1 /*
2 * Copyright (c) 1997, 2019, 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
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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 *
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20 *
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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.base/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. This operation uses the membership semantics
296 * of this list.
297 *
298 * @param c collection to be checked for containment in this list
299 * @return {@code true} if this list contains all of the elements of the
300 * specified collection
301 * @throws ClassCastException if the types of one or more elements
302 * in the specified collection are incompatible with this
303 * list
304 * (<a href="Collection.html#optional-restrictions">optional</a>)
305 * @throws NullPointerException if the specified collection contains one
306 * or more null elements and this list does not permit null
307 * elements
308 * (<a href="Collection.html#optional-restrictions">optional</a>),
309 * or if the specified collection is null
310 * @see #contains(Object)
311 */
312 boolean containsAll(Collection<?> c);
313
314 /**
315 * Appends all of the elements in the specified collection to the end of
316 * this list, in the order that they are returned by the specified
317 * collection's iterator (optional operation). The behavior of this
318 * operation is undefined if the specified collection is modified while
319 * the operation is in progress. (Note that this will occur if the
320 * specified collection is this list, and it's nonempty.)
321 *
322 * @param c collection containing elements to be added to this list
323 * @return {@code true} if this list changed as a result of the call
324 * @throws UnsupportedOperationException if the {@code addAll} operation
325 * is not supported by this list
326 * @throws ClassCastException if the class of an element of the specified
327 * collection prevents it from being added to this list
328 * @throws NullPointerException if the specified collection contains one
329 * or more null elements and this list does not permit null
330 * elements, or if the specified collection is null
331 * @throws IllegalArgumentException if some property of an element of the
332 * specified collection prevents it from being added to this list
333 * @see #add(Object)
334 */
335 boolean addAll(Collection<? extends E> c);
336
337 /**
338 * Inserts all of the elements in the specified collection into this
339 * list at the specified position (optional operation). Shifts the
340 * element currently at that position (if any) and any subsequent
341 * elements to the right (increases their indices). The new elements
342 * will appear in this list in the order that they are returned by the
343 * specified collection's iterator. The behavior of this operation is
344 * undefined if the specified collection is modified while the
345 * operation is in progress. (Note that this will occur if the specified
346 * collection is this list, and it's nonempty.)
347 *
348 * @param index index at which to insert the first element from the
349 * specified collection
350 * @param c collection containing elements to be added to this list
351 * @return {@code true} if this list changed as a result of the call
352 * @throws UnsupportedOperationException if the {@code addAll} operation
353 * is not supported by this list
354 * @throws ClassCastException if the class of an element of the specified
355 * collection prevents it from being added to this list
356 * @throws NullPointerException if the specified collection contains one
357 * or more null elements and this list does not permit null
358 * elements, or if the specified collection is null
359 * @throws IllegalArgumentException if some property of an element of the
360 * specified collection prevents it from being added to this list
361 * @throws IndexOutOfBoundsException if the index is out of range
362 * ({@code index < 0 || index > size()})
363 */
364 boolean addAll(int index, Collection<? extends E> c);
365
366 /**
367 * Removes from this list all of its elements that are contained in the
368 * specified collection (optional operation). This operation uses the
369 * membership semantics of the specified collection.
370 *
371 * @implNote
372 * {@inheritDoc}
373 *
374 * @param c collection containing elements to be removed from this list
375 * @return {@code true} if this list changed as a result of the call
376 * @throws UnsupportedOperationException if the {@code removeAll} operation
377 * is not supported by this list
378 * @throws ClassCastException if the class of an element of this list
379 * is incompatible with the specified collection
380 * (<a href="Collection.html#optional-restrictions">optional</a>)
381 * @throws NullPointerException if this list contains a null element and the
382 * specified collection does not permit null elements
383 * (<a href="Collection.html#optional-restrictions">optional</a>),
384 * or if the specified collection is null
385 * @see #remove(Object)
386 * @see #contains(Object)
387 */
388 boolean removeAll(Collection<?> c);
389
390 /**
391 * Retains only the elements in this list that are contained in the
392 * specified collection (optional operation). In other words, removes
393 * from this list all of its elements that are not contained in the
394 * specified collection. This operation uses the membership semantics of
395 * the specified collection.
396 *
397 * @implNote
398 * {@inheritDoc}
399 *
400 * @param c collection containing elements to be retained in this list
401 * @return {@code true} if this list changed as a result of the call
402 * @throws UnsupportedOperationException if the {@code retainAll} operation
403 * is not supported by this list
404 * @throws ClassCastException if the class of an element of this list
405 * is incompatible with the specified collection
406 * (<a href="Collection.html#optional-restrictions">optional</a>)
407 * @throws NullPointerException if this list contains a null element and the
408 * specified collection does not permit null elements
409 * (<a href="Collection.html#optional-restrictions">optional</a>),
410 * or if the specified collection is null
411 * @see #remove(Object)
412 * @see #contains(Object)
413 */
414 boolean retainAll(Collection<?> c);
415
416 /**
417 * Replaces each element of this list with the result of applying the
418 * operator to that element. Errors or runtime exceptions thrown by
419 * the operator are relayed to the caller.
420 *
421 * @implSpec
422 * The default implementation is equivalent to, for this {@code list}:
423 * <pre>{@code
424 * final ListIterator<E> li = list.listIterator();
425 * while (li.hasNext()) {
426 * li.set(operator.apply(li.next()));
427 * }
428 * }</pre>
429 *
430 * If the list's list-iterator does not support the {@code set} operation
431 * then an {@code UnsupportedOperationException} will be thrown when
432 * replacing the first element.
433 *
434 * @param operator the operator to apply to each element
435 * @throws UnsupportedOperationException if this list is unmodifiable.
436 * Implementations may throw this exception if an element
437 * cannot be replaced or if, in general, modification is not
438 * supported
439 * @throws NullPointerException if the specified operator is null or
440 * if the operator result is a null value and this list does
441 * not permit null elements
442 * (<a href="Collection.html#optional-restrictions">optional</a>)
443 * @since 1.8
444 */
445 default void replaceAll(UnaryOperator<E> operator) {
446 Objects.requireNonNull(operator);
447 final ListIterator<E> li = this.listIterator();
448 while (li.hasNext()) {
449 li.set(operator.apply(li.next()));
450 }
451 }
452
453 /**
454 * Sorts this list according to the order induced by the specified
455 * {@link Comparator}. The sort is <i>stable</i>: this method must not
456 * reorder equal elements.
457 *
458 * <p>All elements in this list must be <i>mutually comparable</i> using the
459 * specified comparator (that is, {@code c.compare(e1, e2)} must not throw
460 * a {@code ClassCastException} for any elements {@code e1} and {@code e2}
461 * in the list).
462 *
463 * <p>If the specified comparator is {@code null} then all elements in this
464 * list must implement the {@link Comparable} interface and the elements'
465 * {@linkplain Comparable natural ordering} should be used.
466 *
467 * <p>This list must be modifiable, but need not be resizable.
468 *
469 * @implSpec
470 * The default implementation obtains an array containing all elements in
471 * this list, sorts the array, and iterates over this list resetting each
472 * element from the corresponding position in the array. (This avoids the
473 * n<sup>2</sup> log(n) performance that would result from attempting
474 * to sort a linked list in place.)
475 *
476 * @implNote
477 * This implementation is a stable, adaptive, iterative mergesort that
478 * requires far fewer than n lg(n) comparisons when the input array is
479 * partially sorted, while offering the performance of a traditional
480 * mergesort when the input array is randomly ordered. If the input array
481 * is nearly sorted, the implementation requires approximately n
482 * comparisons. Temporary storage requirements vary from a small constant
483 * for nearly sorted input arrays to n/2 object references for randomly
484 * ordered input arrays.
485 *
486 * <p>The implementation takes equal advantage of ascending and
487 * descending order in its input array, and can take advantage of
488 * ascending and descending order in different parts of the same
489 * input array. It is well-suited to merging two or more sorted arrays:
490 * simply concatenate the arrays and sort the resulting array.
491 *
492 * <p>The implementation was adapted from Tim Peters's list sort for Python
493 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
494 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
495 * Sorting and Information Theoretic Complexity", in Proceedings of the
496 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
497 * January 1993.
498 *
499 * @param c the {@code Comparator} used to compare list elements.
500 * A {@code null} value indicates that the elements'
501 * {@linkplain Comparable natural ordering} should be used
502 * @throws ClassCastException if the list contains elements that are not
503 * <i>mutually comparable</i> using the specified comparator
504 * @throws UnsupportedOperationException if the list's list-iterator does
505 * not support the {@code set} operation
506 * @throws IllegalArgumentException
507 * (<a href="Collection.html#optional-restrictions">optional</a>)
508 * if the comparator is found to violate the {@link Comparator}
509 * contract
510 * @since 1.8
511 */
512 @SuppressWarnings({"unchecked", "rawtypes"})
513 default void sort(Comparator<? super E> c) {
514 Object[] a = this.toArray();
515 Arrays.sort(a, (Comparator) c);
516 ListIterator<E> i = this.listIterator();
517 for (Object e : a) {
518 i.next();
519 i.set((E) e);
520 }
521 }
522
523 /**
524 * Removes all of the elements from this list (optional operation).
525 * The list will be empty after this call returns.
526 *
527 * @throws UnsupportedOperationException if the {@code clear} operation
528 * is not supported by this list
529 */
530 void clear();
531
532
533 // Comparison and hashing
534
535 /**
536 * Compares the specified object with this list for equality. Returns
537 * {@code true} if and only if the specified object is also a list, both
538 * lists have the same size, and all corresponding pairs of elements in
539 * the two lists are <i>equal</i>. (Two elements {@code e1} and
540 * {@code e2} are <i>equal</i> if {@code (e1==null ? e2==null :
541 * e1.equals(e2))}.) In other words, two lists are defined to be
542 * equal if they contain the same elements in the same order. This
543 * definition ensures that the {@code equals} method works properly across
544 * different implementations of the {@code List} interface.
545 *
546 * @param o the object to be compared for equality with this list
547 * @return {@code true} if the specified object is equal to this list
548 */
549 boolean equals(Object o);
550
551 /**
552 * Returns the hash code value for this list. The hash code of a list
553 * is defined to be the result of the following calculation:
554 * <pre>{@code
555 * int hashCode = 1;
556 * for (E e : list)
557 * hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
558 * }</pre>
559 * This ensures that {@code list1.equals(list2)} implies that
560 * {@code list1.hashCode()==list2.hashCode()} for any two lists,
561 * {@code list1} and {@code list2}, as required by the general
562 * contract of {@link Object#hashCode}.
563 *
564 * @return the hash code value for this list
565 * @see Object#equals(Object)
566 * @see #equals(Object)
567 */
568 int hashCode();
569
570
571 // Positional Access Operations
572
573 /**
574 * Returns the element at the specified position in this list.
575 *
576 * @param index index of the element to return
577 * @return the element at the specified position in this list
578 * @throws IndexOutOfBoundsException if the index is out of range
579 * ({@code index < 0 || index >= size()})
580 */
581 E get(int index);
582
583 /**
584 * Replaces the element at the specified position in this list with the
585 * specified element (optional operation).
586 *
587 * @param index index of the element to replace
588 * @param element element to be stored at the specified position
589 * @return the element previously at the specified position
590 * @throws UnsupportedOperationException if the {@code set} operation
591 * is not supported by this list
592 * @throws ClassCastException if the class of the specified element
593 * prevents it from being added to this list
594 * @throws NullPointerException if the specified element is null and
595 * this list does not permit null elements
596 * @throws IllegalArgumentException if some property of the specified
597 * element prevents it from being added to this list
598 * @throws IndexOutOfBoundsException if the index is out of range
599 * ({@code index < 0 || index >= size()})
600 */
601 E set(int index, E element);
602
603 /**
604 * Inserts the specified element at the specified position in this list
605 * (optional operation). Shifts the element currently at that position
606 * (if any) and any subsequent elements to the right (adds one to their
607 * indices).
608 *
609 * @param index index at which the specified element is to be inserted
610 * @param element element to be inserted
611 * @throws UnsupportedOperationException if the {@code add} operation
612 * is not supported by this list
613 * @throws ClassCastException if the class of the specified element
614 * prevents it from being added to this list
615 * @throws NullPointerException if the specified element is null and
616 * this list does not permit null elements
617 * @throws IllegalArgumentException if some property of the specified
618 * element prevents it from being added to this list
619 * @throws IndexOutOfBoundsException if the index is out of range
620 * ({@code index < 0 || index > size()})
621 */
622 void add(int index, E element);
623
624 /**
625 * Removes the element at the specified position in this list (optional
626 * operation). Shifts any subsequent elements to the left (subtracts one
627 * from their indices). Returns the element that was removed from the
628 * list.
629 *
630 * @param index the index of the element to be removed
631 * @return the element previously at the specified position
632 * @throws UnsupportedOperationException if the {@code remove} operation
633 * is not supported by this list
634 * @throws IndexOutOfBoundsException if the index is out of range
635 * ({@code index < 0 || index >= size()})
636 */
637 E remove(int index);
638
639
640 // Search Operations
641
642 /**
643 * Returns the index of the first occurrence of the specified element
644 * in this list, or -1 if this list does not contain the element.
645 * More formally, returns the lowest index {@code i} such that
646 * {@code Objects.equals(o, get(i))},
647 * or -1 if there is no such index.
648 *
649 * @param o element to search for
650 * @return the index of the first occurrence of the specified element in
651 * this list, or -1 if this list does not contain the element
652 * @throws ClassCastException if the type of the specified element
653 * is incompatible with this list
654 * (<a href="Collection.html#optional-restrictions">optional</a>)
655 * @throws NullPointerException if the specified element is null and this
656 * list does not permit null elements
657 * (<a href="Collection.html#optional-restrictions">optional</a>)
658 */
659 int indexOf(Object o);
660
661 /**
662 * Returns the index of the last occurrence of the specified element
663 * in this list, or -1 if this list does not contain the element.
664 * More formally, returns the highest index {@code i} such that
665 * {@code Objects.equals(o, get(i))},
666 * or -1 if there is no such index.
667 *
668 * @param o element to search for
669 * @return the index of the last occurrence of the specified element in
670 * this list, or -1 if this list does not contain the element
671 * @throws ClassCastException if the type of the specified element
672 * is incompatible with this list
673 * (<a href="Collection.html#optional-restrictions">optional</a>)
674 * @throws NullPointerException if the specified element is null and this
675 * list does not permit null elements
676 * (<a href="Collection.html#optional-restrictions">optional</a>)
677 */
678 int lastIndexOf(Object o);
679
680
681 // List Iterators
682
683 /**
684 * Returns a list iterator over the elements in this list (in proper
685 * sequence).
686 *
687 * @return a list iterator over the elements in this list (in proper
688 * sequence)
689 */
690 ListIterator<E> listIterator();
691
692 /**
693 * Returns a list iterator over the elements in this list (in proper
694 * sequence), starting at the specified position in the list.
695 * The specified index indicates the first element that would be
696 * returned by an initial call to {@link ListIterator#next next}.
697 * An initial call to {@link ListIterator#previous previous} would
698 * return the element with the specified index minus one.
699 *
700 * @param index index of the first element to be returned from the
701 * list iterator (by a call to {@link ListIterator#next next})
702 * @return a list iterator over the elements in this list (in proper
703 * sequence), starting at the specified position in the list
704 * @throws IndexOutOfBoundsException if the index is out of range
705 * ({@code index < 0 || index > size()})
706 */
707 ListIterator<E> listIterator(int index);
708
709 // View
710
711 /**
712 * Returns a view of the portion of this list between the specified
713 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
714 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
715 * empty.) The returned list is backed by this list, so non-structural
716 * changes in the returned list are reflected in this list, and vice-versa.
717 * The returned list supports all of the optional list operations supported
718 * by this list.<p>
719 *
720 * This method eliminates the need for explicit range operations (of
721 * the sort that commonly exist for arrays). Any operation that expects
722 * a list can be used as a range operation by passing a subList view
723 * instead of a whole list. For example, the following idiom
724 * removes a range of elements from a list:
725 * <pre>{@code
726 * list.subList(from, to).clear();
727 * }</pre>
728 * Similar idioms may be constructed for {@code indexOf} and
729 * {@code lastIndexOf}, and all of the algorithms in the
730 * {@code Collections} class can be applied to a subList.<p>
731 *
732 * The semantics of the list returned by this method become undefined if
733 * the backing list (i.e., this list) is <i>structurally modified</i> in
734 * any way other than via the returned list. (Structural modifications are
735 * those that change the size of this list, or otherwise perturb it in such
736 * a fashion that iterations in progress may yield incorrect results.)
737 *
738 * @param fromIndex low endpoint (inclusive) of the subList
739 * @param toIndex high endpoint (exclusive) of the subList
740 * @return a view of the specified range within this list
741 * @throws IndexOutOfBoundsException for an illegal endpoint index value
742 * ({@code fromIndex < 0 || toIndex > size ||
743 * fromIndex > toIndex})
744 */
745 List<E> subList(int fromIndex, int toIndex);
746
747 /**
748 * Creates a {@link Spliterator} over the elements in this list.
749 *
750 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
751 * {@link Spliterator#ORDERED}. Implementations should document the
752 * reporting of additional characteristic values.
753 *
754 * @implSpec
755 * The default implementation creates a
756 * <em><a href="Spliterator.html#binding">late-binding</a></em>
757 * spliterator as follows:
758 * <ul>
759 * <li>If the list is an instance of {@link RandomAccess} then the default
760 * implementation creates a spliterator that traverses elements by
761 * invoking the method {@link List#get}. If such invocation results or
762 * would result in an {@code IndexOutOfBoundsException} then the
763 * spliterator will <em>fail-fast</em> and throw a
764 * {@code ConcurrentModificationException}.
765 * If the list is also an instance of {@link AbstractList} then the
766 * spliterator will use the list's {@link AbstractList#modCount modCount}
767 * field to provide additional <em>fail-fast</em> behavior.
768 * <li>Otherwise, the default implementation creates a spliterator from the
769 * list's {@code Iterator}. The spliterator inherits the
770 * <em>fail-fast</em> of the list's iterator.
771 * </ul>
772 *
773 * @implNote
774 * The created {@code Spliterator} additionally reports
775 * {@link Spliterator#SUBSIZED}.
776 *
777 * @return a {@code Spliterator} over the elements in this list
778 * @since 1.8
779 */
780 @Override
781 default Spliterator<E> spliterator() {
782 if (this instanceof RandomAccess) {
783 return new AbstractList.RandomAccessSpliterator<>(this);
784 } else {
785 return Spliterators.spliterator(this, Spliterator.ORDERED);
786 }
787 }
788
789 /**
790 * Returns an unmodifiable list containing zero elements.
791 *
792 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
793 *
794 * @param <E> the {@code List}'s element type
795 * @return an empty {@code List}
796 *
797 * @since 9
798 */
799 @SuppressWarnings("unchecked")
800 static <E> List<E> of() {
801 return (List<E>) ImmutableCollections.ListN.EMPTY_LIST;
802 }
803
804 /**
805 * Returns an unmodifiable list containing one element.
806 *
807 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
808 *
809 * @param <E> the {@code List}'s element type
810 * @param e1 the single element
811 * @return a {@code List} containing the specified element
812 * @throws NullPointerException if the element is {@code null}
813 *
814 * @since 9
815 */
816 static <E> List<E> of(E e1) {
817 return new ImmutableCollections.List12<>(e1);
818 }
819
820 /**
821 * Returns an unmodifiable list containing two elements.
822 *
823 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
824 *
825 * @param <E> the {@code List}'s element type
826 * @param e1 the first element
827 * @param e2 the second element
828 * @return a {@code List} containing the specified elements
829 * @throws NullPointerException if an element is {@code null}
830 *
831 * @since 9
832 */
833 static <E> List<E> of(E e1, E e2) {
834 return new ImmutableCollections.List12<>(e1, e2);
835 }
836
837 /**
838 * Returns an unmodifiable list containing three elements.
839 *
840 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
841 *
842 * @param <E> the {@code List}'s element type
843 * @param e1 the first element
844 * @param e2 the second element
845 * @param e3 the third element
846 * @return a {@code List} containing the specified elements
847 * @throws NullPointerException if an element is {@code null}
848 *
849 * @since 9
850 */
851 static <E> List<E> of(E e1, E e2, E e3) {
852 return new ImmutableCollections.ListN<>(e1, e2, e3);
853 }
854
855 /**
856 * Returns an unmodifiable list containing four elements.
857 *
858 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
859 *
860 * @param <E> the {@code List}'s element type
861 * @param e1 the first element
862 * @param e2 the second element
863 * @param e3 the third element
864 * @param e4 the fourth element
865 * @return a {@code List} containing the specified elements
866 * @throws NullPointerException if an element is {@code null}
867 *
868 * @since 9
869 */
870 static <E> List<E> of(E e1, E e2, E e3, E e4) {
871 return new ImmutableCollections.ListN<>(e1, e2, e3, e4);
872 }
873
874 /**
875 * Returns an unmodifiable list containing five elements.
876 *
877 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
878 *
879 * @param <E> the {@code List}'s element type
880 * @param e1 the first element
881 * @param e2 the second element
882 * @param e3 the third element
883 * @param e4 the fourth element
884 * @param e5 the fifth element
885 * @return a {@code List} containing the specified elements
886 * @throws NullPointerException if an element is {@code null}
887 *
888 * @since 9
889 */
890 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5) {
891 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5);
892 }
893
894 /**
895 * Returns an unmodifiable list containing six elements.
896 *
897 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
898 *
899 * @param <E> the {@code List}'s element type
900 * @param e1 the first element
901 * @param e2 the second element
902 * @param e3 the third element
903 * @param e4 the fourth element
904 * @param e5 the fifth element
905 * @param e6 the sixth element
906 * @return a {@code List} containing the specified elements
907 * @throws NullPointerException if an element is {@code null}
908 *
909 * @since 9
910 */
911 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
912 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
913 e6);
914 }
915
916 /**
917 * Returns an unmodifiable list containing seven elements.
918 *
919 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
920 *
921 * @param <E> the {@code List}'s element type
922 * @param e1 the first element
923 * @param e2 the second element
924 * @param e3 the third element
925 * @param e4 the fourth element
926 * @param e5 the fifth element
927 * @param e6 the sixth element
928 * @param e7 the seventh element
929 * @return a {@code List} containing the specified elements
930 * @throws NullPointerException if an element is {@code null}
931 *
932 * @since 9
933 */
934 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
935 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
936 e6, e7);
937 }
938
939 /**
940 * Returns an unmodifiable list containing eight elements.
941 *
942 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
943 *
944 * @param <E> the {@code List}'s element type
945 * @param e1 the first element
946 * @param e2 the second element
947 * @param e3 the third element
948 * @param e4 the fourth element
949 * @param e5 the fifth element
950 * @param e6 the sixth element
951 * @param e7 the seventh element
952 * @param e8 the eighth element
953 * @return a {@code List} containing the specified elements
954 * @throws NullPointerException if an element is {@code null}
955 *
956 * @since 9
957 */
958 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
959 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
960 e6, e7, e8);
961 }
962
963 /**
964 * Returns an unmodifiable list containing nine elements.
965 *
966 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
967 *
968 * @param <E> the {@code List}'s element type
969 * @param e1 the first element
970 * @param e2 the second element
971 * @param e3 the third element
972 * @param e4 the fourth element
973 * @param e5 the fifth element
974 * @param e6 the sixth element
975 * @param e7 the seventh element
976 * @param e8 the eighth element
977 * @param e9 the ninth element
978 * @return a {@code List} containing the specified elements
979 * @throws NullPointerException if an element is {@code null}
980 *
981 * @since 9
982 */
983 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
984 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
985 e6, e7, e8, e9);
986 }
987
988 /**
989 * Returns an unmodifiable list containing ten elements.
990 *
991 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
992 *
993 * @param <E> the {@code List}'s element type
994 * @param e1 the first element
995 * @param e2 the second element
996 * @param e3 the third element
997 * @param e4 the fourth element
998 * @param e5 the fifth element
999 * @param e6 the sixth element
1000 * @param e7 the seventh element
1001 * @param e8 the eighth element
1002 * @param e9 the ninth element
1003 * @param e10 the tenth element
1004 * @return a {@code List} containing the specified elements
1005 * @throws NullPointerException if an element is {@code null}
1006 *
1007 * @since 9
1008 */
1009 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) {
1010 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
1011 e6, e7, e8, e9, e10);
1012 }
1013
1014 /**
1015 * Returns an unmodifiable list containing an arbitrary number of elements.
1016 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
1017 *
1018 * @apiNote
1019 * This method also accepts a single array as an argument. The element type of
1020 * the resulting list will be the component type of the array, and the size of
1021 * the list will be equal to the length of the array. To create a list with
1022 * a single element that is an array, do the following:
1023 *
1024 * <pre>{@code
1025 * String[] array = ... ;
1026 * List<String[]> list = List.<String[]>of(array);
1027 * }</pre>
1028 *
1029 * This will cause the {@link List#of(Object) List.of(E)} method
1030 * to be invoked instead.
1031 *
1032 * @param <E> the {@code List}'s element type
1033 * @param elements the elements to be contained in the list
1034 * @return a {@code List} containing the specified elements
1035 * @throws NullPointerException if an element is {@code null} or if the array is {@code null}
1036 *
1037 * @since 9
1038 */
1039 @SafeVarargs
1040 @SuppressWarnings("varargs")
1041 static <E> List<E> of(E... elements) {
1042 switch (elements.length) { // implicit null check of elements
1043 case 0:
1044 @SuppressWarnings("unchecked")
1045 var list = (List<E>) ImmutableCollections.ListN.EMPTY_LIST;
1046 return list;
1047 case 1:
1048 return new ImmutableCollections.List12<>(elements[0]);
1049 case 2:
1050 return new ImmutableCollections.List12<>(elements[0], elements[1]);
1051 default:
1052 return new ImmutableCollections.ListN<>(elements);
1053 }
1054 }
1055
1056 /**
1057 * Returns an <a href="#unmodifiable">unmodifiable List</a> containing the elements of
1058 * the given Collection, in its iteration order. The given Collection must not be null,
1059 * and it must not contain any null elements. If the given Collection is subsequently
1060 * modified, the returned List will not reflect such modifications.
1061 *
1062 * @implNote
1063 * If the given Collection is an <a href="#unmodifiable">unmodifiable List</a>,
1064 * calling copyOf will generally not create a copy.
1065 *
1066 * @param <E> the {@code List}'s element type
1067 * @param coll a {@code Collection} from which elements are drawn, must be non-null
1068 * @return a {@code List} containing the elements of the given {@code Collection}
1069 * @throws NullPointerException if coll is null, or if it contains any nulls
1070 * @since 10
1071 */
1072 static <E> List<E> copyOf(Collection<? extends E> coll) {
1073 return ImmutableCollections.listCopy(coll);
1074 }
1075 }