rev 17661 : 8177290: add copy factory methods for unmodifiable List, Set, Map
8184690: add Collectors for collecting into unmodifiable List, Set, and Map
Reviewed-by: XXX

   1 /*
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   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
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   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
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  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 java.util;
  27 
  28 import java.util.function.UnaryOperator;
  29 
  30 /**
  31  * An ordered collection (also known as a <i>sequence</i>).  The user of this
  32  * interface has precise control over where in the list each element is
  33  * inserted.  The user can access elements by their integer index (position in
  34  * the list), and search for elements in the list.<p>
  35  *
  36  * Unlike sets, lists typically allow duplicate elements.  More formally,
  37  * lists typically allow pairs of elements {@code e1} and {@code e2}
  38  * such that {@code e1.equals(e2)}, and they typically allow multiple
  39  * null elements if they allow null elements at all.  It is not inconceivable
  40  * that someone might wish to implement a list that prohibits duplicates, by
  41  * throwing runtime exceptions when the user attempts to insert them, but we
  42  * expect this usage to be rare.<p>
  43  *
  44  * The {@code List} interface places additional stipulations, beyond those
  45  * specified in the {@code Collection} interface, on the contracts of the
  46  * {@code iterator}, {@code add}, {@code remove}, {@code equals}, and
  47  * {@code hashCode} methods.  Declarations for other inherited methods are
  48  * also included here for convenience.<p>
  49  *
  50  * The {@code List} interface provides four methods for positional (indexed)
  51  * access to list elements.  Lists (like Java arrays) are zero based.  Note
  52  * that these operations may execute in time proportional to the index value
  53  * for some implementations (the {@code LinkedList} class, for
  54  * example). Thus, iterating over the elements in a list is typically
  55  * preferable to indexing through it if the caller does not know the
  56  * implementation.<p>
  57  *
  58  * The {@code List} interface provides a special iterator, called a
  59  * {@code ListIterator}, that allows element insertion and replacement, and
  60  * bidirectional access in addition to the normal operations that the
  61  * {@code Iterator} interface provides.  A method is provided to obtain a
  62  * list iterator that starts at a specified position in the list.<p>
  63  *
  64  * The {@code List} interface provides two methods to search for a specified
  65  * object.  From a performance standpoint, these methods should be used with
  66  * caution.  In many implementations they will perform costly linear
  67  * searches.<p>
  68  *
  69  * The {@code List} interface provides two methods to efficiently insert and
  70  * remove multiple elements at an arbitrary point in the list.<p>
  71  *
  72  * Note: While it is permissible for lists to contain themselves as elements,
  73  * extreme caution is advised: the {@code equals} and {@code hashCode}
  74  * methods are no longer well defined on such a list.
  75  *
  76  * <p>Some list implementations have restrictions on the elements that
  77  * they may contain.  For example, some implementations prohibit null elements,
  78  * and some have restrictions on the types of their elements.  Attempting to
  79  * add an ineligible element throws an unchecked exception, typically
  80  * {@code NullPointerException} or {@code ClassCastException}.  Attempting
  81  * to query the presence of an ineligible element may throw an exception,
  82  * or it may simply return false; some implementations will exhibit the former
  83  * behavior and some will exhibit the latter.  More generally, attempting an
  84  * operation on an ineligible element whose completion would not result in
  85  * the insertion of an ineligible element into the list may throw an
  86  * exception or it may succeed, at the option of the implementation.
  87  * Such exceptions are marked as "optional" in the specification for this
  88  * interface.
  89  *
  90  * <h2><a id="unmodifiable">Unmodifiable Lists</a></h2>
  91  * <p>The {@link List#of(Object...) List.of} and
  92  * {@link List#copyOf List.copyOf} static factory methods
  93  * provide a convenient way to create unmodifiable lists. The {@code List}
  94  * instances created by these methods have the following characteristics:
  95  *
  96  * <ul>
  97  * <li>They are <a href="Collection.html#unmodifiable"><i>unmodifiable</i></a>. Elements cannot
  98  * be added, removed, or replaced. Calling any mutator method on the List
  99  * will always cause {@code UnsupportedOperationException} to be thrown.
 100  * However, if the contained elements are themselves mutable,
 101  * this may cause the List's contents to appear to change.
 102  * <li>They disallow {@code null} elements. Attempts to create them with
 103  * {@code null} elements result in {@code NullPointerException}.
 104  * <li>They are serializable if all elements are serializable.
 105  * <li>The order of elements in the list is the same as the order of the
 106  * provided arguments, or of the elements in the provided array.
 107  * <li>They are <a href="../lang/doc-files/ValueBased.html">value-based</a>.
 108  * Callers should make no assumptions about the identity of the returned instances.
 109  * Factories are free to create new instances or reuse existing ones. Therefore,
 110  * identity-sensitive operations on these instances (reference equality ({@code ==}),
 111  * identity hash code, and synchronization) are unreliable and should be avoided.
 112  * <li>They are serialized as specified on the
 113  * <a href="{@docRoot}/serialized-form.html#java.util.CollSer">Serialized Form</a>
 114  * page.
 115  * </ul>
 116  *
 117  * <p>This interface is a member of the
 118  * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
 119  * Java Collections Framework</a>.
 120  *
 121  * @param <E> the type of elements in this list
 122  *
 123  * @author  Josh Bloch
 124  * @author  Neal Gafter
 125  * @see Collection
 126  * @see Set
 127  * @see ArrayList
 128  * @see LinkedList
 129  * @see Vector
 130  * @see Arrays#asList(Object[])
 131  * @see Collections#nCopies(int, Object)
 132  * @see Collections#EMPTY_LIST
 133  * @see AbstractList
 134  * @see AbstractSequentialList
 135  * @since 1.2
 136  */
 137 
 138 public interface List<E> extends Collection<E> {
 139     // Query Operations
 140 
 141     /**
 142      * Returns the number of elements in this list.  If this list contains
 143      * more than {@code Integer.MAX_VALUE} elements, returns
 144      * {@code Integer.MAX_VALUE}.
 145      *
 146      * @return the number of elements in this list
 147      */
 148     int size();
 149 
 150     /**
 151      * Returns {@code true} if this list contains no elements.
 152      *
 153      * @return {@code true} if this list contains no elements
 154      */
 155     boolean isEmpty();
 156 
 157     /**
 158      * Returns {@code true} if this list contains the specified element.
 159      * More formally, returns {@code true} if and only if this list contains
 160      * at least one element {@code e} such that
 161      * {@code Objects.equals(o, e)}.
 162      *
 163      * @param o element whose presence in this list is to be tested
 164      * @return {@code true} if this list contains the specified element
 165      * @throws ClassCastException if the type of the specified element
 166      *         is incompatible with this list
 167      * (<a href="Collection.html#optional-restrictions">optional</a>)
 168      * @throws NullPointerException if the specified element is null and this
 169      *         list does not permit null elements
 170      * (<a href="Collection.html#optional-restrictions">optional</a>)
 171      */
 172     boolean contains(Object o);
 173 
 174     /**
 175      * Returns an iterator over the elements in this list in proper sequence.
 176      *
 177      * @return an iterator over the elements in this list in proper sequence
 178      */
 179     Iterator<E> iterator();
 180 
 181     /**
 182      * Returns an array containing all of the elements in this list in proper
 183      * sequence (from first to last element).
 184      *
 185      * <p>The returned array will be "safe" in that no references to it are
 186      * maintained by this list.  (In other words, this method must
 187      * allocate a new array even if this list is backed by an array).
 188      * The caller is thus free to modify the returned array.
 189      *
 190      * <p>This method acts as bridge between array-based and collection-based
 191      * APIs.
 192      *
 193      * @return an array containing all of the elements in this list in proper
 194      *         sequence
 195      * @see Arrays#asList(Object[])
 196      */
 197     Object[] toArray();
 198 
 199     /**
 200      * Returns an array containing all of the elements in this list in
 201      * proper sequence (from first to last element); the runtime type of
 202      * the returned array is that of the specified array.  If the list fits
 203      * in the specified array, it is returned therein.  Otherwise, a new
 204      * array is allocated with the runtime type of the specified array and
 205      * the size of this list.
 206      *
 207      * <p>If the list fits in the specified array with room to spare (i.e.,
 208      * the array has more elements than the list), the element in the array
 209      * immediately following the end of the list is set to {@code null}.
 210      * (This is useful in determining the length of the list <i>only</i> if
 211      * the caller knows that the list does not contain any null elements.)
 212      *
 213      * <p>Like the {@link #toArray()} method, this method acts as bridge between
 214      * array-based and collection-based APIs.  Further, this method allows
 215      * precise control over the runtime type of the output array, and may,
 216      * under certain circumstances, be used to save allocation costs.
 217      *
 218      * <p>Suppose {@code x} is a list known to contain only strings.
 219      * The following code can be used to dump the list into a newly
 220      * allocated array of {@code String}:
 221      *
 222      * <pre>{@code
 223      *     String[] y = x.toArray(new String[0]);
 224      * }</pre>
 225      *
 226      * Note that {@code toArray(new Object[0])} is identical in function to
 227      * {@code toArray()}.
 228      *
 229      * @param a the array into which the elements of this list are to
 230      *          be stored, if it is big enough; otherwise, a new array of the
 231      *          same runtime type is allocated for this purpose.
 232      * @return an array containing the elements of this list
 233      * @throws ArrayStoreException if the runtime type of the specified array
 234      *         is not a supertype of the runtime type of every element in
 235      *         this list
 236      * @throws NullPointerException if the specified array is null
 237      */
 238     <T> T[] toArray(T[] a);
 239 
 240 
 241     // Modification Operations
 242 
 243     /**
 244      * Appends the specified element to the end of this list (optional
 245      * operation).
 246      *
 247      * <p>Lists that support this operation may place limitations on what
 248      * elements may be added to this list.  In particular, some
 249      * lists will refuse to add null elements, and others will impose
 250      * restrictions on the type of elements that may be added.  List
 251      * classes should clearly specify in their documentation any restrictions
 252      * on what elements may be added.
 253      *
 254      * @param e element to be appended to this list
 255      * @return {@code true} (as specified by {@link Collection#add})
 256      * @throws UnsupportedOperationException if the {@code add} operation
 257      *         is not supported by this list
 258      * @throws ClassCastException if the class of the specified element
 259      *         prevents it from being added to this list
 260      * @throws NullPointerException if the specified element is null and this
 261      *         list does not permit null elements
 262      * @throws IllegalArgumentException if some property of this element
 263      *         prevents it from being added to this list
 264      */
 265     boolean add(E e);
 266 
 267     /**
 268      * Removes the first occurrence of the specified element from this list,
 269      * if it is present (optional operation).  If this list does not contain
 270      * the element, it is unchanged.  More formally, removes the element with
 271      * the lowest index {@code i} such that
 272      * {@code Objects.equals(o, get(i))}
 273      * (if such an element exists).  Returns {@code true} if this list
 274      * contained the specified element (or equivalently, if this list changed
 275      * as a result of the call).
 276      *
 277      * @param o element to be removed from this list, if present
 278      * @return {@code true} if this list contained the specified element
 279      * @throws ClassCastException if the type of the specified element
 280      *         is incompatible with this list
 281      * (<a href="Collection.html#optional-restrictions">optional</a>)
 282      * @throws NullPointerException if the specified element is null and this
 283      *         list does not permit null elements
 284      * (<a href="Collection.html#optional-restrictions">optional</a>)
 285      * @throws UnsupportedOperationException if the {@code remove} operation
 286      *         is not supported by this list
 287      */
 288     boolean remove(Object o);
 289 
 290 
 291     // Bulk Modification Operations
 292 
 293     /**
 294      * Returns {@code true} if this list contains all of the elements of the
 295      * specified collection.
 296      *
 297      * @param  c collection to be checked for containment in this list
 298      * @return {@code true} if this list contains all of the elements of the
 299      *         specified collection
 300      * @throws ClassCastException if the types of one or more elements
 301      *         in the specified collection are incompatible with this
 302      *         list
 303      * (<a href="Collection.html#optional-restrictions">optional</a>)
 304      * @throws NullPointerException if the specified collection contains one
 305      *         or more null elements and this list does not permit null
 306      *         elements
 307      *         (<a href="Collection.html#optional-restrictions">optional</a>),
 308      *         or if the specified collection is null
 309      * @see #contains(Object)
 310      */
 311     boolean containsAll(Collection<?> c);
 312 
 313     /**
 314      * Appends all of the elements in the specified collection to the end of
 315      * this list, in the order that they are returned by the specified
 316      * collection's iterator (optional operation).  The behavior of this
 317      * operation is undefined if the specified collection is modified while
 318      * the operation is in progress.  (Note that this will occur if the
 319      * specified collection is this list, and it's nonempty.)
 320      *
 321      * @param c collection containing elements to be added to this list
 322      * @return {@code true} if this list changed as a result of the call
 323      * @throws UnsupportedOperationException if the {@code addAll} operation
 324      *         is not supported by this list
 325      * @throws ClassCastException if the class of an element of the specified
 326      *         collection prevents it from being added to this list
 327      * @throws NullPointerException if the specified collection contains one
 328      *         or more null elements and this list does not permit null
 329      *         elements, or if the specified collection is null
 330      * @throws IllegalArgumentException if some property of an element of the
 331      *         specified collection prevents it from being added to this list
 332      * @see #add(Object)
 333      */
 334     boolean addAll(Collection<? extends E> c);
 335 
 336     /**
 337      * Inserts all of the elements in the specified collection into this
 338      * list at the specified position (optional operation).  Shifts the
 339      * element currently at that position (if any) and any subsequent
 340      * elements to the right (increases their indices).  The new elements
 341      * will appear in this list in the order that they are returned by the
 342      * specified collection's iterator.  The behavior of this operation is
 343      * undefined if the specified collection is modified while the
 344      * operation is in progress.  (Note that this will occur if the specified
 345      * collection is this list, and it's nonempty.)
 346      *
 347      * @param index index at which to insert the first element from the
 348      *              specified collection
 349      * @param c collection containing elements to be added to this list
 350      * @return {@code true} if this list changed as a result of the call
 351      * @throws UnsupportedOperationException if the {@code addAll} operation
 352      *         is not supported by this list
 353      * @throws ClassCastException if the class of an element of the specified
 354      *         collection prevents it from being added to this list
 355      * @throws NullPointerException if the specified collection contains one
 356      *         or more null elements and this list does not permit null
 357      *         elements, or if the specified collection is null
 358      * @throws IllegalArgumentException if some property of an element of the
 359      *         specified collection prevents it from being added to this list
 360      * @throws IndexOutOfBoundsException if the index is out of range
 361      *         ({@code index < 0 || index > size()})
 362      */
 363     boolean addAll(int index, Collection<? extends E> c);
 364 
 365     /**
 366      * Removes from this list all of its elements that are contained in the
 367      * specified collection (optional operation).
 368      *
 369      * @param c collection containing elements to be removed from this list
 370      * @return {@code true} if this list changed as a result of the call
 371      * @throws UnsupportedOperationException if the {@code removeAll} operation
 372      *         is not supported by this list
 373      * @throws ClassCastException if the class of an element of this list
 374      *         is incompatible with the specified collection
 375      * (<a href="Collection.html#optional-restrictions">optional</a>)
 376      * @throws NullPointerException if this list contains a null element and the
 377      *         specified collection does not permit null elements
 378      *         (<a href="Collection.html#optional-restrictions">optional</a>),
 379      *         or if the specified collection is null
 380      * @see #remove(Object)
 381      * @see #contains(Object)
 382      */
 383     boolean removeAll(Collection<?> c);
 384 
 385     /**
 386      * Retains only the elements in this list that are contained in the
 387      * specified collection (optional operation).  In other words, removes
 388      * from this list all of its elements that are not contained in the
 389      * specified collection.
 390      *
 391      * @param c collection containing elements to be retained in this list
 392      * @return {@code true} if this list changed as a result of the call
 393      * @throws UnsupportedOperationException if the {@code retainAll} operation
 394      *         is not supported by this list
 395      * @throws ClassCastException if the class of an element of this list
 396      *         is incompatible with the specified collection
 397      * (<a href="Collection.html#optional-restrictions">optional</a>)
 398      * @throws NullPointerException if this list contains a null element and the
 399      *         specified collection does not permit null elements
 400      *         (<a href="Collection.html#optional-restrictions">optional</a>),
 401      *         or if the specified collection is null
 402      * @see #remove(Object)
 403      * @see #contains(Object)
 404      */
 405     boolean retainAll(Collection<?> c);
 406 
 407     /**
 408      * Replaces each element of this list with the result of applying the
 409      * operator to that element.  Errors or runtime exceptions thrown by
 410      * the operator are relayed to the caller.
 411      *
 412      * @implSpec
 413      * The default implementation is equivalent to, for this {@code list}:
 414      * <pre>{@code
 415      *     final ListIterator<E> li = list.listIterator();
 416      *     while (li.hasNext()) {
 417      *         li.set(operator.apply(li.next()));
 418      *     }
 419      * }</pre>
 420      *
 421      * If the list's list-iterator does not support the {@code set} operation
 422      * then an {@code UnsupportedOperationException} will be thrown when
 423      * replacing the first element.
 424      *
 425      * @param operator the operator to apply to each element
 426      * @throws UnsupportedOperationException if this list is unmodifiable.
 427      *         Implementations may throw this exception if an element
 428      *         cannot be replaced or if, in general, modification is not
 429      *         supported
 430      * @throws NullPointerException if the specified operator is null or
 431      *         if the operator result is a null value and this list does
 432      *         not permit null elements
 433      *         (<a href="Collection.html#optional-restrictions">optional</a>)
 434      * @since 1.8
 435      */
 436     default void replaceAll(UnaryOperator<E> operator) {
 437         Objects.requireNonNull(operator);
 438         final ListIterator<E> li = this.listIterator();
 439         while (li.hasNext()) {
 440             li.set(operator.apply(li.next()));
 441         }
 442     }
 443 
 444     /**
 445      * Sorts this list according to the order induced by the specified
 446      * {@link Comparator}.
 447      *
 448      * <p>All elements in this list must be <i>mutually comparable</i> using the
 449      * specified comparator (that is, {@code c.compare(e1, e2)} must not throw
 450      * a {@code ClassCastException} for any elements {@code e1} and {@code e2}
 451      * in the list).
 452      *
 453      * <p>If the specified comparator is {@code null} then all elements in this
 454      * list must implement the {@link Comparable} interface and the elements'
 455      * {@linkplain Comparable natural ordering} should be used.
 456      *
 457      * <p>This list must be modifiable, but need not be resizable.
 458      *
 459      * @implSpec
 460      * The default implementation obtains an array containing all elements in
 461      * this list, sorts the array, and iterates over this list resetting each
 462      * element from the corresponding position in the array. (This avoids the
 463      * n<sup>2</sup> log(n) performance that would result from attempting
 464      * to sort a linked list in place.)
 465      *
 466      * @implNote
 467      * This implementation is a stable, adaptive, iterative mergesort that
 468      * requires far fewer than n lg(n) comparisons when the input array is
 469      * partially sorted, while offering the performance of a traditional
 470      * mergesort when the input array is randomly ordered.  If the input array
 471      * is nearly sorted, the implementation requires approximately n
 472      * comparisons.  Temporary storage requirements vary from a small constant
 473      * for nearly sorted input arrays to n/2 object references for randomly
 474      * ordered input arrays.
 475      *
 476      * <p>The implementation takes equal advantage of ascending and
 477      * descending order in its input array, and can take advantage of
 478      * ascending and descending order in different parts of the same
 479      * input array.  It is well-suited to merging two or more sorted arrays:
 480      * simply concatenate the arrays and sort the resulting array.
 481      *
 482      * <p>The implementation was adapted from Tim Peters's list sort for Python
 483      * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
 484      * TimSort</a>).  It uses techniques from Peter McIlroy's "Optimistic
 485      * Sorting and Information Theoretic Complexity", in Proceedings of the
 486      * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
 487      * January 1993.
 488      *
 489      * @param c the {@code Comparator} used to compare list elements.
 490      *          A {@code null} value indicates that the elements'
 491      *          {@linkplain Comparable natural ordering} should be used
 492      * @throws ClassCastException if the list contains elements that are not
 493      *         <i>mutually comparable</i> using the specified comparator
 494      * @throws UnsupportedOperationException if the list's list-iterator does
 495      *         not support the {@code set} operation
 496      * @throws IllegalArgumentException
 497      *         (<a href="Collection.html#optional-restrictions">optional</a>)
 498      *         if the comparator is found to violate the {@link Comparator}
 499      *         contract
 500      * @since 1.8
 501      */
 502     @SuppressWarnings({"unchecked", "rawtypes"})
 503     default void sort(Comparator<? super E> c) {
 504         Object[] a = this.toArray();
 505         Arrays.sort(a, (Comparator) c);
 506         ListIterator<E> i = this.listIterator();
 507         for (Object e : a) {
 508             i.next();
 509             i.set((E) e);
 510         }
 511     }
 512 
 513     /**
 514      * Removes all of the elements from this list (optional operation).
 515      * The list will be empty after this call returns.
 516      *
 517      * @throws UnsupportedOperationException if the {@code clear} operation
 518      *         is not supported by this list
 519      */
 520     void clear();
 521 
 522 
 523     // Comparison and hashing
 524 
 525     /**
 526      * Compares the specified object with this list for equality.  Returns
 527      * {@code true} if and only if the specified object is also a list, both
 528      * lists have the same size, and all corresponding pairs of elements in
 529      * the two lists are <i>equal</i>.  (Two elements {@code e1} and
 530      * {@code e2} are <i>equal</i> if {@code Objects.equals(e1, e2)}.)
 531      * In other words, two lists are defined to be
 532      * equal if they contain the same elements in the same order.  This
 533      * definition ensures that the equals method works properly across
 534      * different implementations of the {@code List} interface.
 535      *
 536      * @param o the object to be compared for equality with this list
 537      * @return {@code true} if the specified object is equal to this list
 538      */
 539     boolean equals(Object o);
 540 
 541     /**
 542      * Returns the hash code value for this list.  The hash code of a list
 543      * is defined to be the result of the following calculation:
 544      * <pre>{@code
 545      *     int hashCode = 1;
 546      *     for (E e : list)
 547      *         hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
 548      * }</pre>
 549      * This ensures that {@code list1.equals(list2)} implies that
 550      * {@code list1.hashCode()==list2.hashCode()} for any two lists,
 551      * {@code list1} and {@code list2}, as required by the general
 552      * contract of {@link Object#hashCode}.
 553      *
 554      * @return the hash code value for this list
 555      * @see Object#equals(Object)
 556      * @see #equals(Object)
 557      */
 558     int hashCode();
 559 
 560 
 561     // Positional Access Operations
 562 
 563     /**
 564      * Returns the element at the specified position in this list.
 565      *
 566      * @param index index of the element to return
 567      * @return the element at the specified position in this list
 568      * @throws IndexOutOfBoundsException if the index is out of range
 569      *         ({@code index < 0 || index >= size()})
 570      */
 571     E get(int index);
 572 
 573     /**
 574      * Replaces the element at the specified position in this list with the
 575      * specified element (optional operation).
 576      *
 577      * @param index index of the element to replace
 578      * @param element element to be stored at the specified position
 579      * @return the element previously at the specified position
 580      * @throws UnsupportedOperationException if the {@code set} operation
 581      *         is not supported by this list
 582      * @throws ClassCastException if the class of the specified element
 583      *         prevents it from being added to this list
 584      * @throws NullPointerException if the specified element is null and
 585      *         this list does not permit null elements
 586      * @throws IllegalArgumentException if some property of the specified
 587      *         element prevents it from being added to this list
 588      * @throws IndexOutOfBoundsException if the index is out of range
 589      *         ({@code index < 0 || index >= size()})
 590      */
 591     E set(int index, E element);
 592 
 593     /**
 594      * Inserts the specified element at the specified position in this list
 595      * (optional operation).  Shifts the element currently at that position
 596      * (if any) and any subsequent elements to the right (adds one to their
 597      * indices).
 598      *
 599      * @param index index at which the specified element is to be inserted
 600      * @param element element to be inserted
 601      * @throws UnsupportedOperationException if the {@code add} operation
 602      *         is not supported by this list
 603      * @throws ClassCastException if the class of the specified element
 604      *         prevents it from being added to this list
 605      * @throws NullPointerException if the specified element is null and
 606      *         this list does not permit null elements
 607      * @throws IllegalArgumentException if some property of the specified
 608      *         element prevents it from being added to this list
 609      * @throws IndexOutOfBoundsException if the index is out of range
 610      *         ({@code index < 0 || index > size()})
 611      */
 612     void add(int index, E element);
 613 
 614     /**
 615      * Removes the element at the specified position in this list (optional
 616      * operation).  Shifts any subsequent elements to the left (subtracts one
 617      * from their indices).  Returns the element that was removed from the
 618      * list.
 619      *
 620      * @param index the index of the element to be removed
 621      * @return the element previously at the specified position
 622      * @throws UnsupportedOperationException if the {@code remove} operation
 623      *         is not supported by this list
 624      * @throws IndexOutOfBoundsException if the index is out of range
 625      *         ({@code index < 0 || index >= size()})
 626      */
 627     E remove(int index);
 628 
 629 
 630     // Search Operations
 631 
 632     /**
 633      * Returns the index of the first occurrence of the specified element
 634      * in this list, or -1 if this list does not contain the element.
 635      * More formally, returns the lowest index {@code i} such that
 636      * {@code Objects.equals(o, get(i))},
 637      * or -1 if there is no such index.
 638      *
 639      * @param o element to search for
 640      * @return the index of the first occurrence of the specified element in
 641      *         this list, or -1 if this list does not contain the element
 642      * @throws ClassCastException if the type of the specified element
 643      *         is incompatible with this list
 644      *         (<a href="Collection.html#optional-restrictions">optional</a>)
 645      * @throws NullPointerException if the specified element is null and this
 646      *         list does not permit null elements
 647      *         (<a href="Collection.html#optional-restrictions">optional</a>)
 648      */
 649     int indexOf(Object o);
 650 
 651     /**
 652      * Returns the index of the last occurrence of the specified element
 653      * in this list, or -1 if this list does not contain the element.
 654      * More formally, returns the highest index {@code i} such that
 655      * {@code Objects.equals(o, get(i))},
 656      * or -1 if there is no such index.
 657      *
 658      * @param o element to search for
 659      * @return the index of the last occurrence of the specified element in
 660      *         this list, or -1 if this list does not contain the element
 661      * @throws ClassCastException if the type of the specified element
 662      *         is incompatible with this list
 663      *         (<a href="Collection.html#optional-restrictions">optional</a>)
 664      * @throws NullPointerException if the specified element is null and this
 665      *         list does not permit null elements
 666      *         (<a href="Collection.html#optional-restrictions">optional</a>)
 667      */
 668     int lastIndexOf(Object o);
 669 
 670 
 671     // List Iterators
 672 
 673     /**
 674      * Returns a list iterator over the elements in this list (in proper
 675      * sequence).
 676      *
 677      * @return a list iterator over the elements in this list (in proper
 678      *         sequence)
 679      */
 680     ListIterator<E> listIterator();
 681 
 682     /**
 683      * Returns a list iterator over the elements in this list (in proper
 684      * sequence), starting at the specified position in the list.
 685      * The specified index indicates the first element that would be
 686      * returned by an initial call to {@link ListIterator#next next}.
 687      * An initial call to {@link ListIterator#previous previous} would
 688      * return the element with the specified index minus one.
 689      *
 690      * @param index index of the first element to be returned from the
 691      *        list iterator (by a call to {@link ListIterator#next next})
 692      * @return a list iterator over the elements in this list (in proper
 693      *         sequence), starting at the specified position in the list
 694      * @throws IndexOutOfBoundsException if the index is out of range
 695      *         ({@code index < 0 || index > size()})
 696      */
 697     ListIterator<E> listIterator(int index);
 698 
 699     // View
 700 
 701     /**
 702      * Returns a view of the portion of this list between the specified
 703      * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.  (If
 704      * {@code fromIndex} and {@code toIndex} are equal, the returned list is
 705      * empty.)  The returned list is backed by this list, so non-structural
 706      * changes in the returned list are reflected in this list, and vice-versa.
 707      * The returned list supports all of the optional list operations supported
 708      * by this list.<p>
 709      *
 710      * This method eliminates the need for explicit range operations (of
 711      * the sort that commonly exist for arrays).  Any operation that expects
 712      * a list can be used as a range operation by passing a subList view
 713      * instead of a whole list.  For example, the following idiom
 714      * removes a range of elements from a list:
 715      * <pre>{@code
 716      *      list.subList(from, to).clear();
 717      * }</pre>
 718      * Similar idioms may be constructed for {@code indexOf} and
 719      * {@code lastIndexOf}, and all of the algorithms in the
 720      * {@code Collections} class can be applied to a subList.<p>
 721      *
 722      * The semantics of the list returned by this method become undefined if
 723      * the backing list (i.e., this list) is <i>structurally modified</i> in
 724      * any way other than via the returned list.  (Structural modifications are
 725      * those that change the size of this list, or otherwise perturb it in such
 726      * a fashion that iterations in progress may yield incorrect results.)
 727      *
 728      * @param fromIndex low endpoint (inclusive) of the subList
 729      * @param toIndex high endpoint (exclusive) of the subList
 730      * @return a view of the specified range within this list
 731      * @throws IndexOutOfBoundsException for an illegal endpoint index value
 732      *         ({@code fromIndex < 0 || toIndex > size ||
 733      *         fromIndex > toIndex})
 734      */
 735     List<E> subList(int fromIndex, int toIndex);
 736 
 737     /**
 738      * Creates a {@link Spliterator} over the elements in this list.
 739      *
 740      * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
 741      * {@link Spliterator#ORDERED}.  Implementations should document the
 742      * reporting of additional characteristic values.
 743      *
 744      * @implSpec
 745      * The default implementation creates a
 746      * <em><a href="Spliterator.html#binding">late-binding</a></em>
 747      * spliterator as follows:
 748      * <ul>
 749      * <li>If the list is an instance of {@link RandomAccess} then the default
 750      *     implementation creates a spliterator that traverses elements by
 751      *     invoking the method {@link List#get}.  If such invocation results or
 752      *     would result in an {@code IndexOutOfBoundsException} then the
 753      *     spliterator will <em>fail-fast</em> and throw a
 754      *     {@code ConcurrentModificationException}.
 755      *     If the list is also an instance of {@link AbstractList} then the
 756      *     spliterator will use the list's {@link AbstractList#modCount modCount}
 757      *     field to provide additional <em>fail-fast</em> behavior.
 758      * <li>Otherwise, the default implementation creates a spliterator from the
 759      *     list's {@code Iterator}.  The spliterator inherits the
 760      *     <em>fail-fast</em> of the list's iterator.
 761      * </ul>
 762      *
 763      * @implNote
 764      * The created {@code Spliterator} additionally reports
 765      * {@link Spliterator#SUBSIZED}.
 766      *
 767      * @return a {@code Spliterator} over the elements in this list
 768      * @since 1.8
 769      */
 770     @Override
 771     default Spliterator<E> spliterator() {
 772         if (this instanceof RandomAccess) {
 773             return new AbstractList.RandomAccessSpliterator<>(this);
 774         } else {
 775             return Spliterators.spliterator(this, Spliterator.ORDERED);
 776         }
 777     }
 778 
 779     /**
 780      * Returns an unmodifiable list containing zero elements.
 781      *
 782      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 783      *
 784      * @param <E> the {@code List}'s element type
 785      * @return an empty {@code List}
 786      *
 787      * @since 9
 788      */
 789     static <E> List<E> of() {
 790         return ImmutableCollections.List0.instance();
 791     }
 792 
 793     /**
 794      * Returns an unmodifiable list containing one element.
 795      *
 796      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 797      *
 798      * @param <E> the {@code List}'s element type
 799      * @param e1 the single element
 800      * @return a {@code List} containing the specified element
 801      * @throws NullPointerException if the element is {@code null}
 802      *
 803      * @since 9
 804      */
 805     static <E> List<E> of(E e1) {
 806         return new ImmutableCollections.List1<>(e1);
 807     }
 808 
 809     /**
 810      * Returns an unmodifiable list containing two elements.
 811      *
 812      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 813      *
 814      * @param <E> the {@code List}'s element type
 815      * @param e1 the first element
 816      * @param e2 the second element
 817      * @return a {@code List} containing the specified elements
 818      * @throws NullPointerException if an element is {@code null}
 819      *
 820      * @since 9
 821      */
 822     static <E> List<E> of(E e1, E e2) {
 823         return new ImmutableCollections.List2<>(e1, e2);
 824     }
 825 
 826     /**
 827      * Returns an unmodifiable list containing three elements.
 828      *
 829      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 830      *
 831      * @param <E> the {@code List}'s element type
 832      * @param e1 the first element
 833      * @param e2 the second element
 834      * @param e3 the third element
 835      * @return a {@code List} containing the specified elements
 836      * @throws NullPointerException if an element is {@code null}
 837      *
 838      * @since 9
 839      */
 840     static <E> List<E> of(E e1, E e2, E e3) {
 841         return new ImmutableCollections.ListN<>(e1, e2, e3);
 842     }
 843 
 844     /**
 845      * Returns an unmodifiable list containing four elements.
 846      *
 847      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 848      *
 849      * @param <E> the {@code List}'s element type
 850      * @param e1 the first element
 851      * @param e2 the second element
 852      * @param e3 the third element
 853      * @param e4 the fourth element
 854      * @return a {@code List} containing the specified elements
 855      * @throws NullPointerException if an element is {@code null}
 856      *
 857      * @since 9
 858      */
 859     static <E> List<E> of(E e1, E e2, E e3, E e4) {
 860         return new ImmutableCollections.ListN<>(e1, e2, e3, e4);
 861     }
 862 
 863     /**
 864      * Returns an unmodifiable list containing five elements.
 865      *
 866      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 867      *
 868      * @param <E> the {@code List}'s element type
 869      * @param e1 the first element
 870      * @param e2 the second element
 871      * @param e3 the third element
 872      * @param e4 the fourth element
 873      * @param e5 the fifth element
 874      * @return a {@code List} containing the specified elements
 875      * @throws NullPointerException if an element is {@code null}
 876      *
 877      * @since 9
 878      */
 879     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5) {
 880         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5);
 881     }
 882 
 883     /**
 884      * Returns an unmodifiable list containing six elements.
 885      *
 886      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 887      *
 888      * @param <E> the {@code List}'s element type
 889      * @param e1 the first element
 890      * @param e2 the second element
 891      * @param e3 the third element
 892      * @param e4 the fourth element
 893      * @param e5 the fifth element
 894      * @param e6 the sixth element
 895      * @return a {@code List} containing the specified elements
 896      * @throws NullPointerException if an element is {@code null}
 897      *
 898      * @since 9
 899      */
 900     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
 901         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
 902                                                 e6);
 903     }
 904 
 905     /**
 906      * Returns an unmodifiable list containing seven elements.
 907      *
 908      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 909      *
 910      * @param <E> the {@code List}'s element type
 911      * @param e1 the first element
 912      * @param e2 the second element
 913      * @param e3 the third element
 914      * @param e4 the fourth element
 915      * @param e5 the fifth element
 916      * @param e6 the sixth element
 917      * @param e7 the seventh element
 918      * @return a {@code List} containing the specified elements
 919      * @throws NullPointerException if an element is {@code null}
 920      *
 921      * @since 9
 922      */
 923     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
 924         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
 925                                                 e6, e7);
 926     }
 927 
 928     /**
 929      * Returns an unmodifiable list containing eight elements.
 930      *
 931      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 932      *
 933      * @param <E> the {@code List}'s element type
 934      * @param e1 the first element
 935      * @param e2 the second element
 936      * @param e3 the third element
 937      * @param e4 the fourth element
 938      * @param e5 the fifth element
 939      * @param e6 the sixth element
 940      * @param e7 the seventh element
 941      * @param e8 the eighth element
 942      * @return a {@code List} containing the specified elements
 943      * @throws NullPointerException if an element is {@code null}
 944      *
 945      * @since 9
 946      */
 947     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
 948         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
 949                                                 e6, e7, e8);
 950     }
 951 
 952     /**
 953      * Returns an unmodifiable list containing nine elements.
 954      *
 955      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 956      *
 957      * @param <E> the {@code List}'s element type
 958      * @param e1 the first element
 959      * @param e2 the second element
 960      * @param e3 the third element
 961      * @param e4 the fourth element
 962      * @param e5 the fifth element
 963      * @param e6 the sixth element
 964      * @param e7 the seventh element
 965      * @param e8 the eighth element
 966      * @param e9 the ninth element
 967      * @return a {@code List} containing the specified elements
 968      * @throws NullPointerException if an element is {@code null}
 969      *
 970      * @since 9
 971      */
 972     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
 973         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
 974                                                 e6, e7, e8, e9);
 975     }
 976 
 977     /**
 978      * Returns an unmodifiable list containing ten elements.
 979      *
 980      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
 981      *
 982      * @param <E> the {@code List}'s element type
 983      * @param e1 the first element
 984      * @param e2 the second element
 985      * @param e3 the third element
 986      * @param e4 the fourth element
 987      * @param e5 the fifth element
 988      * @param e6 the sixth element
 989      * @param e7 the seventh element
 990      * @param e8 the eighth element
 991      * @param e9 the ninth element
 992      * @param e10 the tenth element
 993      * @return a {@code List} containing the specified elements
 994      * @throws NullPointerException if an element is {@code null}
 995      *
 996      * @since 9
 997      */
 998     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
 999         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
1000                                                 e6, e7, e8, e9, e10);
1001     }
1002 
1003     /**
1004      * Returns an unmodifiable list containing an arbitrary number of elements.
1005      * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
1006      *
1007      * @apiNote
1008      * This method also accepts a single array as an argument. The element type of
1009      * the resulting list will be the component type of the array, and the size of
1010      * the list will be equal to the length of the array. To create a list with
1011      * a single element that is an array, do the following:
1012      *
1013      * <pre>{@code
1014      *     String[] array = ... ;
1015      *     List<String[]> list = List.<String[]>of(array);
1016      * }</pre>
1017      *
1018      * This will cause the {@link List#of(Object) List.of(E)} method
1019      * to be invoked instead.
1020      *
1021      * @param <E> the {@code List}'s element type
1022      * @param elements the elements to be contained in the list
1023      * @return a {@code List} containing the specified elements
1024      * @throws NullPointerException if an element is {@code null} or if the array is {@code null}
1025      *
1026      * @since 9
1027      */
1028     @SafeVarargs
1029     @SuppressWarnings("varargs")
1030     static <E> List<E> of(E... elements) {
1031         switch (elements.length) { // implicit null check of elements
1032             case 0:
1033                 return ImmutableCollections.List0.instance();
1034             case 1:
1035                 return new ImmutableCollections.List1<>(elements[0]);
1036             case 2:
1037                 return new ImmutableCollections.List2<>(elements[0], elements[1]);
1038             default:
1039                 return new ImmutableCollections.ListN<>(elements);
1040         }
1041     }
1042 
1043     /**
1044      * Returns an unmodifiable List containing the elements of the given Collection,
1045      * in iteration order. See <a href="#unmodifiable">Unmodifiable Lists</a> for
1046      * information about the characteristics of the returned List.
1047      *
1048      * @param <E> the {@code List}'s element type
1049      * @param coll the collection from which elements are drawn
1050      * @return the new List
1051      * @since 10
1052      */
1053     @SuppressWarnings("unchecked")
1054     static <E> List<E> copyOf(Collection<? extends E> coll) {
1055         if (coll instanceof ImmutableCollections.AbstractImmutableList) {
1056             return (List<E>)coll;
1057         } else {
1058             return (List<E>)List.of(coll.toArray());
1059         }
1060     }
1061 }
--- EOF ---