1 /*
2 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package sun.awt.util;
27
28 import java.util.AbstractList;
29 import java.util.Arrays;
30 import java.util.Collection;
31 import java.util.ConcurrentModificationException;
32 import java.util.List;
33 import java.util.RandomAccess;
34
35 /**
36 * Resizable-array implementation of the <tt>List</tt> interface. Implements
37 * all optional list operations, and permits all elements, including
38 * <tt>null</tt>. In addition to implementing the <tt>List</tt> interface,
39 * this class provides methods to manipulate the size of the array that is
40 * used internally to store the list. (This class is roughly equivalent to
41 * <tt>Vector</tt>, except that it is unsynchronized.)<p>
42 *
43 * The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>,
44 * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant
45 * time. The <tt>add</tt> operation runs in <i>amortized constant time</i>,
46 * that is, adding n elements requires O(n) time. All of the other operations
47 * run in linear time (roughly speaking). The constant factor is low compared
48 * to that for the <tt>LinkedList</tt> implementation.<p>
49 *
50 * Each <tt>IdentityArrayList</tt> instance has a <i>capacity</i>. The capacity is
51 * the size of the array used to store the elements in the list. It is always
52 * at least as large as the list size. As elements are added to an IdentityArrayList,
53 * its capacity grows automatically. The details of the growth policy are not
54 * specified beyond the fact that adding an element has constant amortized
55 * time cost.<p>
56 *
57 * An application can increase the capacity of an <tt>IdentityArrayList</tt> instance
58 * before adding a large number of elements using the <tt>ensureCapacity</tt>
59 * operation. This may reduce the amount of incremental reallocation.
60 *
61 * <p><strong>Note that this implementation is not synchronized.</strong>
62 * If multiple threads access an <tt>IdentityArrayList</tt> instance concurrently,
63 * and at least one of the threads modifies the list structurally, it
64 * <i>must</i> be synchronized externally. (A structural modification is
65 * any operation that adds or deletes one or more elements, or explicitly
66 * resizes the backing array; merely setting the value of an element is not
67 * a structural modification.) This is typically accomplished by
68 * synchronizing on some object that naturally encapsulates the list.
69 *
70 * If no such object exists, the list should be "wrapped" using the
71 * {@link Collections#synchronizedList Collections.synchronizedList}
72 * method. This is best done at creation time, to prevent accidental
73 * unsynchronized access to the list:<pre>
74 * List list = Collections.synchronizedList(new IdentityArrayList(...));</pre>
75 *
76 * <p>The iterators returned by this class's <tt>iterator</tt> and
77 * <tt>listIterator</tt> methods are <i>fail-fast</i>: if the list is
78 * structurally modified at any time after the iterator is created, in any way
79 * except through the iterator's own <tt>remove</tt> or <tt>add</tt> methods,
80 * the iterator will throw a {@link ConcurrentModificationException}. Thus, in
81 * the face of concurrent modification, the iterator fails quickly and cleanly,
82 * rather than risking arbitrary, non-deterministic behavior at an undetermined
83 * time in the future.<p>
84 *
85 * Note that the fail-fast behavior of an iterator cannot be guaranteed
86 * as it is, generally speaking, impossible to make any hard guarantees in the
87 * presence of unsynchronized concurrent modification. Fail-fast iterators
88 * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
89 * Therefore, it would be wrong to write a program that depended on this
90 * exception for its correctness: <i>the fail-fast behavior of iterators
91 * should be used only to detect bugs.</i><p>
92 *
93 */
94
95 public class IdentityArrayList<E> extends AbstractList<E>
96 implements List<E>, RandomAccess
97 {
98
99 /**
100 * The array buffer into which the elements of the IdentityArrayList are stored.
101 * The capacity of the IdentityArrayList is the length of this array buffer.
102 */
103 private transient Object[] elementData;
104
105 /**
106 * The size of the IdentityArrayList (the number of elements it contains).
107 *
108 * @serial
109 */
110 private int size;
111
112 /**
113 * Constructs an empty list with the specified initial capacity.
114 *
115 * @param initialCapacity the initial capacity of the list
116 * @exception IllegalArgumentException if the specified initial capacity
117 * is negative
118 */
119 public IdentityArrayList(int initialCapacity) {
120 super();
121 if (initialCapacity < 0)
122 throw new IllegalArgumentException("Illegal Capacity: "+
123 initialCapacity);
124 this.elementData = new Object[initialCapacity];
125 }
126
127 /**
128 * Constructs an empty list with an initial capacity of ten.
129 */
130 public IdentityArrayList() {
131 this(10);
132 }
133
134 /**
135 * Constructs a list containing the elements of the specified
136 * collection, in the order they are returned by the collection's
137 * iterator.
138 *
139 * @param c the collection whose elements are to be placed into this list
140 * @throws NullPointerException if the specified collection is null
141 */
142 public IdentityArrayList(Collection<? extends E> c) {
143 elementData = c.toArray();
144 size = elementData.length;
145 // c.toArray might (incorrectly) not return Object[] (see 6260652)
146 if (elementData.getClass() != Object[].class)
147 elementData = Arrays.copyOf(elementData, size, Object[].class);
148 }
149
150 /**
151 * Trims the capacity of this <tt>IdentityArrayList</tt> instance to be the
152 * list's current size. An application can use this operation to minimize
153 * the storage of an <tt>IdentityArrayList</tt> instance.
154 */
155 public void trimToSize() {
156 modCount++;
157 int oldCapacity = elementData.length;
158 if (size < oldCapacity) {
159 elementData = Arrays.copyOf(elementData, size);
160 }
161 }
162
163 /**
164 * Increases the capacity of this <tt>IdentityArrayList</tt> instance, if
165 * necessary, to ensure that it can hold at least the number of elements
166 * specified by the minimum capacity argument.
167 *
168 * @param minCapacity the desired minimum capacity
169 */
170 public void ensureCapacity(int minCapacity) {
171 modCount++;
172 int oldCapacity = elementData.length;
173 if (minCapacity > oldCapacity) {
174 Object oldData[] = elementData;
175 int newCapacity = (oldCapacity * 3)/2 + 1;
176 if (newCapacity < minCapacity)
177 newCapacity = minCapacity;
178 // minCapacity is usually close to size, so this is a win:
179 elementData = Arrays.copyOf(elementData, newCapacity);
180 }
181 }
182
183 /**
184 * Returns the number of elements in this list.
185 *
186 * @return the number of elements in this list
187 */
188 public int size() {
189 return size;
190 }
191
192 /**
193 * Returns <tt>true</tt> if this list contains no elements.
194 *
195 * @return <tt>true</tt> if this list contains no elements
196 */
197 public boolean isEmpty() {
198 return size == 0;
199 }
200
201 /**
202 * Returns <tt>true</tt> if this list contains the specified element.
203 * More formally, returns <tt>true</tt> if and only if this list contains
204 * at least one element <tt>e</tt> such that
205 * <tt>(o==null ? e==null : o == e)</tt>.
206 *
207 * @param o element whose presence in this list is to be tested
208 * @return <tt>true</tt> if this list contains the specified element
209 */
210 public boolean contains(Object o) {
211 return indexOf(o) >= 0;
212 }
213
214 /**
215 * Returns the index of the first occurrence of the specified element
216 * in this list, or -1 if this list does not contain the element.
217 * More formally, returns the lowest index <tt>i</tt> such that
218 * <tt>(o==null ? get(i)==null : o == get(i))</tt>,
219 * or -1 if there is no such index.
220 */
221 public int indexOf(Object o) {
222 for (int i = 0; i < size; i++) {
223 if (o == elementData[i]) {
224 return i;
225 }
226 }
227 return -1;
228 }
229
230 /**
231 * Returns the index of the last occurrence of the specified element
232 * in this list, or -1 if this list does not contain the element.
233 * More formally, returns the highest index <tt>i</tt> such that
234 * <tt>(o==null ? get(i)==null : o == get(i))</tt>,
235 * or -1 if there is no such index.
236 */
237 public int lastIndexOf(Object o) {
238 for (int i = size-1; i >= 0; i--) {
239 if (o == elementData[i]) {
240 return i;
241 }
242 }
243 return -1;
244 }
245
246 /**
247 * Returns an array containing all of the elements in this list
248 * in proper sequence (from first to last element).
249 *
250 * <p>The returned array will be "safe" in that no references to it are
251 * maintained by this list. (In other words, this method must allocate
252 * a new array). The caller is thus free to modify the returned array.
253 *
254 * <p>This method acts as bridge between array-based and collection-based
255 * APIs.
256 *
257 * @return an array containing all of the elements in this list in
258 * proper sequence
259 */
260 public Object[] toArray() {
261 return Arrays.copyOf(elementData, size);
262 }
263
264 /**
265 * Returns an array containing all of the elements in this list in proper
266 * sequence (from first to last element); the runtime type of the returned
267 * array is that of the specified array. If the list fits in the
268 * specified array, it is returned therein. Otherwise, a new array is
269 * allocated with the runtime type of the specified array and the size of
270 * this list.
271 *
272 * <p>If the list fits in the specified array with room to spare
273 * (i.e., the array has more elements than the list), the element in
274 * the array immediately following the end of the collection is set to
275 * <tt>null</tt>. (This is useful in determining the length of the
276 * list <i>only</i> if the caller knows that the list does not contain
277 * any null elements.)
278 *
279 * @param a the array into which the elements of the list are to
280 * be stored, if it is big enough; otherwise, a new array of the
281 * same runtime type is allocated for this purpose.
282 * @return an array containing the elements of the list
283 * @throws ArrayStoreException if the runtime type of the specified array
284 * is not a supertype of the runtime type of every element in
285 * this list
286 * @throws NullPointerException if the specified array is null
287 */
288 public <T> T[] toArray(T[] a) {
289 if (a.length < size)
290 // Make a new array of a's runtime type, but my contents:
291 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
292 System.arraycopy(elementData, 0, a, 0, size);
293 if (a.length > size)
294 a[size] = null;
295 return a;
296 }
297
298 // Positional Access Operations
299
300 /**
301 * Returns the element at the specified position in this list.
302 *
303 * @param index index of the element to return
304 * @return the element at the specified position in this list
305 * @throws IndexOutOfBoundsException {@inheritDoc}
306 */
307 public E get(int index) {
308 rangeCheck(index);
309
310 return (E) elementData[index];
311 }
312
313 /**
314 * Replaces the element at the specified position in this list with
315 * the specified element.
316 *
317 * @param index index of the element to replace
318 * @param element element to be stored at the specified position
319 * @return the element previously at the specified position
320 * @throws IndexOutOfBoundsException {@inheritDoc}
321 */
322 public E set(int index, E element) {
323 rangeCheck(index);
324
325 E oldValue = (E) elementData[index];
326 elementData[index] = element;
327 return oldValue;
328 }
329
330 /**
331 * Appends the specified element to the end of this list.
332 *
333 * @param e element to be appended to this list
334 * @return <tt>true</tt> (as specified by {@link Collection#add})
335 */
336 public boolean add(E e) {
337 ensureCapacity(size + 1); // Increments modCount!!
338 elementData[size++] = e;
339 return true;
340 }
341
342 /**
343 * Inserts the specified element at the specified position in this
344 * list. Shifts the element currently at that position (if any) and
345 * any subsequent elements to the right (adds one to their indices).
346 *
347 * @param index index at which the specified element is to be inserted
348 * @param element element to be inserted
349 * @throws IndexOutOfBoundsException {@inheritDoc}
350 */
351 public void add(int index, E element) {
352 rangeCheckForAdd(index);
353
354 ensureCapacity(size+1); // Increments modCount!!
355 System.arraycopy(elementData, index, elementData, index + 1,
356 size - index);
357 elementData[index] = element;
358 size++;
359 }
360
361 /**
362 * Removes the element at the specified position in this list.
363 * Shifts any subsequent elements to the left (subtracts one from their
364 * indices).
365 *
366 * @param index the index of the element to be removed
367 * @return the element that was removed from the list
368 * @throws IndexOutOfBoundsException {@inheritDoc}
369 */
370 public E remove(int index) {
371 rangeCheck(index);
372
373 modCount++;
374 E oldValue = (E) elementData[index];
375
376 int numMoved = size - index - 1;
377 if (numMoved > 0)
378 System.arraycopy(elementData, index+1, elementData, index,
379 numMoved);
380 elementData[--size] = null; // Let gc do its work
381
382 return oldValue;
383 }
384
385 /**
386 * Removes the first occurrence of the specified element from this list,
387 * if it is present. If the list does not contain the element, it is
388 * unchanged. More formally, removes the element with the lowest index
389 * <tt>i</tt> such that
390 * <tt>(o==null ? get(i)==null : o == get(i))</tt>
391 * (if such an element exists). Returns <tt>true</tt> if this list
392 * contained the specified element (or equivalently, if this list
393 * changed as a result of the call).
394 *
395 * @param o element to be removed from this list, if present
396 * @return <tt>true</tt> if this list contained the specified element
397 */
398 public boolean remove(Object o) {
399 for (int index = 0; index < size; index++) {
400 if (o == elementData[index]) {
401 fastRemove(index);
402 return true;
403 }
404 }
405 return false;
406 }
407
408 /*
409 * Private remove method that skips bounds checking and does not
410 * return the value removed.
411 */
412 private void fastRemove(int index) {
413 modCount++;
414 int numMoved = size - index - 1;
415 if (numMoved > 0)
416 System.arraycopy(elementData, index+1, elementData, index,
417 numMoved);
418 elementData[--size] = null; // Let gc do its work
419 }
420
421 /**
422 * Removes all of the elements from this list. The list will
423 * be empty after this call returns.
424 */
425 public void clear() {
426 modCount++;
427
428 // Let gc do its work
429 for (int i = 0; i < size; i++)
430 elementData[i] = null;
431
432 size = 0;
433 }
434
435 /**
436 * Appends all of the elements in the specified collection to the end of
437 * this list, in the order that they are returned by the
438 * specified collection's Iterator. The behavior of this operation is
439 * undefined if the specified collection is modified while the operation
440 * is in progress. (This implies that the behavior of this call is
441 * undefined if the specified collection is this list, and this
442 * list is nonempty.)
443 *
444 * @param c collection containing elements to be added to this list
445 * @return <tt>true</tt> if this list changed as a result of the call
446 * @throws NullPointerException if the specified collection is null
447 */
448 public boolean addAll(Collection<? extends E> c) {
449 Object[] a = c.toArray();
450 int numNew = a.length;
451 ensureCapacity(size + numNew); // Increments modCount
452 System.arraycopy(a, 0, elementData, size, numNew);
453 size += numNew;
454 return numNew != 0;
455 }
456
457 /**
458 * Inserts all of the elements in the specified collection into this
459 * list, starting at the specified position. Shifts the element
460 * currently at that position (if any) and any subsequent elements to
461 * the right (increases their indices). The new elements will appear
462 * in the list in the order that they are returned by the
463 * specified collection's iterator.
464 *
465 * @param index index at which to insert the first element from the
466 * specified collection
467 * @param c collection containing elements to be added to this list
468 * @return <tt>true</tt> if this list changed as a result of the call
469 * @throws IndexOutOfBoundsException {@inheritDoc}
470 * @throws NullPointerException if the specified collection is null
471 */
472 public boolean addAll(int index, Collection<? extends E> c) {
473 rangeCheckForAdd(index);
474
475 Object[] a = c.toArray();
476 int numNew = a.length;
477 ensureCapacity(size + numNew); // Increments modCount
478
479 int numMoved = size - index;
480 if (numMoved > 0) {
481 System.arraycopy(elementData, index, elementData, index + numNew, numMoved);
482 }
483
484 System.arraycopy(a, 0, elementData, index, numNew);
485 size += numNew;
486 return numNew != 0;
487 }
488
489 /**
490 * Removes from this list all of the elements whose index is between
491 * <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive.
492 * Shifts any succeeding elements to the left (reduces their index).
493 * This call shortens the list by <tt>(toIndex - fromIndex)</tt> elements.
494 * (If <tt>toIndex==fromIndex</tt>, this operation has no effect.)
495 *
496 * @param fromIndex index of first element to be removed
497 * @param toIndex index after last element to be removed
498 * @throws IndexOutOfBoundsException if fromIndex or toIndex out of
499 * range (fromIndex < 0 || fromIndex >= size() || toIndex
500 * > size() || toIndex < fromIndex)
501 */
502 protected void removeRange(int fromIndex, int toIndex) {
503 modCount++;
504 int numMoved = size - toIndex;
505 System.arraycopy(elementData, toIndex, elementData, fromIndex,
506 numMoved);
507
508 // Let gc do its work
509 int newSize = size - (toIndex-fromIndex);
510 while (size != newSize)
511 elementData[--size] = null;
512 }
513
514 /**
515 * Checks if the given index is in range. If not, throws an appropriate
516 * runtime exception. This method does *not* check if the index is
517 * negative: It is always used immediately prior to an array access,
518 * which throws an ArrayIndexOutOfBoundsException if index is negative.
519 */
520 private void rangeCheck(int index) {
521 if (index >= size)
522 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
523 }
524
525 /**
526 * A version of rangeCheck used by add and addAll.
527 */
528 private void rangeCheckForAdd(int index) {
529 if (index > size || index < 0)
530 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
531 }
532
533 /**
534 * Constructs an IndexOutOfBoundsException detail message.
535 * Of the many possible refactorings of the error handling code,
536 * this "outlining" performs best with both server and client VMs.
537 */
538 private String outOfBoundsMsg(int index) {
539 return "Index: "+index+", Size: "+size;
540 }
541 }