1 /*
2 * Copyright (c) 1997, 2018, 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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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 *
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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
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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.
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}. The sort is <i>stable</i>: this method must not
447 * reorder equal elements.
448 *
449 * <p>All elements in this list must be <i>mutually comparable</i> using the
450 * specified comparator (that is, {@code c.compare(e1, e2)} must not throw
451 * a {@code ClassCastException} for any elements {@code e1} and {@code e2}
452 * in the list).
453 *
454 * <p>If the specified comparator is {@code null} then all elements in this
455 * list must implement the {@link Comparable} interface and the elements'
456 * {@linkplain Comparable natural ordering} should be used.
457 *
458 * <p>This list must be modifiable, but need not be resizable.
459 *
460 * @implSpec
461 * The default implementation obtains an array containing all elements in
462 * this list, sorts the array, and iterates over this list resetting each
463 * element from the corresponding position in the array. (This avoids the
464 * n<sup>2</sup> log(n) performance that would result from attempting
465 * to sort a linked list in place.)
466 *
467 * @implNote
468 * This implementation is a stable, adaptive, iterative mergesort that
469 * requires far fewer than n lg(n) comparisons when the input array is
470 * partially sorted, while offering the performance of a traditional
471 * mergesort when the input array is randomly ordered. If the input array
472 * is nearly sorted, the implementation requires approximately n
473 * comparisons. Temporary storage requirements vary from a small constant
474 * for nearly sorted input arrays to n/2 object references for randomly
475 * ordered input arrays.
476 *
477 * <p>The implementation takes equal advantage of ascending and
478 * descending order in its input array, and can take advantage of
479 * ascending and descending order in different parts of the same
480 * input array. It is well-suited to merging two or more sorted arrays:
481 * simply concatenate the arrays and sort the resulting array.
482 *
483 * <p>The implementation was adapted from Tim Peters's list sort for Python
484 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
485 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
486 * Sorting and Information Theoretic Complexity", in Proceedings of the
487 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
488 * January 1993.
489 *
490 * @param c the {@code Comparator} used to compare list elements.
491 * A {@code null} value indicates that the elements'
492 * {@linkplain Comparable natural ordering} should be used
493 * @throws ClassCastException if the list contains elements that are not
494 * <i>mutually comparable</i> using the specified comparator
495 * @throws UnsupportedOperationException if the list's list-iterator does
496 * not support the {@code set} operation
497 * @throws IllegalArgumentException
498 * (<a href="Collection.html#optional-restrictions">optional</a>)
499 * if the comparator is found to violate the {@link Comparator}
500 * contract
501 * @since 1.8
502 */
503 @SuppressWarnings({"unchecked", "rawtypes"})
504 default void sort(Comparator<? super E> c) {
505 Object[] a = this.toArray();
506 Arrays.sort(a, (Comparator) c);
507 ListIterator<E> i = this.listIterator();
508 for (Object e : a) {
509 i.next();
510 i.set((E) e);
511 }
512 }
513
514 /**
515 * Removes all of the elements from this list (optional operation).
516 * The list will be empty after this call returns.
517 *
518 * @throws UnsupportedOperationException if the {@code clear} operation
519 * is not supported by this list
520 */
521 void clear();
522
523
524 // Comparison and hashing
525
526 /**
527 * Compares the specified object with this list for equality. Returns
528 * {@code true} if and only if the specified object is also a list, both
529 * lists have the same size, and all corresponding pairs of elements in
530 * the two lists are <i>equal</i>. (Two elements {@code e1} and
531 * {@code e2} are <i>equal</i> if {@code Objects.equals(e1, e2)}.)
532 * In other words, two lists are defined to be
533 * equal if they contain the same elements in the same order. This
534 * definition ensures that the equals method works properly across
535 * different implementations of the {@code List} interface.
536 *
537 * @param o the object to be compared for equality with this list
538 * @return {@code true} if the specified object is equal to this list
539 */
540 boolean equals(Object o);
541
542 /**
543 * Returns the hash code value for this list. The hash code of a list
544 * is defined to be the result of the following calculation:
545 * <pre>{@code
546 * int hashCode = 1;
547 * for (E e : list)
548 * hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
549 * }</pre>
550 * This ensures that {@code list1.equals(list2)} implies that
551 * {@code list1.hashCode()==list2.hashCode()} for any two lists,
552 * {@code list1} and {@code list2}, as required by the general
553 * contract of {@link Object#hashCode}.
554 *
555 * @return the hash code value for this list
556 * @see Object#equals(Object)
557 * @see #equals(Object)
558 */
559 int hashCode();
560
561
562 // Positional Access Operations
563
564 /**
565 * Returns the element at the specified position in this list.
566 *
567 * @param index index of the element to return
568 * @return the element at the specified position in this list
569 * @throws IndexOutOfBoundsException if the index is out of range
570 * ({@code index < 0 || index >= size()})
571 */
572 E get(int index);
573
574 /**
575 * Replaces the element at the specified position in this list with the
576 * specified element (optional operation).
577 *
578 * @param index index of the element to replace
579 * @param element element to be stored at the specified position
580 * @return the element previously at the specified position
581 * @throws UnsupportedOperationException if the {@code set} operation
582 * is not supported by this list
583 * @throws ClassCastException if the class of the specified element
584 * prevents it from being added to this list
585 * @throws NullPointerException if the specified element is null and
586 * this list does not permit null elements
587 * @throws IllegalArgumentException if some property of the specified
588 * element prevents it from being added to this list
589 * @throws IndexOutOfBoundsException if the index is out of range
590 * ({@code index < 0 || index >= size()})
591 */
592 E set(int index, E element);
593
594 /**
595 * Inserts the specified element at the specified position in this list
596 * (optional operation). Shifts the element currently at that position
597 * (if any) and any subsequent elements to the right (adds one to their
598 * indices).
599 *
600 * @param index index at which the specified element is to be inserted
601 * @param element element to be inserted
602 * @throws UnsupportedOperationException if the {@code add} operation
603 * is not supported by this list
604 * @throws ClassCastException if the class of the specified element
605 * prevents it from being added to this list
606 * @throws NullPointerException if the specified element is null and
607 * this list does not permit null elements
608 * @throws IllegalArgumentException if some property of the specified
609 * element prevents it from being added to this list
610 * @throws IndexOutOfBoundsException if the index is out of range
611 * ({@code index < 0 || index > size()})
612 */
613 void add(int index, E element);
614
615 /**
616 * Removes the element at the specified position in this list (optional
617 * operation). Shifts any subsequent elements to the left (subtracts one
618 * from their indices). Returns the element that was removed from the
619 * list.
620 *
621 * @param index the index of the element to be removed
622 * @return the element previously at the specified position
623 * @throws UnsupportedOperationException if the {@code remove} operation
624 * is not supported by this list
625 * @throws IndexOutOfBoundsException if the index is out of range
626 * ({@code index < 0 || index >= size()})
627 */
628 E remove(int index);
629
630
631 // Search Operations
632
633 /**
634 * Returns the index of the first occurrence of the specified element
635 * in this list, or -1 if this list does not contain the element.
636 * More formally, returns the lowest index {@code i} such that
637 * {@code Objects.equals(o, get(i))},
638 * or -1 if there is no such index.
639 *
640 * @param o element to search for
641 * @return the index of the first occurrence of the specified element in
642 * this list, or -1 if this list does not contain the element
643 * @throws ClassCastException if the type of the specified element
644 * is incompatible with this list
645 * (<a href="Collection.html#optional-restrictions">optional</a>)
646 * @throws NullPointerException if the specified element is null and this
647 * list does not permit null elements
648 * (<a href="Collection.html#optional-restrictions">optional</a>)
649 */
650 int indexOf(Object o);
651
652 /**
653 * Returns the index of the last occurrence of the specified element
654 * in this list, or -1 if this list does not contain the element.
655 * More formally, returns the highest index {@code i} such that
656 * {@code Objects.equals(o, get(i))},
657 * or -1 if there is no such index.
658 *
659 * @param o element to search for
660 * @return the index of the last occurrence of the specified element in
661 * this list, or -1 if this list does not contain the element
662 * @throws ClassCastException if the type of the specified element
663 * is incompatible with this list
664 * (<a href="Collection.html#optional-restrictions">optional</a>)
665 * @throws NullPointerException if the specified element is null and this
666 * list does not permit null elements
667 * (<a href="Collection.html#optional-restrictions">optional</a>)
668 */
669 int lastIndexOf(Object o);
670
671
672 // List Iterators
673
674 /**
675 * Returns a list iterator over the elements in this list (in proper
676 * sequence).
677 *
678 * @return a list iterator over the elements in this list (in proper
679 * sequence)
680 */
681 ListIterator<E> listIterator();
682
683 /**
684 * Returns a list iterator over the elements in this list (in proper
685 * sequence), starting at the specified position in the list.
686 * The specified index indicates the first element that would be
687 * returned by an initial call to {@link ListIterator#next next}.
688 * An initial call to {@link ListIterator#previous previous} would
689 * return the element with the specified index minus one.
690 *
691 * @param index index of the first element to be returned from the
692 * list iterator (by a call to {@link ListIterator#next next})
693 * @return a list iterator over the elements in this list (in proper
694 * sequence), starting at the specified position in the list
695 * @throws IndexOutOfBoundsException if the index is out of range
696 * ({@code index < 0 || index > size()})
697 */
698 ListIterator<E> listIterator(int index);
699
700 // View
701
702 /**
703 * Returns a view of the portion of this list between the specified
704 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
705 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
706 * empty.) The returned list is backed by this list, so non-structural
707 * changes in the returned list are reflected in this list, and vice-versa.
708 * The returned list supports all of the optional list operations supported
709 * by this list.<p>
710 *
711 * This method eliminates the need for explicit range operations (of
712 * the sort that commonly exist for arrays). Any operation that expects
713 * a list can be used as a range operation by passing a subList view
714 * instead of a whole list. For example, the following idiom
715 * removes a range of elements from a list:
716 * <pre>{@code
717 * list.subList(from, to).clear();
718 * }</pre>
719 * Similar idioms may be constructed for {@code indexOf} and
720 * {@code lastIndexOf}, and all of the algorithms in the
721 * {@code Collections} class can be applied to a subList.<p>
722 *
723 * The semantics of the list returned by this method become undefined if
724 * the backing list (i.e., this list) is <i>structurally modified</i> in
725 * any way other than via the returned list. (Structural modifications are
726 * those that change the size of this list, or otherwise perturb it in such
727 * a fashion that iterations in progress may yield incorrect results.)
728 *
729 * @param fromIndex low endpoint (inclusive) of the subList
730 * @param toIndex high endpoint (exclusive) of the subList
731 * @return a view of the specified range within this list
732 * @throws IndexOutOfBoundsException for an illegal endpoint index value
733 * ({@code fromIndex < 0 || toIndex > size ||
734 * fromIndex > toIndex})
735 */
736 List<E> subList(int fromIndex, int toIndex);
737
738 /**
739 * Creates a {@link Spliterator} over the elements in this list.
740 *
741 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
742 * {@link Spliterator#ORDERED}. Implementations should document the
743 * reporting of additional characteristic values.
744 *
745 * @implSpec
746 * The default implementation creates a
747 * <em><a href="Spliterator.html#binding">late-binding</a></em>
748 * spliterator as follows:
749 * <ul>
750 * <li>If the list is an instance of {@link RandomAccess} then the default
751 * implementation creates a spliterator that traverses elements by
752 * invoking the method {@link List#get}. If such invocation results or
753 * would result in an {@code IndexOutOfBoundsException} then the
754 * spliterator will <em>fail-fast</em> and throw a
755 * {@code ConcurrentModificationException}.
756 * If the list is also an instance of {@link AbstractList} then the
757 * spliterator will use the list's {@link AbstractList#modCount modCount}
758 * field to provide additional <em>fail-fast</em> behavior.
759 * <li>Otherwise, the default implementation creates a spliterator from the
760 * list's {@code Iterator}. The spliterator inherits the
761 * <em>fail-fast</em> of the list's iterator.
762 * </ul>
763 *
764 * @implNote
765 * The created {@code Spliterator} additionally reports
766 * {@link Spliterator#SUBSIZED}.
767 *
768 * @return a {@code Spliterator} over the elements in this list
769 * @since 1.8
770 */
771 @Override
772 default Spliterator<E> spliterator() {
773 if (this instanceof RandomAccess) {
774 return new AbstractList.RandomAccessSpliterator<>(this);
775 } else {
776 return Spliterators.spliterator(this, Spliterator.ORDERED);
777 }
778 }
779
780 /**
781 * Returns an unmodifiable list containing zero elements.
782 *
783 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
784 *
785 * @param <E> the {@code List}'s element type
786 * @return an empty {@code List}
787 *
788 * @since 9
789 */
790 @SuppressWarnings("unchecked")
791 static <E> List<E> of() {
792 return (List<E>) ImmutableCollections.ListN.EMPTY_LIST;
793 }
794
795 /**
796 * Returns an unmodifiable list containing one element.
797 *
798 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
799 *
800 * @param <E> the {@code List}'s element type
801 * @param e1 the single element
802 * @return a {@code List} containing the specified element
803 * @throws NullPointerException if the element is {@code null}
804 *
805 * @since 9
806 */
807 static <E> List<E> of(E e1) {
808 return new ImmutableCollections.List12<>(e1);
809 }
810
811 /**
812 * Returns an unmodifiable list containing two elements.
813 *
814 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
815 *
816 * @param <E> the {@code List}'s element type
817 * @param e1 the first element
818 * @param e2 the second element
819 * @return a {@code List} containing the specified elements
820 * @throws NullPointerException if an element is {@code null}
821 *
822 * @since 9
823 */
824 static <E> List<E> of(E e1, E e2) {
825 return new ImmutableCollections.List12<>(e1, e2);
826 }
827
828 /**
829 * Returns an unmodifiable list containing three elements.
830 *
831 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
832 *
833 * @param <E> the {@code List}'s element type
834 * @param e1 the first element
835 * @param e2 the second element
836 * @param e3 the third element
837 * @return a {@code List} containing the specified elements
838 * @throws NullPointerException if an element is {@code null}
839 *
840 * @since 9
841 */
842 static <E> List<E> of(E e1, E e2, E e3) {
843 return new ImmutableCollections.ListN<>(e1, e2, e3);
844 }
845
846 /**
847 * Returns an unmodifiable list containing four elements.
848 *
849 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
850 *
851 * @param <E> the {@code List}'s element type
852 * @param e1 the first element
853 * @param e2 the second element
854 * @param e3 the third element
855 * @param e4 the fourth element
856 * @return a {@code List} containing the specified elements
857 * @throws NullPointerException if an element is {@code null}
858 *
859 * @since 9
860 */
861 static <E> List<E> of(E e1, E e2, E e3, E e4) {
862 return new ImmutableCollections.ListN<>(e1, e2, e3, e4);
863 }
864
865 /**
866 * Returns an unmodifiable list containing five elements.
867 *
868 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
869 *
870 * @param <E> the {@code List}'s element type
871 * @param e1 the first element
872 * @param e2 the second element
873 * @param e3 the third element
874 * @param e4 the fourth element
875 * @param e5 the fifth element
876 * @return a {@code List} containing the specified elements
877 * @throws NullPointerException if an element is {@code null}
878 *
879 * @since 9
880 */
881 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5) {
882 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5);
883 }
884
885 /**
886 * Returns an unmodifiable list containing six elements.
887 *
888 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
889 *
890 * @param <E> the {@code List}'s element type
891 * @param e1 the first element
892 * @param e2 the second element
893 * @param e3 the third element
894 * @param e4 the fourth element
895 * @param e5 the fifth element
896 * @param e6 the sixth element
897 * @return a {@code List} containing the specified elements
898 * @throws NullPointerException if an element is {@code null}
899 *
900 * @since 9
901 */
902 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
903 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
904 e6);
905 }
906
907 /**
908 * Returns an unmodifiable list containing seven elements.
909 *
910 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
911 *
912 * @param <E> the {@code List}'s element type
913 * @param e1 the first element
914 * @param e2 the second element
915 * @param e3 the third element
916 * @param e4 the fourth element
917 * @param e5 the fifth element
918 * @param e6 the sixth element
919 * @param e7 the seventh element
920 * @return a {@code List} containing the specified elements
921 * @throws NullPointerException if an element is {@code null}
922 *
923 * @since 9
924 */
925 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
926 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
927 e6, e7);
928 }
929
930 /**
931 * Returns an unmodifiable list containing eight elements.
932 *
933 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
934 *
935 * @param <E> the {@code List}'s element type
936 * @param e1 the first element
937 * @param e2 the second element
938 * @param e3 the third element
939 * @param e4 the fourth element
940 * @param e5 the fifth element
941 * @param e6 the sixth element
942 * @param e7 the seventh element
943 * @param e8 the eighth element
944 * @return a {@code List} containing the specified elements
945 * @throws NullPointerException if an element is {@code null}
946 *
947 * @since 9
948 */
949 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
950 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
951 e6, e7, e8);
952 }
953
954 /**
955 * Returns an unmodifiable list containing nine elements.
956 *
957 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
958 *
959 * @param <E> the {@code List}'s element type
960 * @param e1 the first element
961 * @param e2 the second element
962 * @param e3 the third element
963 * @param e4 the fourth element
964 * @param e5 the fifth element
965 * @param e6 the sixth element
966 * @param e7 the seventh element
967 * @param e8 the eighth element
968 * @param e9 the ninth element
969 * @return a {@code List} containing the specified elements
970 * @throws NullPointerException if an element is {@code null}
971 *
972 * @since 9
973 */
974 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
975 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
976 e6, e7, e8, e9);
977 }
978
979 /**
980 * Returns an unmodifiable list containing ten elements.
981 *
982 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
983 *
984 * @param <E> the {@code List}'s element type
985 * @param e1 the first element
986 * @param e2 the second element
987 * @param e3 the third element
988 * @param e4 the fourth element
989 * @param e5 the fifth element
990 * @param e6 the sixth element
991 * @param e7 the seventh element
992 * @param e8 the eighth element
993 * @param e9 the ninth element
994 * @param e10 the tenth element
995 * @return a {@code List} containing the specified elements
996 * @throws NullPointerException if an element is {@code null}
997 *
998 * @since 9
999 */
1000 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) {
1001 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
1002 e6, e7, e8, e9, e10);
1003 }
1004
1005 /**
1006 * Returns an unmodifiable list containing an arbitrary number of elements.
1007 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
1008 *
1009 * @apiNote
1010 * This method also accepts a single array as an argument. The element type of
1011 * the resulting list will be the component type of the array, and the size of
1012 * the list will be equal to the length of the array. To create a list with
1013 * a single element that is an array, do the following:
1014 *
1015 * <pre>{@code
1016 * String[] array = ... ;
1017 * List<String[]> list = List.<String[]>of(array);
1018 * }</pre>
1019 *
1020 * This will cause the {@link List#of(Object) List.of(E)} method
1021 * to be invoked instead.
1022 *
1023 * @param <E> the {@code List}'s element type
1024 * @param elements the elements to be contained in the list
1025 * @return a {@code List} containing the specified elements
1026 * @throws NullPointerException if an element is {@code null} or if the array is {@code null}
1027 *
1028 * @since 9
1029 */
1030 @SafeVarargs
1031 @SuppressWarnings("varargs")
1032 static <E> List<E> of(E... elements) {
1033 switch (elements.length) { // implicit null check of elements
1034 case 0:
1035 @SuppressWarnings("unchecked")
1036 var list = (List<E>) ImmutableCollections.ListN.EMPTY_LIST;
1037 return list;
1038 case 1:
1039 return new ImmutableCollections.List12<>(elements[0]);
1040 case 2:
1041 return new ImmutableCollections.List12<>(elements[0], elements[1]);
1042 default:
1043 return new ImmutableCollections.ListN<>(elements);
1044 }
1045 }
1046
1047 /**
1048 * Returns an <a href="#unmodifiable">unmodifiable List</a> containing the elements of
1049 * the given Collection, in its iteration order. The given Collection must not be null,
1050 * and it must not contain any null elements. If the given Collection is subsequently
1051 * modified, the returned List will not reflect such modifications.
1052 *
1053 * @implNote
1054 * If the given Collection is an <a href="#unmodifiable">unmodifiable List</a>,
1055 * calling copyOf will generally not create a copy.
1056 *
1057 * @param <E> the {@code List}'s element type
1058 * @param coll a {@code Collection} from which elements are drawn, must be non-null
1059 * @return a {@code List} containing the elements of the given {@code Collection}
1060 * @throws NullPointerException if coll is null, or if it contains any nulls
1061 * @since 10
1062 */
1063 static <E> List<E> copyOf(Collection<? extends E> coll) {
1064 return ImmutableCollections.listCopy(coll);
1065 }
1066 }