1 /*
2 * Copyright (c) 1997, 2014, 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 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 name="immutable">Immutable List Factory Methods</a></h2>
91 * <p>The {@link List#of(Object...) List.of()} factory methods
92 * provide a convenient way to create immutable lists. The {@code List}
93 * instances created by these methods have the following characteristics:
94 *
95 * <ul>
96 * <li>They cannot be modified. Attempts to modify them result in
97 * an {@code UnsupportedOperationException}.
98 * <li>They disallow null elements. Attempts to create them with
99 * null elements result in {@code NullPointerException}.
100 * <li>They are serializable if all elements are serializable.
101 * </ul>
102 *
103 * <p>This interface is a member of the
104 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
105 * Java Collections Framework</a>.
106 *
107 * @param <E> the type of elements in this list
108 *
109 * @author Josh Bloch
110 * @author Neal Gafter
111 * @see Collection
112 * @see Set
113 * @see ArrayList
114 * @see LinkedList
115 * @see Vector
116 * @see Arrays#asList(Object[])
117 * @see Collections#nCopies(int, Object)
118 * @see Collections#EMPTY_LIST
119 * @see AbstractList
120 * @see AbstractSequentialList
121 * @since 1.2
122 */
123
124 public interface List<E> extends Collection<E> {
125 // Query Operations
126
127 /**
128 * Returns the number of elements in this list. If this list contains
129 * more than {@code Integer.MAX_VALUE} elements, returns
130 * {@code Integer.MAX_VALUE}.
131 *
132 * @return the number of elements in this list
133 */
134 int size();
135
136 /**
137 * Returns {@code true} if this list contains no elements.
138 *
139 * @return {@code true} if this list contains no elements
140 */
141 boolean isEmpty();
142
143 /**
144 * Returns {@code true} if this list contains the specified element.
145 * More formally, returns {@code true} if and only if this list contains
146 * at least one element {@code e} such that
147 * {@code Objects.equals(o, e)}.
148 *
149 * @param o element whose presence in this list is to be tested
150 * @return {@code true} if this list contains the specified element
151 * @throws ClassCastException if the type of the specified element
152 * is incompatible with this list
153 * (<a href="Collection.html#optional-restrictions">optional</a>)
154 * @throws NullPointerException if the specified element is null and this
155 * list does not permit null elements
156 * (<a href="Collection.html#optional-restrictions">optional</a>)
157 */
158 boolean contains(Object o);
159
160 /**
161 * Returns an iterator over the elements in this list in proper sequence.
162 *
163 * @return an iterator over the elements in this list in proper sequence
164 */
165 Iterator<E> iterator();
166
167 /**
168 * Returns an array containing all of the elements in this list in proper
169 * sequence (from first to last element).
170 *
171 * <p>The returned array will be "safe" in that no references to it are
172 * maintained by this list. (In other words, this method must
173 * allocate a new array even if this list is backed by an array).
174 * The caller is thus free to modify the returned array.
175 *
176 * <p>This method acts as bridge between array-based and collection-based
177 * APIs.
178 *
179 * @return an array containing all of the elements in this list in proper
180 * sequence
181 * @see Arrays#asList(Object[])
182 */
183 Object[] toArray();
184
185 /**
186 * Returns an array containing all of the elements in this list in
187 * proper sequence (from first to last element); the runtime type of
188 * the returned array is that of the specified array. If the list fits
189 * in the specified array, it is returned therein. Otherwise, a new
190 * array is allocated with the runtime type of the specified array and
191 * the size of this list.
192 *
193 * <p>If the list fits in the specified array with room to spare (i.e.,
194 * the array has more elements than the list), the element in the array
195 * immediately following the end of the list is set to {@code null}.
196 * (This is useful in determining the length of the list <i>only</i> if
197 * the caller knows that the list does not contain any null elements.)
198 *
199 * <p>Like the {@link #toArray()} method, this method acts as bridge between
200 * array-based and collection-based APIs. Further, this method allows
201 * precise control over the runtime type of the output array, and may,
202 * under certain circumstances, be used to save allocation costs.
203 *
204 * <p>Suppose {@code x} is a list known to contain only strings.
205 * The following code can be used to dump the list into a newly
206 * allocated array of {@code String}:
207 *
208 * <pre>{@code
209 * String[] y = x.toArray(new String[0]);
210 * }</pre>
211 *
212 * Note that {@code toArray(new Object[0])} is identical in function to
213 * {@code toArray()}.
214 *
215 * @param a the array into which the elements of this list are to
216 * be stored, if it is big enough; otherwise, a new array of the
217 * same runtime type is allocated for this purpose.
218 * @return an array containing the elements of this list
219 * @throws ArrayStoreException if the runtime type of the specified array
220 * is not a supertype of the runtime type of every element in
221 * this list
222 * @throws NullPointerException if the specified array is null
223 */
224 <T> T[] toArray(T[] a);
225
226
227 // Modification Operations
228
229 /**
230 * Appends the specified element to the end of this list (optional
231 * operation).
232 *
233 * <p>Lists that support this operation may place limitations on what
234 * elements may be added to this list. In particular, some
235 * lists will refuse to add null elements, and others will impose
236 * restrictions on the type of elements that may be added. List
237 * classes should clearly specify in their documentation any restrictions
238 * on what elements may be added.
239 *
240 * @param e element to be appended to this list
241 * @return {@code true} (as specified by {@link Collection#add})
242 * @throws UnsupportedOperationException if the {@code add} operation
243 * is not supported by this list
244 * @throws ClassCastException if the class of the specified element
245 * prevents it from being added to this list
246 * @throws NullPointerException if the specified element is null and this
247 * list does not permit null elements
248 * @throws IllegalArgumentException if some property of this element
249 * prevents it from being added to this list
250 */
251 boolean add(E e);
252
253 /**
254 * Removes the first occurrence of the specified element from this list,
255 * if it is present (optional operation). If this list does not contain
256 * the element, it is unchanged. More formally, removes the element with
257 * the lowest index {@code i} such that
258 * {@code Objects.equals(o, get(i))}
259 * (if such an element exists). Returns {@code true} if this list
260 * contained the specified element (or equivalently, if this list changed
261 * as a result of the call).
262 *
263 * @param o element to be removed from this list, if present
264 * @return {@code true} if this list contained the specified element
265 * @throws ClassCastException if the type of the specified element
266 * is incompatible with this list
267 * (<a href="Collection.html#optional-restrictions">optional</a>)
268 * @throws NullPointerException if the specified element is null and this
269 * list does not permit null elements
270 * (<a href="Collection.html#optional-restrictions">optional</a>)
271 * @throws UnsupportedOperationException if the {@code remove} operation
272 * is not supported by this list
273 */
274 boolean remove(Object o);
275
276
277 // Bulk Modification Operations
278
279 /**
280 * Returns {@code true} if this list contains all of the elements of the
281 * specified collection.
282 *
283 * @param c collection to be checked for containment in this list
284 * @return {@code true} if this list contains all of the elements of the
285 * specified collection
286 * @throws ClassCastException if the types of one or more elements
287 * in the specified collection are incompatible with this
288 * list
289 * (<a href="Collection.html#optional-restrictions">optional</a>)
290 * @throws NullPointerException if the specified collection contains one
291 * or more null elements and this list does not permit null
292 * elements
293 * (<a href="Collection.html#optional-restrictions">optional</a>),
294 * or if the specified collection is null
295 * @see #contains(Object)
296 */
297 boolean containsAll(Collection<?> c);
298
299 /**
300 * Appends all of the elements in the specified collection to the end of
301 * this list, in the order that they are returned by the specified
302 * collection's iterator (optional operation). The behavior of this
303 * operation is undefined if the specified collection is modified while
304 * the operation is in progress. (Note that this will occur if the
305 * specified collection is this list, and it's nonempty.)
306 *
307 * @param c collection containing elements to be added to this list
308 * @return {@code true} if this list changed as a result of the call
309 * @throws UnsupportedOperationException if the {@code addAll} operation
310 * is not supported by this list
311 * @throws ClassCastException if the class of an element of the specified
312 * collection prevents it from being added to this list
313 * @throws NullPointerException if the specified collection contains one
314 * or more null elements and this list does not permit null
315 * elements, or if the specified collection is null
316 * @throws IllegalArgumentException if some property of an element of the
317 * specified collection prevents it from being added to this list
318 * @see #add(Object)
319 */
320 boolean addAll(Collection<? extends E> c);
321
322 /**
323 * Inserts all of the elements in the specified collection into this
324 * list at the specified position (optional operation). Shifts the
325 * element currently at that position (if any) and any subsequent
326 * elements to the right (increases their indices). The new elements
327 * will appear in this list in the order that they are returned by the
328 * specified collection's iterator. The behavior of this operation is
329 * undefined if the specified collection is modified while the
330 * operation is in progress. (Note that this will occur if the specified
331 * collection is this list, and it's nonempty.)
332 *
333 * @param index index at which to insert the first element from the
334 * specified collection
335 * @param c collection containing elements to be added to this list
336 * @return {@code true} if this list changed as a result of the call
337 * @throws UnsupportedOperationException if the {@code addAll} operation
338 * is not supported by this list
339 * @throws ClassCastException if the class of an element of the specified
340 * collection prevents it from being added to this list
341 * @throws NullPointerException if the specified collection contains one
342 * or more null elements and this list does not permit null
343 * elements, or if the specified collection is null
344 * @throws IllegalArgumentException if some property of an element of the
345 * specified collection prevents it from being added to this list
346 * @throws IndexOutOfBoundsException if the index is out of range
347 * ({@code index < 0 || index > size()})
348 */
349 boolean addAll(int index, Collection<? extends E> c);
350
351 /**
352 * Removes from this list all of its elements that are contained in the
353 * specified collection (optional operation).
354 *
355 * @param c collection containing elements to be removed from this list
356 * @return {@code true} if this list changed as a result of the call
357 * @throws UnsupportedOperationException if the {@code removeAll} operation
358 * is not supported by this list
359 * @throws ClassCastException if the class of an element of this list
360 * is incompatible with the specified collection
361 * (<a href="Collection.html#optional-restrictions">optional</a>)
362 * @throws NullPointerException if this list contains a null element and the
363 * specified collection does not permit null elements
364 * (<a href="Collection.html#optional-restrictions">optional</a>),
365 * or if the specified collection is null
366 * @see #remove(Object)
367 * @see #contains(Object)
368 */
369 boolean removeAll(Collection<?> c);
370
371 /**
372 * Retains only the elements in this list that are contained in the
373 * specified collection (optional operation). In other words, removes
374 * from this list all of its elements that are not contained in the
375 * specified collection.
376 *
377 * @param c collection containing elements to be retained in this list
378 * @return {@code true} if this list changed as a result of the call
379 * @throws UnsupportedOperationException if the {@code retainAll} operation
380 * is not supported by this list
381 * @throws ClassCastException if the class of an element of this list
382 * is incompatible with the specified collection
383 * (<a href="Collection.html#optional-restrictions">optional</a>)
384 * @throws NullPointerException if this list contains a null element and the
385 * specified collection does not permit null elements
386 * (<a href="Collection.html#optional-restrictions">optional</a>),
387 * or if the specified collection is null
388 * @see #remove(Object)
389 * @see #contains(Object)
390 */
391 boolean retainAll(Collection<?> c);
392
393 /**
394 * Replaces each element of this list with the result of applying the
395 * operator to that element. Errors or runtime exceptions thrown by
396 * the operator are relayed to the caller.
397 *
398 * @implSpec
399 * The default implementation is equivalent to, for this {@code list}:
400 * <pre>{@code
401 * final ListIterator<E> li = list.listIterator();
402 * while (li.hasNext()) {
403 * li.set(operator.apply(li.next()));
404 * }
405 * }</pre>
406 *
407 * If the list's list-iterator does not support the {@code set} operation
408 * then an {@code UnsupportedOperationException} will be thrown when
409 * replacing the first element.
410 *
411 * @param operator the operator to apply to each element
412 * @throws UnsupportedOperationException if this list is unmodifiable.
413 * Implementations may throw this exception if an element
414 * cannot be replaced or if, in general, modification is not
415 * supported
416 * @throws NullPointerException if the specified operator is null or
417 * if the operator result is a null value and this list does
418 * not permit null elements
419 * (<a href="Collection.html#optional-restrictions">optional</a>)
420 * @since 1.8
421 */
422 default void replaceAll(UnaryOperator<E> operator) {
423 Objects.requireNonNull(operator);
424 final ListIterator<E> li = this.listIterator();
425 while (li.hasNext()) {
426 li.set(operator.apply(li.next()));
427 }
428 }
429
430 /**
431 * Sorts this list according to the order induced by the specified
432 * {@link Comparator}.
433 *
434 * <p>All elements in this list must be <i>mutually comparable</i> using the
435 * specified comparator (that is, {@code c.compare(e1, e2)} must not throw
436 * a {@code ClassCastException} for any elements {@code e1} and {@code e2}
437 * in the list).
438 *
439 * <p>If the specified comparator is {@code null} then all elements in this
440 * list must implement the {@link Comparable} interface and the elements'
441 * {@linkplain Comparable natural ordering} should be used.
442 *
443 * <p>This list must be modifiable, but need not be resizable.
444 *
445 * @implSpec
446 * The default implementation obtains an array containing all elements in
447 * this list, sorts the array, and iterates over this list resetting each
448 * element from the corresponding position in the array. (This avoids the
449 * n<sup>2</sup> log(n) performance that would result from attempting
450 * to sort a linked list in place.)
451 *
452 * @implNote
453 * This implementation is a stable, adaptive, iterative mergesort that
454 * requires far fewer than n lg(n) comparisons when the input array is
455 * partially sorted, while offering the performance of a traditional
456 * mergesort when the input array is randomly ordered. If the input array
457 * is nearly sorted, the implementation requires approximately n
458 * comparisons. Temporary storage requirements vary from a small constant
459 * for nearly sorted input arrays to n/2 object references for randomly
460 * ordered input arrays.
461 *
462 * <p>The implementation takes equal advantage of ascending and
463 * descending order in its input array, and can take advantage of
464 * ascending and descending order in different parts of the same
465 * input array. It is well-suited to merging two or more sorted arrays:
466 * simply concatenate the arrays and sort the resulting array.
467 *
468 * <p>The implementation was adapted from Tim Peters's list sort for Python
469 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
470 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
471 * Sorting and Information Theoretic Complexity", in Proceedings of the
472 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
473 * January 1993.
474 *
475 * @param c the {@code Comparator} used to compare list elements.
476 * A {@code null} value indicates that the elements'
477 * {@linkplain Comparable natural ordering} should be used
478 * @throws ClassCastException if the list contains elements that are not
479 * <i>mutually comparable</i> using the specified comparator
480 * @throws UnsupportedOperationException if the list's list-iterator does
481 * not support the {@code set} operation
482 * @throws IllegalArgumentException
483 * (<a href="Collection.html#optional-restrictions">optional</a>)
484 * if the comparator is found to violate the {@link Comparator}
485 * contract
486 * @since 1.8
487 */
488 @SuppressWarnings({"unchecked", "rawtypes"})
489 default void sort(Comparator<? super E> c) {
490 Object[] a = this.toArray();
491 Arrays.sort(a, (Comparator) c);
492 ListIterator<E> i = this.listIterator();
493 for (Object e : a) {
494 i.next();
495 i.set((E) e);
496 }
497 }
498
499 /**
500 * Removes all of the elements from this list (optional operation).
501 * The list will be empty after this call returns.
502 *
503 * @throws UnsupportedOperationException if the {@code clear} operation
504 * is not supported by this list
505 */
506 void clear();
507
508
509 // Comparison and hashing
510
511 /**
512 * Compares the specified object with this list for equality. Returns
513 * {@code true} if and only if the specified object is also a list, both
514 * lists have the same size, and all corresponding pairs of elements in
515 * the two lists are <i>equal</i>. (Two elements {@code e1} and
516 * {@code e2} are <i>equal</i> if {@code Objects.equals(e1, e2)}.)
517 * In other words, two lists are defined to be
518 * equal if they contain the same elements in the same order. This
519 * definition ensures that the equals method works properly across
520 * different implementations of the {@code List} interface.
521 *
522 * @param o the object to be compared for equality with this list
523 * @return {@code true} if the specified object is equal to this list
524 */
525 boolean equals(Object o);
526
527 /**
528 * Returns the hash code value for this list. The hash code of a list
529 * is defined to be the result of the following calculation:
530 * <pre>{@code
531 * int hashCode = 1;
532 * for (E e : list)
533 * hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
534 * }</pre>
535 * This ensures that {@code list1.equals(list2)} implies that
536 * {@code list1.hashCode()==list2.hashCode()} for any two lists,
537 * {@code list1} and {@code list2}, as required by the general
538 * contract of {@link Object#hashCode}.
539 *
540 * @return the hash code value for this list
541 * @see Object#equals(Object)
542 * @see #equals(Object)
543 */
544 int hashCode();
545
546
547 // Positional Access Operations
548
549 /**
550 * Returns the element at the specified position in this list.
551 *
552 * @param index index of the element to return
553 * @return the element at the specified position in this list
554 * @throws IndexOutOfBoundsException if the index is out of range
555 * ({@code index < 0 || index >= size()})
556 */
557 E get(int index);
558
559 /**
560 * Replaces the element at the specified position in this list with the
561 * specified element (optional operation).
562 *
563 * @param index index of the element to replace
564 * @param element element to be stored at the specified position
565 * @return the element previously at the specified position
566 * @throws UnsupportedOperationException if the {@code set} operation
567 * is not supported by this list
568 * @throws ClassCastException if the class of the specified element
569 * prevents it from being added to this list
570 * @throws NullPointerException if the specified element is null and
571 * this list does not permit null elements
572 * @throws IllegalArgumentException if some property of the specified
573 * element prevents it from being added to this list
574 * @throws IndexOutOfBoundsException if the index is out of range
575 * ({@code index < 0 || index >= size()})
576 */
577 E set(int index, E element);
578
579 /**
580 * Inserts the specified element at the specified position in this list
581 * (optional operation). Shifts the element currently at that position
582 * (if any) and any subsequent elements to the right (adds one to their
583 * indices).
584 *
585 * @param index index at which the specified element is to be inserted
586 * @param element element to be inserted
587 * @throws UnsupportedOperationException if the {@code add} operation
588 * is not supported by this list
589 * @throws ClassCastException if the class of the specified element
590 * prevents it from being added to this list
591 * @throws NullPointerException if the specified element is null and
592 * this list does not permit null elements
593 * @throws IllegalArgumentException if some property of the specified
594 * element prevents it from being added to this list
595 * @throws IndexOutOfBoundsException if the index is out of range
596 * ({@code index < 0 || index > size()})
597 */
598 void add(int index, E element);
599
600 /**
601 * Removes the element at the specified position in this list (optional
602 * operation). Shifts any subsequent elements to the left (subtracts one
603 * from their indices). Returns the element that was removed from the
604 * list.
605 *
606 * @param index the index of the element to be removed
607 * @return the element previously at the specified position
608 * @throws UnsupportedOperationException if the {@code remove} operation
609 * is not supported by this list
610 * @throws IndexOutOfBoundsException if the index is out of range
611 * ({@code index < 0 || index >= size()})
612 */
613 E remove(int index);
614
615
616 // Search Operations
617
618 /**
619 * Returns the index of the first occurrence of the specified element
620 * in this list, or -1 if this list does not contain the element.
621 * More formally, returns the lowest index {@code i} such that
622 * {@code Objects.equals(o, get(i))},
623 * or -1 if there is no such index.
624 *
625 * @param o element to search for
626 * @return the index of the first occurrence of the specified element in
627 * this list, or -1 if this list does not contain the element
628 * @throws ClassCastException if the type of the specified element
629 * is incompatible with this list
630 * (<a href="Collection.html#optional-restrictions">optional</a>)
631 * @throws NullPointerException if the specified element is null and this
632 * list does not permit null elements
633 * (<a href="Collection.html#optional-restrictions">optional</a>)
634 */
635 int indexOf(Object o);
636
637 /**
638 * Returns the index of the last occurrence of the specified element
639 * in this list, or -1 if this list does not contain the element.
640 * More formally, returns the highest index {@code i} such that
641 * {@code Objects.equals(o, get(i))},
642 * or -1 if there is no such index.
643 *
644 * @param o element to search for
645 * @return the index of the last occurrence of the specified element in
646 * this list, or -1 if this list does not contain the element
647 * @throws ClassCastException if the type of the specified element
648 * is incompatible with this list
649 * (<a href="Collection.html#optional-restrictions">optional</a>)
650 * @throws NullPointerException if the specified element is null and this
651 * list does not permit null elements
652 * (<a href="Collection.html#optional-restrictions">optional</a>)
653 */
654 int lastIndexOf(Object o);
655
656
657 // List Iterators
658
659 /**
660 * Returns a list iterator over the elements in this list (in proper
661 * sequence).
662 *
663 * @return a list iterator over the elements in this list (in proper
664 * sequence)
665 */
666 ListIterator<E> listIterator();
667
668 /**
669 * Returns a list iterator over the elements in this list (in proper
670 * sequence), starting at the specified position in the list.
671 * The specified index indicates the first element that would be
672 * returned by an initial call to {@link ListIterator#next next}.
673 * An initial call to {@link ListIterator#previous previous} would
674 * return the element with the specified index minus one.
675 *
676 * @param index index of the first element to be returned from the
677 * list iterator (by a call to {@link ListIterator#next next})
678 * @return a list iterator over the elements in this list (in proper
679 * sequence), starting at the specified position in the list
680 * @throws IndexOutOfBoundsException if the index is out of range
681 * ({@code index < 0 || index > size()})
682 */
683 ListIterator<E> listIterator(int index);
684
685 // View
686
687 /**
688 * Returns a view of the portion of this list between the specified
689 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
690 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
691 * empty.) The returned list is backed by this list, so non-structural
692 * changes in the returned list are reflected in this list, and vice-versa.
693 * The returned list supports all of the optional list operations supported
694 * by this list.<p>
695 *
696 * This method eliminates the need for explicit range operations (of
697 * the sort that commonly exist for arrays). Any operation that expects
698 * a list can be used as a range operation by passing a subList view
699 * instead of a whole list. For example, the following idiom
700 * removes a range of elements from a list:
701 * <pre>{@code
702 * list.subList(from, to).clear();
703 * }</pre>
704 * Similar idioms may be constructed for {@code indexOf} and
705 * {@code lastIndexOf}, and all of the algorithms in the
706 * {@code Collections} class can be applied to a subList.<p>
707 *
708 * The semantics of the list returned by this method become undefined if
709 * the backing list (i.e., this list) is <i>structurally modified</i> in
710 * any way other than via the returned list. (Structural modifications are
711 * those that change the size of this list, or otherwise perturb it in such
712 * a fashion that iterations in progress may yield incorrect results.)
713 *
714 * @param fromIndex low endpoint (inclusive) of the subList
715 * @param toIndex high endpoint (exclusive) of the subList
716 * @return a view of the specified range within this list
717 * @throws IndexOutOfBoundsException for an illegal endpoint index value
718 * ({@code fromIndex < 0 || toIndex > size ||
719 * fromIndex > toIndex})
720 */
721 List<E> subList(int fromIndex, int toIndex);
722
723 /**
724 * Creates a {@link Spliterator} over the elements in this list.
725 *
726 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
727 * {@link Spliterator#ORDERED}. Implementations should document the
728 * reporting of additional characteristic values.
729 *
730 * @implSpec
731 * The default implementation creates a
732 * <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
733 * from the list's {@code Iterator}. The spliterator inherits the
734 * <em>fail-fast</em> properties of the list's iterator.
735 *
736 * @implNote
737 * The created {@code Spliterator} additionally reports
738 * {@link Spliterator#SUBSIZED}.
739 *
740 * @return a {@code Spliterator} over the elements in this list
741 * @since 1.8
742 */
743 @Override
744 default Spliterator<E> spliterator() {
745 return Spliterators.spliterator(this, Spliterator.ORDERED);
746 }
747
748 /**
749 * Creates an immutable list containing zero elements.
750 *
751 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
752 *
753 * @param <E> the list's element type
754 * @return the newly created list
755 *
756 * @since 1.9
757 */
758 static <E> List<E> of() {
759 return Collections.emptyList();
760 }
761
762 /**
763 * Creates an immutable list containing one element.
764 *
765 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
766 *
767 * @param <E> the list's element type
768 * @param e1 the single list element
769 * @return the newly created list
770 * @throws NullPointerException if the element is null
771 *
772 * @since 1.9
773 */
774 static <E> List<E> of(E e1) {
775 return Collections.singletonList(Objects.requireNonNull(e1));
776 }
777
778 /**
779 * Creates an immutable list containing two elements.
780 *
781 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
782 *
783 * @param <E> the list's element type
784 * @param e1 the first list element
785 * @param e2 the second list element
786 * @return the newly created list
787 * @throws NullPointerException if an element is null
788 *
789 * @since 1.9
790 */
791 static <E> List<E> of(E e1, E e2) {
792 return Collections.unmodifiableList(
793 Arrays.asList(Objects.requireNonNull(e1),
794 Objects.requireNonNull(e2)));
795 }
796
797 /**
798 * Creates an immutable list containing three elements.
799 *
800 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
801 *
802 * @param <E> the list's element type
803 * @param e1 the first list element
804 * @param e2 the second list element
805 * @param e3 the third list element
806 * @return the newly created list
807 * @throws NullPointerException if an element is null
808 *
809 * @since 1.9
810 */
811 static <E> List<E> of(E e1, E e2, E e3) {
812 return Collections.unmodifiableList(
813 Arrays.asList(Objects.requireNonNull(e1),
814 Objects.requireNonNull(e2),
815 Objects.requireNonNull(e3)));
816 }
817
818 /**
819 * Creates an immutable list containing four elements.
820 *
821 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
822 *
823 * @param <E> the list's element type
824 * @param e1 the first list element
825 * @param e2 the second list element
826 * @param e3 the third list element
827 * @param e4 the fourth list element
828 * @return the newly created list
829 * @throws NullPointerException if an element is null
830 *
831 * @since 1.9
832 */
833 static <E> List<E> of(E e1, E e2, E e3, E e4) {
834 return Collections.unmodifiableList(
835 Arrays.asList(Objects.requireNonNull(e1),
836 Objects.requireNonNull(e2),
837 Objects.requireNonNull(e3),
838 Objects.requireNonNull(e4)));
839 }
840
841 /**
842 * Creates an immutable list containing five elements.
843 *
844 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
845 *
846 * @param <E> the list's element type
847 * @param e1 the first list element
848 * @param e2 the second list element
849 * @param e3 the third list element
850 * @param e4 the fourth list element
851 * @param e5 the fifth list element
852 * @return the newly created list
853 * @throws NullPointerException if an element is null
854 *
855 * @since 1.9
856 */
857 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5) {
858 return Collections.unmodifiableList(
859 Arrays.asList(Objects.requireNonNull(e1),
860 Objects.requireNonNull(e2),
861 Objects.requireNonNull(e3),
862 Objects.requireNonNull(e4),
863 Objects.requireNonNull(e5)));
864 }
865
866 /**
867 * Creates an immutable list containing six elements.
868 *
869 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
870 *
871 * @param <E> the list's element type
872 * @param e1 the first list element
873 * @param e2 the second list element
874 * @param e3 the third list element
875 * @param e4 the fourth list element
876 * @param e5 the fifth list element
877 * @param e6 the sixth list element
878 * @return the newly created list
879 * @throws NullPointerException if an element is null
880 *
881 * @since 1.9
882 */
883 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
884 return Collections.unmodifiableList(
885 Arrays.asList(Objects.requireNonNull(e1),
886 Objects.requireNonNull(e2),
887 Objects.requireNonNull(e3),
888 Objects.requireNonNull(e4),
889 Objects.requireNonNull(e5),
890 Objects.requireNonNull(e6)));
891 }
892
893 /**
894 * Creates an immutable list containing seven elements.
895 *
896 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
897 *
898 * @param <E> the list's element type
899 * @param e1 the first list element
900 * @param e2 the second list element
901 * @param e3 the third list element
902 * @param e4 the fourth list element
903 * @param e5 the fifth list element
904 * @param e6 the sixth list element
905 * @param e7 the seventh list element
906 * @return the newly created list
907 * @throws NullPointerException if an element is null
908 *
909 * @since 1.9
910 */
911 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
912 return Collections.unmodifiableList(
913 Arrays.asList(Objects.requireNonNull(e1),
914 Objects.requireNonNull(e2),
915 Objects.requireNonNull(e3),
916 Objects.requireNonNull(e4),
917 Objects.requireNonNull(e5),
918 Objects.requireNonNull(e6),
919 Objects.requireNonNull(e7)));
920 }
921
922 /**
923 * Creates an immutable list containing eight elements.
924 *
925 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
926 *
927 * @param <E> the list's element type
928 * @param e1 the first list element
929 * @param e2 the second list element
930 * @param e3 the third list element
931 * @param e4 the fourth list element
932 * @param e5 the fifth list element
933 * @param e6 the sixth list element
934 * @param e7 the seventh list element
935 * @param e8 the eighth list element
936 * @return the newly created list
937 * @throws NullPointerException if an element is null
938 *
939 * @since 1.9
940 */
941 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
942 return Collections.unmodifiableList(
943 Arrays.asList(Objects.requireNonNull(e1),
944 Objects.requireNonNull(e2),
945 Objects.requireNonNull(e3),
946 Objects.requireNonNull(e4),
947 Objects.requireNonNull(e5),
948 Objects.requireNonNull(e6),
949 Objects.requireNonNull(e7),
950 Objects.requireNonNull(e8)));
951 }
952
953 /**
954 * Creates an immutable list containing nine elements.
955 *
956 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
957 *
958 * @param <E> the list's element type
959 * @param e1 the first list element
960 * @param e2 the second list element
961 * @param e3 the third list element
962 * @param e4 the fourth list element
963 * @param e5 the fifth list element
964 * @param e6 the sixth list element
965 * @param e7 the seventh list element
966 * @param e8 the eighth list element
967 * @param e9 the ninth list element
968 * @return the newly created list
969 * @throws NullPointerException if an element is null
970 *
971 * @since 1.9
972 */
973 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
974 return Collections.unmodifiableList(
975 Arrays.asList(Objects.requireNonNull(e1),
976 Objects.requireNonNull(e2),
977 Objects.requireNonNull(e3),
978 Objects.requireNonNull(e4),
979 Objects.requireNonNull(e5),
980 Objects.requireNonNull(e6),
981 Objects.requireNonNull(e7),
982 Objects.requireNonNull(e8),
983 Objects.requireNonNull(e9)));
984 }
985
986 /**
987 * Creates an immutable list containing ten elements.
988 *
989 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
990 *
991 * @param <E> the list's element type
992 * @param e1 the first list element
993 * @param e2 the second list element
994 * @param e3 the third list element
995 * @param e4 the fourth list element
996 * @param e5 the fifth list element
997 * @param e6 the sixth list element
998 * @param e7 the seventh list element
999 * @param e8 the eighth list element
1000 * @param e9 the ninth list element
1001 * @param e10 the tenth list element
1002 * @return the newly created list
1003 * @throws NullPointerException if an element is null
1004 *
1005 * @since 1.9
1006 */
1007 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) {
1008 return Collections.unmodifiableList(
1009 Arrays.asList(Objects.requireNonNull(e1),
1010 Objects.requireNonNull(e2),
1011 Objects.requireNonNull(e3),
1012 Objects.requireNonNull(e4),
1013 Objects.requireNonNull(e5),
1014 Objects.requireNonNull(e6),
1015 Objects.requireNonNull(e7),
1016 Objects.requireNonNull(e8),
1017 Objects.requireNonNull(e9),
1018 Objects.requireNonNull(e10)));
1019 }
1020
1021 /**
1022 * Creates an immutable list containing an arbitrary number of elements.
1023 *
1024 * See <a href="#immutable">Immutable List Factory Methods</a> for details.
1025 *
1026 * @apiNote
1027 * This method also accepts a single array as an argument. The element type of
1028 * the resulting list will be the component type of the array, and the size of
1029 * the list will be equal to the length of the array. To create a list with
1030 * a single element that is an array, do the following:
1031 *
1032 * <pre>{@code
1033 * String[] array = ... ;
1034 * List<String[]> list = List.<String[]>of(array);
1035 * }</pre>
1036 *
1037 * This will cause the {@link List#of(Object) List.of(E)} method
1038 * to be invoked instead.
1039 *
1040 * @param <E> the list's element type
1041 * @param es the elements to be contained in the list
1042 * @return the newly created list
1043 * @throws NullPointerException if an element is null
1044 *
1045 * @since 1.9
1046 */
1047 @SafeVarargs
1048 @SuppressWarnings("varargs")
1049 static <E> List<E> of(E... es) {
1050 for (E e : es) {
1051 Objects.requireNonNull(e);
1052 }
1053 // NOTE: this can allow a null element to slip through
1054 return Collections.unmodifiableList(Arrays.asList(es));
1055 }
1056 }