1 /*
2 * Copyright (c) 1997, 2017, 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
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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/util/package-summary.html#CollectionsFramework">
119 * Java Collections Framework</a>.
120 *
121 * @param <E> the type of elements in this list
122 *
123 * @author Josh Bloch
124 * @author Neal Gafter
125 * @see Collection
126 * @see Set
127 * @see ArrayList
128 * @see LinkedList
129 * @see Vector
130 * @see Arrays#asList(Object[])
131 * @see Collections#nCopies(int, Object)
132 * @see Collections#EMPTY_LIST
133 * @see AbstractList
134 * @see AbstractSequentialList
135 * @since 1.2
136 */
137
138 public interface List<E> extends Collection<E> {
139 // Query Operations
140
141 /**
142 * Returns the number of elements in this list. If this list contains
143 * more than {@code Integer.MAX_VALUE} elements, returns
144 * {@code Integer.MAX_VALUE}.
145 *
146 * @return the number of elements in this list
147 */
148 int size();
149
150 /**
151 * Returns {@code true} if this list contains no elements.
152 *
153 * @return {@code true} if this list contains no elements
154 */
155 boolean isEmpty();
156
157 /**
158 * Returns {@code true} if this list contains the specified element.
159 * More formally, returns {@code true} if and only if this list contains
160 * at least one element {@code e} such that
161 * {@code Objects.equals(o, e)}.
162 *
163 * @param o element whose presence in this list is to be tested
164 * @return {@code true} if this list contains the specified element
165 * @throws ClassCastException if the type of the specified element
166 * is incompatible with this list
167 * (<a href="Collection.html#optional-restrictions">optional</a>)
168 * @throws NullPointerException if the specified element is null and this
169 * list does not permit null elements
170 * (<a href="Collection.html#optional-restrictions">optional</a>)
171 */
172 boolean contains(Object o);
173
174 /**
175 * Returns an iterator over the elements in this list in proper sequence.
176 *
177 * @return an iterator over the elements in this list in proper sequence
178 */
179 Iterator<E> iterator();
180
181 /**
182 * Returns an array containing all of the elements in this list in proper
183 * sequence (from first to last element).
184 *
185 * <p>The returned array will be "safe" in that no references to it are
186 * maintained by this list. (In other words, this method must
187 * allocate a new array even if this list is backed by an array).
188 * The caller is thus free to modify the returned array.
189 *
190 * <p>This method acts as bridge between array-based and collection-based
191 * APIs.
192 *
193 * @return an array containing all of the elements in this list in proper
194 * sequence
195 * @see Arrays#asList(Object[])
196 */
197 Object[] toArray();
198
199 /**
200 * Returns an array containing all of the elements in this list in
201 * proper sequence (from first to last element); the runtime type of
202 * the returned array is that of the specified array. If the list fits
203 * in the specified array, it is returned therein. Otherwise, a new
204 * array is allocated with the runtime type of the specified array and
205 * the size of this list.
206 *
207 * <p>If the list fits in the specified array with room to spare (i.e.,
208 * the array has more elements than the list), the element in the array
209 * immediately following the end of the list is set to {@code null}.
210 * (This is useful in determining the length of the list <i>only</i> if
211 * the caller knows that the list does not contain any null elements.)
212 *
213 * <p>Like the {@link #toArray()} method, this method acts as bridge between
214 * array-based and collection-based APIs. Further, this method allows
215 * precise control over the runtime type of the output array, and may,
216 * under certain circumstances, be used to save allocation costs.
217 *
218 * <p>Suppose {@code x} is a list known to contain only strings.
219 * The following code can be used to dump the list into a newly
220 * allocated array of {@code String}:
221 *
222 * <pre>{@code
223 * String[] y = x.toArray(new String[0]);
224 * }</pre>
225 *
226 * Note that {@code toArray(new Object[0])} is identical in function to
227 * {@code toArray()}.
228 *
229 * @param a the array into which the elements of this list are to
230 * be stored, if it is big enough; otherwise, a new array of the
231 * same runtime type is allocated for this purpose.
232 * @return an array containing the elements of this list
233 * @throws ArrayStoreException if the runtime type of the specified array
234 * is not a supertype of the runtime type of every element in
235 * this list
236 * @throws NullPointerException if the specified array is null
237 */
238 <T> T[] toArray(T[] a);
239
240
241 // Modification Operations
242
243 /**
244 * Appends the specified element to the end of this list (optional
245 * operation).
246 *
247 * <p>Lists that support this operation may place limitations on what
248 * elements may be added to this list. In particular, some
249 * lists will refuse to add null elements, and others will impose
250 * restrictions on the type of elements that may be added. List
251 * classes should clearly specify in their documentation any restrictions
252 * on what elements may be added.
253 *
254 * @param e element to be appended to this list
255 * @return {@code true} (as specified by {@link Collection#add})
256 * @throws UnsupportedOperationException if the {@code add} operation
257 * is not supported by this list
258 * @throws ClassCastException if the class of the specified element
259 * prevents it from being added to this list
260 * @throws NullPointerException if the specified element is null and this
261 * list does not permit null elements
262 * @throws IllegalArgumentException if some property of this element
263 * prevents it from being added to this list
264 */
265 boolean add(E e);
266
267 /**
268 * Removes the first occurrence of the specified element from this list,
269 * if it is present (optional operation). If this list does not contain
270 * the element, it is unchanged. More formally, removes the element with
271 * the lowest index {@code i} such that
272 * {@code Objects.equals(o, get(i))}
273 * (if such an element exists). Returns {@code true} if this list
274 * contained the specified element (or equivalently, if this list changed
275 * as a result of the call).
276 *
277 * @param o element to be removed from this list, if present
278 * @return {@code true} if this list contained the specified element
279 * @throws ClassCastException if the type of the specified element
280 * is incompatible with this list
281 * (<a href="Collection.html#optional-restrictions">optional</a>)
282 * @throws NullPointerException if the specified element is null and this
283 * list does not permit null elements
284 * (<a href="Collection.html#optional-restrictions">optional</a>)
285 * @throws UnsupportedOperationException if the {@code remove} operation
286 * is not supported by this list
287 */
288 boolean remove(Object o);
289
290
291 // Bulk Modification Operations
292
293 /**
294 * Returns {@code true} if this list contains all of the elements of the
295 * specified collection.
296 *
297 * @param c collection to be checked for containment in this list
298 * @return {@code true} if this list contains all of the elements of the
299 * specified collection
300 * @throws ClassCastException if the types of one or more elements
301 * in the specified collection are incompatible with this
302 * list
303 * (<a href="Collection.html#optional-restrictions">optional</a>)
304 * @throws NullPointerException if the specified collection contains one
305 * or more null elements and this list does not permit null
306 * elements
307 * (<a href="Collection.html#optional-restrictions">optional</a>),
308 * or if the specified collection is null
309 * @see #contains(Object)
310 */
311 boolean containsAll(Collection<?> c);
312
313 /**
314 * Appends all of the elements in the specified collection to the end of
315 * this list, in the order that they are returned by the specified
316 * collection's iterator (optional operation). The behavior of this
317 * operation is undefined if the specified collection is modified while
318 * the operation is in progress. (Note that this will occur if the
319 * specified collection is this list, and it's nonempty.)
320 *
321 * @param c collection containing elements to be added to this list
322 * @return {@code true} if this list changed as a result of the call
323 * @throws UnsupportedOperationException if the {@code addAll} operation
324 * is not supported by this list
325 * @throws ClassCastException if the class of an element of the specified
326 * collection prevents it from being added to this list
327 * @throws NullPointerException if the specified collection contains one
328 * or more null elements and this list does not permit null
329 * elements, or if the specified collection is null
330 * @throws IllegalArgumentException if some property of an element of the
331 * specified collection prevents it from being added to this list
332 * @see #add(Object)
333 */
334 boolean addAll(Collection<? extends E> c);
335
336 /**
337 * Inserts all of the elements in the specified collection into this
338 * list at the specified position (optional operation). Shifts the
339 * element currently at that position (if any) and any subsequent
340 * elements to the right (increases their indices). The new elements
341 * will appear in this list in the order that they are returned by the
342 * specified collection's iterator. The behavior of this operation is
343 * undefined if the specified collection is modified while the
344 * operation is in progress. (Note that this will occur if the specified
345 * collection is this list, and it's nonempty.)
346 *
347 * @param index index at which to insert the first element from the
348 * specified collection
349 * @param c collection containing elements to be added to this list
350 * @return {@code true} if this list changed as a result of the call
351 * @throws UnsupportedOperationException if the {@code addAll} operation
352 * is not supported by this list
353 * @throws ClassCastException if the class of an element of the specified
354 * collection prevents it from being added to this list
355 * @throws NullPointerException if the specified collection contains one
356 * or more null elements and this list does not permit null
357 * elements, or if the specified collection is null
358 * @throws IllegalArgumentException if some property of an element of the
359 * specified collection prevents it from being added to this list
360 * @throws IndexOutOfBoundsException if the index is out of range
361 * ({@code index < 0 || index > size()})
362 */
363 boolean addAll(int index, Collection<? extends E> c);
364
365 /**
366 * Removes from this list all of its elements that are contained in the
367 * specified collection (optional operation).
368 *
369 * @param c collection containing elements to be removed from this list
370 * @return {@code true} if this list changed as a result of the call
371 * @throws UnsupportedOperationException if the {@code removeAll} operation
372 * is not supported by this list
373 * @throws ClassCastException if the class of an element of this list
374 * is incompatible with the specified collection
375 * (<a href="Collection.html#optional-restrictions">optional</a>)
376 * @throws NullPointerException if this list contains a null element and the
377 * specified collection does not permit null elements
378 * (<a href="Collection.html#optional-restrictions">optional</a>),
379 * or if the specified collection is null
380 * @see #remove(Object)
381 * @see #contains(Object)
382 */
383 boolean removeAll(Collection<?> c);
384
385 /**
386 * Retains only the elements in this list that are contained in the
387 * specified collection (optional operation). In other words, removes
388 * from this list all of its elements that are not contained in the
389 * specified collection.
390 *
391 * @param c collection containing elements to be retained in this list
392 * @return {@code true} if this list changed as a result of the call
393 * @throws UnsupportedOperationException if the {@code retainAll} operation
394 * is not supported by this list
395 * @throws ClassCastException if the class of an element of this list
396 * is incompatible with the specified collection
397 * (<a href="Collection.html#optional-restrictions">optional</a>)
398 * @throws NullPointerException if this list contains a null element and the
399 * specified collection does not permit null elements
400 * (<a href="Collection.html#optional-restrictions">optional</a>),
401 * or if the specified collection is null
402 * @see #remove(Object)
403 * @see #contains(Object)
404 */
405 boolean retainAll(Collection<?> c);
406
407 /**
408 * Replaces each element of this list with the result of applying the
409 * operator to that element. Errors or runtime exceptions thrown by
410 * the operator are relayed to the caller.
411 *
412 * @implSpec
413 * The default implementation is equivalent to, for this {@code list}:
414 * <pre>{@code
415 * final ListIterator<E> li = list.listIterator();
416 * while (li.hasNext()) {
417 * li.set(operator.apply(li.next()));
418 * }
419 * }</pre>
420 *
421 * If the list's list-iterator does not support the {@code set} operation
422 * then an {@code UnsupportedOperationException} will be thrown when
423 * replacing the first element.
424 *
425 * @param operator the operator to apply to each element
426 * @throws UnsupportedOperationException if this list is unmodifiable.
427 * Implementations may throw this exception if an element
428 * cannot be replaced or if, in general, modification is not
429 * supported
430 * @throws NullPointerException if the specified operator is null or
431 * if the operator result is a null value and this list does
432 * not permit null elements
433 * (<a href="Collection.html#optional-restrictions">optional</a>)
434 * @since 1.8
435 */
436 default void replaceAll(UnaryOperator<E> operator) {
437 Objects.requireNonNull(operator);
438 final ListIterator<E> li = this.listIterator();
439 while (li.hasNext()) {
440 li.set(operator.apply(li.next()));
441 }
442 }
443
444 /**
445 * Sorts this list according to the order induced by the specified
446 * {@link Comparator}.
447 *
448 * <p>All elements in this list must be <i>mutually comparable</i> using the
449 * specified comparator (that is, {@code c.compare(e1, e2)} must not throw
450 * a {@code ClassCastException} for any elements {@code e1} and {@code e2}
451 * in the list).
452 *
453 * <p>If the specified comparator is {@code null} then all elements in this
454 * list must implement the {@link Comparable} interface and the elements'
455 * {@linkplain Comparable natural ordering} should be used.
456 *
457 * <p>This list must be modifiable, but need not be resizable.
458 *
459 * @implSpec
460 * The default implementation obtains an array containing all elements in
461 * this list, sorts the array, and iterates over this list resetting each
462 * element from the corresponding position in the array. (This avoids the
463 * n<sup>2</sup> log(n) performance that would result from attempting
464 * to sort a linked list in place.)
465 *
466 * @implNote
467 * This implementation is a stable, adaptive, iterative mergesort that
468 * requires far fewer than n lg(n) comparisons when the input array is
469 * partially sorted, while offering the performance of a traditional
470 * mergesort when the input array is randomly ordered. If the input array
471 * is nearly sorted, the implementation requires approximately n
472 * comparisons. Temporary storage requirements vary from a small constant
473 * for nearly sorted input arrays to n/2 object references for randomly
474 * ordered input arrays.
475 *
476 * <p>The implementation takes equal advantage of ascending and
477 * descending order in its input array, and can take advantage of
478 * ascending and descending order in different parts of the same
479 * input array. It is well-suited to merging two or more sorted arrays:
480 * simply concatenate the arrays and sort the resulting array.
481 *
482 * <p>The implementation was adapted from Tim Peters's list sort for Python
483 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
484 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
485 * Sorting and Information Theoretic Complexity", in Proceedings of the
486 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
487 * January 1993.
488 *
489 * @param c the {@code Comparator} used to compare list elements.
490 * A {@code null} value indicates that the elements'
491 * {@linkplain Comparable natural ordering} should be used
492 * @throws ClassCastException if the list contains elements that are not
493 * <i>mutually comparable</i> using the specified comparator
494 * @throws UnsupportedOperationException if the list's list-iterator does
495 * not support the {@code set} operation
496 * @throws IllegalArgumentException
497 * (<a href="Collection.html#optional-restrictions">optional</a>)
498 * if the comparator is found to violate the {@link Comparator}
499 * contract
500 * @since 1.8
501 */
502 @SuppressWarnings({"unchecked", "rawtypes"})
503 default void sort(Comparator<? super E> c) {
504 Object[] a = this.toArray();
505 Arrays.sort(a, (Comparator) c);
506 ListIterator<E> i = this.listIterator();
507 for (Object e : a) {
508 i.next();
509 i.set((E) e);
510 }
511 }
512
513 /**
514 * Removes all of the elements from this list (optional operation).
515 * The list will be empty after this call returns.
516 *
517 * @throws UnsupportedOperationException if the {@code clear} operation
518 * is not supported by this list
519 */
520 void clear();
521
522
523 // Comparison and hashing
524
525 /**
526 * Compares the specified object with this list for equality. Returns
527 * {@code true} if and only if the specified object is also a list, both
528 * lists have the same size, and all corresponding pairs of elements in
529 * the two lists are <i>equal</i>. (Two elements {@code e1} and
530 * {@code e2} are <i>equal</i> if {@code Objects.equals(e1, e2)}.)
531 * In other words, two lists are defined to be
532 * equal if they contain the same elements in the same order. This
533 * definition ensures that the equals method works properly across
534 * different implementations of the {@code List} interface.
535 *
536 * @param o the object to be compared for equality with this list
537 * @return {@code true} if the specified object is equal to this list
538 */
539 boolean equals(Object o);
540
541 /**
542 * Returns the hash code value for this list. The hash code of a list
543 * is defined to be the result of the following calculation:
544 * <pre>{@code
545 * int hashCode = 1;
546 * for (E e : list)
547 * hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
548 * }</pre>
549 * This ensures that {@code list1.equals(list2)} implies that
550 * {@code list1.hashCode()==list2.hashCode()} for any two lists,
551 * {@code list1} and {@code list2}, as required by the general
552 * contract of {@link Object#hashCode}.
553 *
554 * @return the hash code value for this list
555 * @see Object#equals(Object)
556 * @see #equals(Object)
557 */
558 int hashCode();
559
560
561 // Positional Access Operations
562
563 /**
564 * Returns the element at the specified position in this list.
565 *
566 * @param index index of the element to return
567 * @return the element at the specified position in this list
568 * @throws IndexOutOfBoundsException if the index is out of range
569 * ({@code index < 0 || index >= size()})
570 */
571 E get(int index);
572
573 /**
574 * Replaces the element at the specified position in this list with the
575 * specified element (optional operation).
576 *
577 * @param index index of the element to replace
578 * @param element element to be stored at the specified position
579 * @return the element previously at the specified position
580 * @throws UnsupportedOperationException if the {@code set} operation
581 * is not supported by this list
582 * @throws ClassCastException if the class of the specified element
583 * prevents it from being added to this list
584 * @throws NullPointerException if the specified element is null and
585 * this list does not permit null elements
586 * @throws IllegalArgumentException if some property of the specified
587 * element prevents it from being added to this list
588 * @throws IndexOutOfBoundsException if the index is out of range
589 * ({@code index < 0 || index >= size()})
590 */
591 E set(int index, E element);
592
593 /**
594 * Inserts the specified element at the specified position in this list
595 * (optional operation). Shifts the element currently at that position
596 * (if any) and any subsequent elements to the right (adds one to their
597 * indices).
598 *
599 * @param index index at which the specified element is to be inserted
600 * @param element element to be inserted
601 * @throws UnsupportedOperationException if the {@code add} operation
602 * is not supported by this list
603 * @throws ClassCastException if the class of the specified element
604 * prevents it from being added to this list
605 * @throws NullPointerException if the specified element is null and
606 * this list does not permit null elements
607 * @throws IllegalArgumentException if some property of the specified
608 * element prevents it from being added to this list
609 * @throws IndexOutOfBoundsException if the index is out of range
610 * ({@code index < 0 || index > size()})
611 */
612 void add(int index, E element);
613
614 /**
615 * Removes the element at the specified position in this list (optional
616 * operation). Shifts any subsequent elements to the left (subtracts one
617 * from their indices). Returns the element that was removed from the
618 * list.
619 *
620 * @param index the index of the element to be removed
621 * @return the element previously at the specified position
622 * @throws UnsupportedOperationException if the {@code remove} operation
623 * is not supported by this list
624 * @throws IndexOutOfBoundsException if the index is out of range
625 * ({@code index < 0 || index >= size()})
626 */
627 E remove(int index);
628
629
630 // Search Operations
631
632 /**
633 * Returns the index of the first occurrence of the specified element
634 * in this list, or -1 if this list does not contain the element.
635 * More formally, returns the lowest index {@code i} such that
636 * {@code Objects.equals(o, get(i))},
637 * or -1 if there is no such index.
638 *
639 * @param o element to search for
640 * @return the index of the first occurrence of the specified element in
641 * this list, or -1 if this list does not contain the element
642 * @throws ClassCastException if the type of the specified element
643 * is incompatible with this list
644 * (<a href="Collection.html#optional-restrictions">optional</a>)
645 * @throws NullPointerException if the specified element is null and this
646 * list does not permit null elements
647 * (<a href="Collection.html#optional-restrictions">optional</a>)
648 */
649 int indexOf(Object o);
650
651 /**
652 * Returns the index of the last occurrence of the specified element
653 * in this list, or -1 if this list does not contain the element.
654 * More formally, returns the highest index {@code i} such that
655 * {@code Objects.equals(o, get(i))},
656 * or -1 if there is no such index.
657 *
658 * @param o element to search for
659 * @return the index of the last occurrence of the specified element in
660 * this list, or -1 if this list does not contain the element
661 * @throws ClassCastException if the type of the specified element
662 * is incompatible with this list
663 * (<a href="Collection.html#optional-restrictions">optional</a>)
664 * @throws NullPointerException if the specified element is null and this
665 * list does not permit null elements
666 * (<a href="Collection.html#optional-restrictions">optional</a>)
667 */
668 int lastIndexOf(Object o);
669
670
671 // List Iterators
672
673 /**
674 * Returns a list iterator over the elements in this list (in proper
675 * sequence).
676 *
677 * @return a list iterator over the elements in this list (in proper
678 * sequence)
679 */
680 ListIterator<E> listIterator();
681
682 /**
683 * Returns a list iterator over the elements in this list (in proper
684 * sequence), starting at the specified position in the list.
685 * The specified index indicates the first element that would be
686 * returned by an initial call to {@link ListIterator#next next}.
687 * An initial call to {@link ListIterator#previous previous} would
688 * return the element with the specified index minus one.
689 *
690 * @param index index of the first element to be returned from the
691 * list iterator (by a call to {@link ListIterator#next next})
692 * @return a list iterator over the elements in this list (in proper
693 * sequence), starting at the specified position in the list
694 * @throws IndexOutOfBoundsException if the index is out of range
695 * ({@code index < 0 || index > size()})
696 */
697 ListIterator<E> listIterator(int index);
698
699 // View
700
701 /**
702 * Returns a view of the portion of this list between the specified
703 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
704 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
705 * empty.) The returned list is backed by this list, so non-structural
706 * changes in the returned list are reflected in this list, and vice-versa.
707 * The returned list supports all of the optional list operations supported
708 * by this list.<p>
709 *
710 * This method eliminates the need for explicit range operations (of
711 * the sort that commonly exist for arrays). Any operation that expects
712 * a list can be used as a range operation by passing a subList view
713 * instead of a whole list. For example, the following idiom
714 * removes a range of elements from a list:
715 * <pre>{@code
716 * list.subList(from, to).clear();
717 * }</pre>
718 * Similar idioms may be constructed for {@code indexOf} and
719 * {@code lastIndexOf}, and all of the algorithms in the
720 * {@code Collections} class can be applied to a subList.<p>
721 *
722 * The semantics of the list returned by this method become undefined if
723 * the backing list (i.e., this list) is <i>structurally modified</i> in
724 * any way other than via the returned list. (Structural modifications are
725 * those that change the size of this list, or otherwise perturb it in such
726 * a fashion that iterations in progress may yield incorrect results.)
727 *
728 * @param fromIndex low endpoint (inclusive) of the subList
729 * @param toIndex high endpoint (exclusive) of the subList
730 * @return a view of the specified range within this list
731 * @throws IndexOutOfBoundsException for an illegal endpoint index value
732 * ({@code fromIndex < 0 || toIndex > size ||
733 * fromIndex > toIndex})
734 */
735 List<E> subList(int fromIndex, int toIndex);
736
737 /**
738 * Creates a {@link Spliterator} over the elements in this list.
739 *
740 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
741 * {@link Spliterator#ORDERED}. Implementations should document the
742 * reporting of additional characteristic values.
743 *
744 * @implSpec
745 * The default implementation creates a
746 * <em><a href="Spliterator.html#binding">late-binding</a></em>
747 * spliterator as follows:
748 * <ul>
749 * <li>If the list is an instance of {@link RandomAccess} then the default
750 * implementation creates a spliterator that traverses elements by
751 * invoking the method {@link List#get}. If such invocation results or
752 * would result in an {@code IndexOutOfBoundsException} then the
753 * spliterator will <em>fail-fast</em> and throw a
754 * {@code ConcurrentModificationException}.
755 * If the list is also an instance of {@link AbstractList} then the
756 * spliterator will use the list's {@link AbstractList#modCount modCount}
757 * field to provide additional <em>fail-fast</em> behavior.
758 * <li>Otherwise, the default implementation creates a spliterator from the
759 * list's {@code Iterator}. The spliterator inherits the
760 * <em>fail-fast</em> of the list's iterator.
761 * </ul>
762 *
763 * @implNote
764 * The created {@code Spliterator} additionally reports
765 * {@link Spliterator#SUBSIZED}.
766 *
767 * @return a {@code Spliterator} over the elements in this list
768 * @since 1.8
769 */
770 @Override
771 default Spliterator<E> spliterator() {
772 if (this instanceof RandomAccess) {
773 return new AbstractList.RandomAccessSpliterator<>(this);
774 } else {
775 return Spliterators.spliterator(this, Spliterator.ORDERED);
776 }
777 }
778
779 /**
780 * Returns an unmodifiable list containing zero elements.
781 *
782 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
783 *
784 * @param <E> the {@code List}'s element type
785 * @return an empty {@code List}
786 *
787 * @since 9
788 */
789 static <E> List<E> of() {
790 return ImmutableCollections.List0.instance();
791 }
792
793 /**
794 * Returns an unmodifiable list containing one element.
795 *
796 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
797 *
798 * @param <E> the {@code List}'s element type
799 * @param e1 the single element
800 * @return a {@code List} containing the specified element
801 * @throws NullPointerException if the element is {@code null}
802 *
803 * @since 9
804 */
805 static <E> List<E> of(E e1) {
806 return new ImmutableCollections.List1<>(e1);
807 }
808
809 /**
810 * Returns an unmodifiable list containing two elements.
811 *
812 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
813 *
814 * @param <E> the {@code List}'s element type
815 * @param e1 the first element
816 * @param e2 the second element
817 * @return a {@code List} containing the specified elements
818 * @throws NullPointerException if an element is {@code null}
819 *
820 * @since 9
821 */
822 static <E> List<E> of(E e1, E e2) {
823 return new ImmutableCollections.List2<>(e1, e2);
824 }
825
826 /**
827 * Returns an unmodifiable list containing three elements.
828 *
829 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
830 *
831 * @param <E> the {@code List}'s element type
832 * @param e1 the first element
833 * @param e2 the second element
834 * @param e3 the third element
835 * @return a {@code List} containing the specified elements
836 * @throws NullPointerException if an element is {@code null}
837 *
838 * @since 9
839 */
840 static <E> List<E> of(E e1, E e2, E e3) {
841 return new ImmutableCollections.ListN<>(e1, e2, e3);
842 }
843
844 /**
845 * Returns an unmodifiable list containing four elements.
846 *
847 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
848 *
849 * @param <E> the {@code List}'s element type
850 * @param e1 the first element
851 * @param e2 the second element
852 * @param e3 the third element
853 * @param e4 the fourth element
854 * @return a {@code List} containing the specified elements
855 * @throws NullPointerException if an element is {@code null}
856 *
857 * @since 9
858 */
859 static <E> List<E> of(E e1, E e2, E e3, E e4) {
860 return new ImmutableCollections.ListN<>(e1, e2, e3, e4);
861 }
862
863 /**
864 * Returns an unmodifiable list containing five elements.
865 *
866 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
867 *
868 * @param <E> the {@code List}'s element type
869 * @param e1 the first element
870 * @param e2 the second element
871 * @param e3 the third element
872 * @param e4 the fourth element
873 * @param e5 the fifth element
874 * @return a {@code List} containing the specified elements
875 * @throws NullPointerException if an element is {@code null}
876 *
877 * @since 9
878 */
879 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5) {
880 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5);
881 }
882
883 /**
884 * Returns an unmodifiable list containing six elements.
885 *
886 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
887 *
888 * @param <E> the {@code List}'s element type
889 * @param e1 the first element
890 * @param e2 the second element
891 * @param e3 the third element
892 * @param e4 the fourth element
893 * @param e5 the fifth element
894 * @param e6 the sixth element
895 * @return a {@code List} containing the specified elements
896 * @throws NullPointerException if an element is {@code null}
897 *
898 * @since 9
899 */
900 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
901 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
902 e6);
903 }
904
905 /**
906 * Returns an unmodifiable list containing seven elements.
907 *
908 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
909 *
910 * @param <E> the {@code List}'s element type
911 * @param e1 the first element
912 * @param e2 the second element
913 * @param e3 the third element
914 * @param e4 the fourth element
915 * @param e5 the fifth element
916 * @param e6 the sixth element
917 * @param e7 the seventh element
918 * @return a {@code List} containing the specified elements
919 * @throws NullPointerException if an element is {@code null}
920 *
921 * @since 9
922 */
923 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
924 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
925 e6, e7);
926 }
927
928 /**
929 * Returns an unmodifiable list containing eight elements.
930 *
931 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
932 *
933 * @param <E> the {@code List}'s element type
934 * @param e1 the first element
935 * @param e2 the second element
936 * @param e3 the third element
937 * @param e4 the fourth element
938 * @param e5 the fifth element
939 * @param e6 the sixth element
940 * @param e7 the seventh element
941 * @param e8 the eighth element
942 * @return a {@code List} containing the specified elements
943 * @throws NullPointerException if an element is {@code null}
944 *
945 * @since 9
946 */
947 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
948 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
949 e6, e7, e8);
950 }
951
952 /**
953 * Returns an unmodifiable list containing nine elements.
954 *
955 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
956 *
957 * @param <E> the {@code List}'s element type
958 * @param e1 the first element
959 * @param e2 the second element
960 * @param e3 the third element
961 * @param e4 the fourth element
962 * @param e5 the fifth element
963 * @param e6 the sixth element
964 * @param e7 the seventh element
965 * @param e8 the eighth element
966 * @param e9 the ninth element
967 * @return a {@code List} containing the specified elements
968 * @throws NullPointerException if an element is {@code null}
969 *
970 * @since 9
971 */
972 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
973 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
974 e6, e7, e8, e9);
975 }
976
977 /**
978 * Returns an unmodifiable list containing ten elements.
979 *
980 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
981 *
982 * @param <E> the {@code List}'s element type
983 * @param e1 the first element
984 * @param e2 the second element
985 * @param e3 the third element
986 * @param e4 the fourth element
987 * @param e5 the fifth element
988 * @param e6 the sixth element
989 * @param e7 the seventh element
990 * @param e8 the eighth element
991 * @param e9 the ninth element
992 * @param e10 the tenth element
993 * @return a {@code List} containing the specified elements
994 * @throws NullPointerException if an element is {@code null}
995 *
996 * @since 9
997 */
998 static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
999 return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
1000 e6, e7, e8, e9, e10);
1001 }
1002
1003 /**
1004 * Returns an unmodifiable list containing an arbitrary number of elements.
1005 * See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
1006 *
1007 * @apiNote
1008 * This method also accepts a single array as an argument. The element type of
1009 * the resulting list will be the component type of the array, and the size of
1010 * the list will be equal to the length of the array. To create a list with
1011 * a single element that is an array, do the following:
1012 *
1013 * <pre>{@code
1014 * String[] array = ... ;
1015 * List<String[]> list = List.<String[]>of(array);
1016 * }</pre>
1017 *
1018 * This will cause the {@link List#of(Object) List.of(E)} method
1019 * to be invoked instead.
1020 *
1021 * @param <E> the {@code List}'s element type
1022 * @param elements the elements to be contained in the list
1023 * @return a {@code List} containing the specified elements
1024 * @throws NullPointerException if an element is {@code null} or if the array is {@code null}
1025 *
1026 * @since 9
1027 */
1028 @SafeVarargs
1029 @SuppressWarnings("varargs")
1030 static <E> List<E> of(E... elements) {
1031 switch (elements.length) { // implicit null check of elements
1032 case 0:
1033 return ImmutableCollections.List0.instance();
1034 case 1:
1035 return new ImmutableCollections.List1<>(elements[0]);
1036 case 2:
1037 return new ImmutableCollections.List2<>(elements[0], elements[1]);
1038 default:
1039 return new ImmutableCollections.ListN<>(elements);
1040 }
1041 }
1042
1043 /**
1044 * Returns an <a href="#unmodifiable">unmodifiable List</a> containing the elements of
1045 * the given Collection, in its iteration order. The given Collection must not be null,
1046 * and it must not contain any null elements. If the given Collection is subsequently
1047 * modified, the returned List will not reflect such modifications.
1048 *
1049 * @param <E> the {@code List}'s element type
1050 * @param coll the collection from which elements are drawn, must be non-null
1051 * @return the new {@code List}
1052 * @throws NullPointerException if coll is null, or if it contains any nulls
1053 * @since 10
1054 */
1055 @SuppressWarnings("unchecked")
1056 static <E> List<E> copyOf(Collection<? extends E> coll) {
1057 if (coll instanceof ImmutableCollections.AbstractImmutableList) {
1058 return (List<E>)coll;
1059 } else {
1060 return (List<E>)List.of(coll.toArray());
1061 }
1062 }
1063 }