
2800 * method senses when o is a Map.Entry, and calls o.setValue.
2801 */
2802 public boolean containsAll(Collection<?> c) {
2803 for (Object o : c)
2804 if (!contains(o)) // Invokes safe contains() above
2805 return false;
2806 return true;
2807 }
2808
2809 public boolean remove(Object o) {
2810 if (!(o instanceof Map.Entry))
2811 return false;
2812 return s.remove(new AbstractMap.SimpleImmutableEntry
2813 <>((Map.Entry<?,?>)o));
2814 }
2815
2816 public boolean removeAll(Collection<?> c) {
2817 return batchRemove(c, false);
2818 }
2819 public boolean retainAll(Collection<?> c) {
2820 return batchRemove(c, true);
2821 }
2822 private boolean batchRemove(Collection<?> c, boolean complement) {
2823 boolean modified = false;
2824 Iterator<Map.Entry<K,V>> it = iterator();
2825 while (it.hasNext()) {
2826 if (c.contains(it.next()) != complement) {
2827 it.remove();
2828 modified = true;
2829 }
2830 }
2831 return modified;
2832 }
2833
2834 public boolean equals(Object o) {
2835 if (o == this)
2836 return true;
2837 if (!(o instanceof Set))
2838 return false;
2839 Set<?> that = (Set<?>) o;
2840 return that.size() == s.size()
2841 && containsAll(that); // Invokes safe containsAll() above
2842 }
2843
2844 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
2845 Class<T> valueType) {
2846 return new CheckedEntry<>(e, valueType);
2847 }
2848
2849 /**
2850 * This "wrapper class" serves two purposes: it prevents
2851 * the client from modifying the backing Map, by short-circuiting
2852 * the setValue method, and it protects the backing Map against
2853 * an ill-behaved Map.Entry that attempts to modify another
2854 * Map.Entry when asked to perform an equality check.
2855 */
2856 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
2857 private final Map.Entry<K, V> e;
2858 private final Class<T> valueType;
2859
2860 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
2861 this.e = e;
2862 this.valueType = valueType;
2863 }
2864
2865 public K getKey() { return e.getKey(); }
2866 public V getValue() { return e.getValue(); }
2867 public int hashCode() { return e.hashCode(); }
2868 public String toString() { return e.toString(); }
2869
2870 public V setValue(V value) {
2871 if (value != null && !valueType.isInstance(value))
2872 throw new ClassCastException(badValueMsg(value));
2873 return e.setValue(value);
2874 }
2875
2876 private String badValueMsg(Object value) {
2877 return "Attempt to insert " + value.getClass() +
2878 " value into map with value type " + valueType;
2879 }
2880
2881 public boolean equals(Object o) {
2882 if (o == this)
2883 return true;
2884 if (!(o instanceof Map.Entry))
2885 return false;
2886 return e.equals(new AbstractMap.SimpleImmutableEntry
2887 <>((Map.Entry<?,?>)o));
2888 }
2889 }
2890 }
2891 }
2892
2893 /**
2894 * Returns a dynamically typesafe view of the specified sorted map.
2895 * Any attempt to insert a mapping whose key or value have the wrong
2896 * type will result in an immediate {@link ClassCastException}.
2897 * Similarly, any attempt to modify the value currently associated with
2898 * a key will result in an immediate {@link ClassCastException},
2899 * whether the modification is attempted directly through the map
2900 * itself, or through a {@link Map.Entry} instance obtained from the
2901 * map's {@link Map#entrySet() entry set} view.
2902 *
2903 * <p>Assuming a map contains no incorrectly typed keys or values
2904 * prior to the time a dynamically typesafe view is generated, and
2905 * that all subsequent access to the map takes place through the view
2906 * (or one of its collection views), it is <i>guaranteed</i> that the
2907 * map cannot contain an incorrectly typed key or value.
2910 * found in the documentation for the {@link #checkedCollection
2911 * checkedCollection} method.
2912 *
2913 * <p>The returned map will be serializable if the specified map is
2914 * serializable.
2915 *
2916 * <p>Since {@code null} is considered to be a value of any reference
2917 * type, the returned map permits insertion of null keys or values
2918 * whenever the backing map does.
2919 *
2920 * @param m the map for which a dynamically typesafe view is to be
2921 * returned
2922 * @param keyType the type of key that {@code m} is permitted to hold
2923 * @param valueType the type of value that {@code m} is permitted to hold
2924 * @return a dynamically typesafe view of the specified map
2925 * @since 1.5
2926 */
2927 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
2928 Class<K> keyType,
2929 Class<V> valueType) {
2930 return new CheckedSortedMap<>(m, keyType, valueType);
2931 }
2932
2933 /**
2934 * @serial include
2935 */
2936 static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
2937 implements SortedMap<K,V>, Serializable
2938 {
2939 private static final long serialVersionUID = 1599671320688067438L;
2940
2941 private final SortedMap<K, V> sm;
2942
2943 CheckedSortedMap(SortedMap<K, V> m,
2944 Class<K> keyType, Class<V> valueType) {
2945 super(m, keyType, valueType);
2946 sm = m;
2947 }
2948
2949 public Comparator<? super K> comparator() { return sm.comparator(); }
2950 public K firstKey() { return sm.firstKey(); }
2976 * NoSuchElementException}.
2977 *
2978 * <li>{@link Iterator#remove remove} always throws {@link
2979 * IllegalStateException}.
2980 *
2981 * </ul>
2982 *
2983 * <p>Implementations of this method are permitted, but not
2984 * required, to return the same object from multiple invocations.
2985 *
2986 * @return an empty iterator
2987 * @since 1.7
2988 */
2989 @SuppressWarnings("unchecked")
2990 public static <T> Iterator<T> emptyIterator() {
2991 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
2992 }
2993
2994 private static class EmptyIterator<E> implements Iterator<E> {
2995 static final EmptyIterator<Object> EMPTY_ITERATOR
2996 = new EmptyIterator<>();
2997
2998 public boolean hasNext() { return false; }
2999 public E next() { throw new NoSuchElementException(); }
3000 public void remove() { throw new IllegalStateException(); }
3001 }
3002
3003 /**
3004 * Returns a list iterator that has no elements. More precisely,
3005 *
3006 * <ul compact>
3007 *
3008 * <li>{@link Iterator#hasNext hasNext} and {@link
3009 * ListIterator#hasPrevious hasPrevious} always return {@code
3010 * false}.
3011 *
3012 * <li>{@link Iterator#next next} and {@link ListIterator#previous
3013 * previous} always throw {@link NoSuchElementException}.
3014 *
3015 * <li>{@link Iterator#remove remove} and {@link ListIterator#set
3016 * set} always throw {@link IllegalStateException}.
3025 * returns {@code -1}.
3026 *
3027 * </ul>
3028 *
3029 * <p>Implementations of this method are permitted, but not
3030 * required, to return the same object from multiple invocations.
3031 *
3032 * @return an empty list iterator
3033 * @since 1.7
3034 */
3035 @SuppressWarnings("unchecked")
3036 public static <T> ListIterator<T> emptyListIterator() {
3037 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
3038 }
3039
3040 private static class EmptyListIterator<E>
3041 extends EmptyIterator<E>
3042 implements ListIterator<E>
3043 {
3044 static final EmptyListIterator<Object> EMPTY_ITERATOR
3045 = new EmptyListIterator<>();
3046
3047 public boolean hasPrevious() { return false; }
3048 public E previous() { throw new NoSuchElementException(); }
3049 public int nextIndex() { return 0; }
3050 public int previousIndex() { return -1; }
3051 public void set(E e) { throw new IllegalStateException(); }
3052 public void add(E e) { throw new UnsupportedOperationException(); }
3053 }
3054
3055 /**
3056 * Returns an enumeration that has no elements. More precisely,
3057 *
3058 * <ul compact>
3059 *
3060 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always
3061 * returns {@code false}.
3062 *
3063 * <li> {@link Enumeration#nextElement nextElement} always throws
3064 * {@link NoSuchElementException}.
3065 *
3066 * </ul>
3067 *
3068 * <p>Implementations of this method are permitted, but not
3069 * required, to return the same object from multiple invocations.
3070 *
3071 * @return an empty enumeration
3072 * @since 1.7
3073 */
3074 @SuppressWarnings("unchecked")
3075 public static <T> Enumeration<T> emptyEnumeration() {
3076 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
3077 }
3078
3079 private static class EmptyEnumeration<E> implements Enumeration<E> {
3080 static final EmptyEnumeration<Object> EMPTY_ENUMERATION
3081 = new EmptyEnumeration<>();
3082
3083 public boolean hasMoreElements() { return false; }
3084 public E nextElement() { throw new NoSuchElementException(); }
3085 }
3086
3087 /**
3088 * The empty set (immutable). This set is serializable.
3089 *
3090 * @see #emptySet()
3091 */
3092 @SuppressWarnings("unchecked")
3093 public static final Set EMPTY_SET = new EmptySet<>();
3094
3095 /**
3096 * Returns the empty set (immutable). This set is serializable.
3097 * Unlike the like-named field, this method is parameterized.
3098 *
3099 * <p>This example illustrates the type-safe way to obtain an empty set:
3100 * <pre>
3101 * Set<String> s = Collections.emptySet();
3102 * </pre>
3103 * Implementation note: Implementations of this method need not
3104 * create a separate <tt>Set</tt> object for each call. Using this
3105 * method is likely to have comparable cost to using the like-named
3106 * field. (Unlike this method, the field does not provide type safety.)
3107 *
3108 * @see #EMPTY_SET
3109 * @since 1.5
3110 */
3111 @SuppressWarnings("unchecked")
3112 public static final <T> Set<T> emptySet() {
3113 return (Set<T>) EMPTY_SET;
3133 public Object[] toArray() { return new Object[0]; }
3134
3135 public <T> T[] toArray(T[] a) {
3136 if (a.length > 0)
3137 a[0] = null;
3138 return a;
3139 }
3140
3141 // Preserves singleton property
3142 private Object readResolve() {
3143 return EMPTY_SET;
3144 }
3145 }
3146
3147 /**
3148 * The empty list (immutable). This list is serializable.
3149 *
3150 * @see #emptyList()
3151 */
3152 @SuppressWarnings("unchecked")
3153 public static final List EMPTY_LIST = new EmptyList<>();
3154
3155 /**
3156 * Returns the empty list (immutable). This list is serializable.
3157 *
3158 * <p>This example illustrates the type-safe way to obtain an empty list:
3159 * <pre>
3160 * List<String> s = Collections.emptyList();
3161 * </pre>
3162 * Implementation note: Implementations of this method need not
3163 * create a separate <tt>List</tt> object for each call. Using this
3164 * method is likely to have comparable cost to using the like-named
3165 * field. (Unlike this method, the field does not provide type safety.)
3166 *
3167 * @see #EMPTY_LIST
3168 * @since 1.5
3169 */
3170 @SuppressWarnings("unchecked")
3171 public static final <T> List<T> emptyList() {
3172 return (List<T>) EMPTY_LIST;
3173 }
3207
3208 public boolean equals(Object o) {
3209 return (o instanceof List) && ((List<?>)o).isEmpty();
3210 }
3211
3212 public int hashCode() { return 1; }
3213
3214 // Preserves singleton property
3215 private Object readResolve() {
3216 return EMPTY_LIST;
3217 }
3218 }
3219
3220 /**
3221 * The empty map (immutable). This map is serializable.
3222 *
3223 * @see #emptyMap()
3224 * @since 1.3
3225 */
3226 @SuppressWarnings("unchecked")
3227 public static final Map EMPTY_MAP = new EmptyMap<>();
3228
3229 /**
3230 * Returns the empty map (immutable). This map is serializable.
3231 *
3232 * <p>This example illustrates the type-safe way to obtain an empty set:
3233 * <pre>
3234 * Map<String, Date> s = Collections.emptyMap();
3235 * </pre>
3236 * Implementation note: Implementations of this method need not
3237 * create a separate <tt>Map</tt> object for each call. Using this
3238 * method is likely to have comparable cost to using the like-named
3239 * field. (Unlike this method, the field does not provide type safety.)
3240 *
3241 * @see #EMPTY_MAP
3242 * @since 1.5
3243 */
3244 @SuppressWarnings("unchecked")
3245 public static final <K,V> Map<K,V> emptyMap() {
3246 return (Map<K,V>) EMPTY_MAP;
3247 }
3269 }
3270
3271 public int hashCode() {return 0;}
3272
3273 // Preserves singleton property
3274 private Object readResolve() {
3275 return EMPTY_MAP;
3276 }
3277 }
3278
3279 // Singleton collections
3280
3281 /**
3282 * Returns an immutable set containing only the specified object.
3283 * The returned set is serializable.
3284 *
3285 * @param o the sole object to be stored in the returned set.
3286 * @return an immutable set containing only the specified object.
3287 */
3288 public static <T> Set<T> singleton(T o) {
3289 return new SingletonSet<>(o);
3290 }
3291
3292 static <E> Iterator<E> singletonIterator(final E e) {
3293 return new Iterator<E>() {
3294 private boolean hasNext = true;
3295 public boolean hasNext() {
3296 return hasNext;
3297 }
3298 public E next() {
3299 if (hasNext) {
3300 hasNext = false;
3301 return e;
3302 }
3303 throw new NoSuchElementException();
3304 }
3305 public void remove() {
3306 throw new UnsupportedOperationException();
3307 }
3308 };
3309 }
3322 SingletonSet(E e) {element = e;}
3323
3324 public Iterator<E> iterator() {
3325 return singletonIterator(element);
3326 }
3327
3328 public int size() {return 1;}
3329
3330 public boolean contains(Object o) {return eq(o, element);}
3331 }
3332
3333 /**
3334 * Returns an immutable list containing only the specified object.
3335 * The returned list is serializable.
3336 *
3337 * @param o the sole object to be stored in the returned list.
3338 * @return an immutable list containing only the specified object.
3339 * @since 1.3
3340 */
3341 public static <T> List<T> singletonList(T o) {
3342 return new SingletonList<>(o);
3343 }
3344
3345 /**
3346 * @serial include
3347 */
3348 private static class SingletonList<E>
3349 extends AbstractList<E>
3350 implements RandomAccess, Serializable {
3351
3352 private static final long serialVersionUID = 3093736618740652951L;
3353
3354 private final E element;
3355
3356 SingletonList(E obj) {element = obj;}
3357
3358 public Iterator<E> iterator() {
3359 return singletonIterator(element);
3360 }
3361
3362 public int size() {return 1;}
3364 public boolean contains(Object obj) {return eq(obj, element);}
3365
3366 public E get(int index) {
3367 if (index != 0)
3368 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
3369 return element;
3370 }
3371 }
3372
3373 /**
3374 * Returns an immutable map, mapping only the specified key to the
3375 * specified value. The returned map is serializable.
3376 *
3377 * @param key the sole key to be stored in the returned map.
3378 * @param value the value to which the returned map maps <tt>key</tt>.
3379 * @return an immutable map containing only the specified key-value
3380 * mapping.
3381 * @since 1.3
3382 */
3383 public static <K,V> Map<K,V> singletonMap(K key, V value) {
3384 return new SingletonMap<>(key, value);
3385 }
3386
3387 /**
3388 * @serial include
3389 */
3390 private static class SingletonMap<K,V>
3391 extends AbstractMap<K,V>
3392 implements Serializable {
3393 private static final long serialVersionUID = -6979724477215052911L;
3394
3395 private final K k;
3396 private final V v;
3397
3398 SingletonMap(K key, V value) {
3399 k = key;
3400 v = value;
3401 }
3402
3403 public int size() {return 1;}
3404
3406
3407 public boolean containsKey(Object key) {return eq(key, k);}
3408
3409 public boolean containsValue(Object value) {return eq(value, v);}
3410
3411 public V get(Object key) {return (eq(key, k) ? v : null);}
3412
3413 private transient Set<K> keySet = null;
3414 private transient Set<Map.Entry<K,V>> entrySet = null;
3415 private transient Collection<V> values = null;
3416
3417 public Set<K> keySet() {
3418 if (keySet==null)
3419 keySet = singleton(k);
3420 return keySet;
3421 }
3422
3423 public Set<Map.Entry<K,V>> entrySet() {
3424 if (entrySet==null)
3425 entrySet = Collections.<Map.Entry<K,V>>singleton(
3426 new SimpleImmutableEntry<>(k, v));
3427 return entrySet;
3428 }
3429
3430 public Collection<V> values() {
3431 if (values==null)
3432 values = singleton(v);
3433 return values;
3434 }
3435
3436 }
3437
3438 // Miscellaneous
3439
3440 /**
3441 * Returns an immutable list consisting of <tt>n</tt> copies of the
3442 * specified object. The newly allocated data object is tiny (it contains
3443 * a single reference to the data object). This method is useful in
3444 * combination with the <tt>List.addAll</tt> method to grow lists.
3445 * The returned list is serializable.
3446 *
3447 * @param n the number of elements in the returned list.
3448 * @param o the element to appear repeatedly in the returned list.
3449 * @return an immutable list consisting of <tt>n</tt> copies of the
3450 * specified object.
3451 * @throws IllegalArgumentException if {@code n < 0}
3452 * @see List#addAll(Collection)
3453 * @see List#addAll(int, Collection)
3454 */
3455 public static <T> List<T> nCopies(int n, T o) {
3456 if (n < 0)
3457 throw new IllegalArgumentException("List length = " + n);
3458 return new CopiesList<>(n, o);
3459 }
3460
3461 /**
3462 * @serial include
3463 */
3464 private static class CopiesList<E>
3465 extends AbstractList<E>
3466 implements RandomAccess, Serializable
3467 {
3468 private static final long serialVersionUID = 2739099268398711800L;
3469
3470 final int n;
3471 final E element;
3472
3473 CopiesList(int n, E e) {
3474 assert n >= 0;
3475 this.n = n;
3476 element = e;
3477 }
3478
3512 a = (T[])java.lang.reflect.Array
3513 .newInstance(a.getClass().getComponentType(), n);
3514 if (element != null)
3515 Arrays.fill(a, 0, n, element);
3516 } else {
3517 Arrays.fill(a, 0, n, element);
3518 if (a.length > n)
3519 a[n] = null;
3520 }
3521 return a;
3522 }
3523
3524 public List<E> subList(int fromIndex, int toIndex) {
3525 if (fromIndex < 0)
3526 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
3527 if (toIndex > n)
3528 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
3529 if (fromIndex > toIndex)
3530 throw new IllegalArgumentException("fromIndex(" + fromIndex +
3531 ") > toIndex(" + toIndex + ")");
3532 return new CopiesList<>(toIndex - fromIndex, element);
3533 }
3534 }
3535
3536 /**
3537 * Returns a comparator that imposes the reverse of the <i>natural
3538 * ordering</i> on a collection of objects that implement the
3539 * <tt>Comparable</tt> interface. (The natural ordering is the ordering
3540 * imposed by the objects' own <tt>compareTo</tt> method.) This enables a
3541 * simple idiom for sorting (or maintaining) collections (or arrays) of
3542 * objects that implement the <tt>Comparable</tt> interface in
3543 * reverse-natural-order. For example, suppose a is an array of
3544 * strings. Then: <pre>
3545 * Arrays.sort(a, Collections.reverseOrder());
3546 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p>
3547 *
3548 * The returned comparator is serializable.
3549 *
3550 * @return a comparator that imposes the reverse of the <i>natural
3551 * ordering</i> on a collection of objects that implement
3552 * the <tt>Comparable</tt> interface.
3578 * Returns a comparator that imposes the reverse ordering of the specified
3579 * comparator. If the specified comparator is null, this method is
3580 * equivalent to {@link #reverseOrder()} (in other words, it returns a
3581 * comparator that imposes the reverse of the <i>natural ordering</i> on a
3582 * collection of objects that implement the Comparable interface).
3583 *
3584 * <p>The returned comparator is serializable (assuming the specified
3585 * comparator is also serializable or null).
3586 *
3587 * @return a comparator that imposes the reverse ordering of the
3588 * specified comparator
3589 * @since 1.5
3590 */
3591 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
3592 if (cmp == null)
3593 return reverseOrder();
3594
3595 if (cmp instanceof ReverseComparator2)
3596 return ((ReverseComparator2<T>)cmp).cmp;
3597
3598 return new ReverseComparator2<>(cmp);
3599 }
3600
3601 /**
3602 * @serial include
3603 */
3604 private static class ReverseComparator2<T> implements Comparator<T>,
3605 Serializable
3606 {
3607 private static final long serialVersionUID = 4374092139857L;
3608
3609 /**
3610 * The comparator specified in the static factory. This will never
3611 * be null, as the static factory returns a ReverseComparator
3612 * instance if its argument is null.
3613 *
3614 * @serial
3615 */
3616 final Comparator<T> cmp;
3617
3618 ReverseComparator2(Comparator<T> cmp) {
3657 }
3658 };
3659 }
3660
3661 /**
3662 * Returns an array list containing the elements returned by the
3663 * specified enumeration in the order they are returned by the
3664 * enumeration. This method provides interoperability between
3665 * legacy APIs that return enumerations and new APIs that require
3666 * collections.
3667 *
3668 * @param e enumeration providing elements for the returned
3669 * array list
3670 * @return an array list containing the elements returned
3671 * by the specified enumeration.
3672 * @since 1.4
3673 * @see Enumeration
3674 * @see ArrayList
3675 */
3676 public static <T> ArrayList<T> list(Enumeration<T> e) {
3677 ArrayList<T> l = new ArrayList<>();
3678 while (e.hasMoreElements())
3679 l.add(e.nextElement());
3680 return l;
3681 }
3682
3683 /**
3684 * Returns true if the specified arguments are equal, or both null.
3685 */
3686 static boolean eq(Object o1, Object o2) {
3687 return o1==null ? o2==null : o1.equals(o2);
3688 }
3689
3690 /**
3691 * Returns the number of elements in the specified collection equal to the
3692 * specified object. More formally, returns the number of elements
3693 * <tt>e</tt> in the collection such that
3694 * <tt>(o == null ? e == null : o.equals(e))</tt>.
3695 *
3696 * @param c the collection in which to determine the frequency
3697 * of <tt>o</tt>
3802 * exactly one method invocation on the backing map or its <tt>keySet</tt>
3803 * view, with one exception. The <tt>addAll</tt> method is implemented
3804 * as a sequence of <tt>put</tt> invocations on the backing map.
3805 *
3806 * <p>The specified map must be empty at the time this method is invoked,
3807 * and should not be accessed directly after this method returns. These
3808 * conditions are ensured if the map is created empty, passed directly
3809 * to this method, and no reference to the map is retained, as illustrated
3810 * in the following code fragment:
3811 * <pre>
3812 * Set<Object> weakHashSet = Collections.newSetFromMap(
3813 * new WeakHashMap<Object, Boolean>());
3814 * </pre>
3815 *
3816 * @param map the backing map
3817 * @return the set backed by the map
3818 * @throws IllegalArgumentException if <tt>map</tt> is not empty
3819 * @since 1.6
3820 */
3821 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
3822 return new SetFromMap<>(map);
3823 }
3824
3825 /**
3826 * @serial include
3827 */
3828 private static class SetFromMap<E> extends AbstractSet<E>
3829 implements Set<E>, Serializable
3830 {
3831 private final Map<E, Boolean> m; // The backing map
3832 private transient Set<E> s; // Its keySet
3833
3834 SetFromMap(Map<E, Boolean> map) {
3835 if (!map.isEmpty())
3836 throw new IllegalArgumentException("Map is non-empty");
3837 m = map;
3838 s = map.keySet();
3839 }
3840
3841 public void clear() { m.clear(); }
3842 public int size() { return m.size(); }
3866 }
3867
3868 /**
3869 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo)
3870 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>,
3871 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This
3872 * view can be useful when you would like to use a method
3873 * requiring a <tt>Queue</tt> but you need Lifo ordering.
3874 *
3875 * <p>Each method invocation on the queue returned by this method
3876 * results in exactly one method invocation on the backing deque, with
3877 * one exception. The {@link Queue#addAll addAll} method is
3878 * implemented as a sequence of {@link Deque#addFirst addFirst}
3879 * invocations on the backing deque.
3880 *
3881 * @param deque the deque
3882 * @return the queue
3883 * @since 1.6
3884 */
3885 public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
3886 return new AsLIFOQueue<>(deque);
3887 }
3888
3889 /**
3890 * @serial include
3891 */
3892 static class AsLIFOQueue<E> extends AbstractQueue<E>
3893 implements Queue<E>, Serializable {
3894 private static final long serialVersionUID = 1802017725587941708L;
3895 private final Deque<E> q;
3896 AsLIFOQueue(Deque<E> q) { this.q = q; }
3897 public boolean add(E e) { q.addFirst(e); return true; }
3898 public boolean offer(E e) { return q.offerFirst(e); }
3899 public E poll() { return q.pollFirst(); }
3900 public E remove() { return q.removeFirst(); }
3901 public E peek() { return q.peekFirst(); }
3902 public E element() { return q.getFirst(); }
3903 public void clear() { q.clear(); }
3904 public int size() { return q.size(); }
3905 public boolean isEmpty() { return q.isEmpty(); }
3906 public boolean contains(Object o) { return q.contains(o); }
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