1 /*
2 * Copyright (c) 1997, 2013, 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
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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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24 */
25
26 package java.util;
27
28 /**
29 * A collection that contains no duplicate elements. More formally, sets
30 * contain no pair of elements {@code e1} and {@code e2} such that
31 * {@code e1.equals(e2)}, and at most one null element. As implied by
32 * its name, this interface models the mathematical <i>set</i> abstraction.
33 *
34 * <p>The {@code Set} interface places additional stipulations, beyond those
35 * inherited from the {@code Collection} interface, on the contracts of all
36 * constructors and on the contracts of the {@code add}, {@code equals} and
37 * {@code hashCode} methods. Declarations for other inherited methods are
38 * also included here for convenience. (The specifications accompanying these
39 * declarations have been tailored to the {@code Set} interface, but they do
40 * not contain any additional stipulations.)
41 *
42 * <p>The additional stipulation on constructors is, not surprisingly,
43 * that all constructors must create a set that contains no duplicate elements
44 * (as defined above).
45 *
46 * <p>Note: Great care must be exercised if mutable objects are used as set
47 * elements. The behavior of a set is not specified if the value of an object
48 * is changed in a manner that affects {@code equals} comparisons while the
49 * object is an element in the set. A special case of this prohibition is
50 * that it is not permissible for a set to contain itself as an element.
51 *
52 * <p>Some set implementations have restrictions on the elements that
53 * they may contain. For example, some implementations prohibit null elements,
54 * and some have restrictions on the types of their elements. Attempting to
55 * add an ineligible element throws an unchecked exception, typically
56 * {@code NullPointerException} or {@code ClassCastException}. Attempting
57 * to query the presence of an ineligible element may throw an exception,
58 * or it may simply return false; some implementations will exhibit the former
59 * behavior and some will exhibit the latter. More generally, attempting an
60 * operation on an ineligible element whose completion would not result in
61 * the insertion of an ineligible element into the set may throw an
62 * exception or it may succeed, at the option of the implementation.
63 * Such exceptions are marked as "optional" in the specification for this
64 * interface.
65 *
66 * <h2><a name="immutable">Immutable Set Factory Methods</a></h2>
67 * <p>The {@link Set#of(Object...) Set.of()} factory methods
68 * provide a convenient way to create immutable sets. The {@code Set}
69 * instances created by these methods have the following characteristics:
70 *
71 * <ul>
72 * <li>They cannot be modified. Attempts to modify them result in
73 * an {@code UnsupportedOperationException}.
74 * <li>They disallow null elements. Attempts to create them with
75 * null elements result in {@code NullPointerException}.
76 * <li>They are serializable if all elements are serializable.
77 * <li>They reject duplicate elements at creation time. Duplicate elements
78 * passed to a factory method result in {@code IllegalArgumentException}.
79 * </ul>
80 *
81 * <p>This interface is a member of the
82 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
83 * Java Collections Framework</a>.
84 *
85 * @param <E> the type of elements maintained by this set
86 *
87 * @author Josh Bloch
88 * @author Neal Gafter
89 * @see Collection
90 * @see List
91 * @see SortedSet
92 * @see HashSet
93 * @see TreeSet
94 * @see AbstractSet
95 * @see Collections#singleton(java.lang.Object)
96 * @see Collections#EMPTY_SET
97 * @since 1.2
98 */
99
100 public interface Set<E> extends Collection<E> {
101 // Query Operations
102
103 /**
104 * Returns the number of elements in this set (its cardinality). If this
105 * set contains more than {@code Integer.MAX_VALUE} elements, returns
106 * {@code Integer.MAX_VALUE}.
107 *
108 * @return the number of elements in this set (its cardinality)
109 */
110 int size();
111
112 /**
113 * Returns {@code true} if this set contains no elements.
114 *
115 * @return {@code true} if this set contains no elements
116 */
117 boolean isEmpty();
118
119 /**
120 * Returns {@code true} if this set contains the specified element.
121 * More formally, returns {@code true} if and only if this set
122 * contains an element {@code e} such that
123 * {@code Objects.equals(o, e)}.
124 *
125 * @param o element whose presence in this set is to be tested
126 * @return {@code true} if this set contains the specified element
127 * @throws ClassCastException if the type of the specified element
128 * is incompatible with this set
129 * (<a href="Collection.html#optional-restrictions">optional</a>)
130 * @throws NullPointerException if the specified element is null and this
131 * set does not permit null elements
132 * (<a href="Collection.html#optional-restrictions">optional</a>)
133 */
134 boolean contains(Object o);
135
136 /**
137 * Returns an iterator over the elements in this set. The elements are
138 * returned in no particular order (unless this set is an instance of some
139 * class that provides a guarantee).
140 *
141 * @return an iterator over the elements in this set
142 */
143 Iterator<E> iterator();
144
145 /**
146 * Returns an array containing all of the elements in this set.
147 * If this set makes any guarantees as to what order its elements
148 * are returned by its iterator, this method must return the
149 * elements in the same order.
150 *
151 * <p>The returned array will be "safe" in that no references to it
152 * are maintained by this set. (In other words, this method must
153 * allocate a new array even if this set is backed by an array).
154 * The caller is thus free to modify the returned array.
155 *
156 * <p>This method acts as bridge between array-based and collection-based
157 * APIs.
158 *
159 * @return an array containing all the elements in this set
160 */
161 Object[] toArray();
162
163 /**
164 * Returns an array containing all of the elements in this set; the
165 * runtime type of the returned array is that of the specified array.
166 * If the set fits in the specified array, it is returned therein.
167 * Otherwise, a new array is allocated with the runtime type of the
168 * specified array and the size of this set.
169 *
170 * <p>If this set fits in the specified array with room to spare
171 * (i.e., the array has more elements than this set), the element in
172 * the array immediately following the end of the set is set to
173 * {@code null}. (This is useful in determining the length of this
174 * set <i>only</i> if the caller knows that this set does not contain
175 * any null elements.)
176 *
177 * <p>If this set makes any guarantees as to what order its elements
178 * are returned by its iterator, this method must return the elements
179 * in the same order.
180 *
181 * <p>Like the {@link #toArray()} method, this method acts as bridge between
182 * array-based and collection-based APIs. Further, this method allows
183 * precise control over the runtime type of the output array, and may,
184 * under certain circumstances, be used to save allocation costs.
185 *
186 * <p>Suppose {@code x} is a set known to contain only strings.
187 * The following code can be used to dump the set into a newly allocated
188 * array of {@code String}:
189 *
190 * <pre>
191 * String[] y = x.toArray(new String[0]);</pre>
192 *
193 * Note that {@code toArray(new Object[0])} is identical in function to
194 * {@code toArray()}.
195 *
196 * @param a the array into which the elements of this set are to be
197 * stored, if it is big enough; otherwise, a new array of the same
198 * runtime type is allocated for this purpose.
199 * @return an array containing all the elements in this set
200 * @throws ArrayStoreException if the runtime type of the specified array
201 * is not a supertype of the runtime type of every element in this
202 * set
203 * @throws NullPointerException if the specified array is null
204 */
205 <T> T[] toArray(T[] a);
206
207
208 // Modification Operations
209
210 /**
211 * Adds the specified element to this set if it is not already present
212 * (optional operation). More formally, adds the specified element
213 * {@code e} to this set if the set contains no element {@code e2}
214 * such that
215 * {@code Objects.equals(e, e2)}.
216 * If this set already contains the element, the call leaves the set
217 * unchanged and returns {@code false}. In combination with the
218 * restriction on constructors, this ensures that sets never contain
219 * duplicate elements.
220 *
221 * <p>The stipulation above does not imply that sets must accept all
222 * elements; sets may refuse to add any particular element, including
223 * {@code null}, and throw an exception, as described in the
224 * specification for {@link Collection#add Collection.add}.
225 * Individual set implementations should clearly document any
226 * restrictions on the elements that they may contain.
227 *
228 * @param e element to be added to this set
229 * @return {@code true} if this set did not already contain the specified
230 * element
231 * @throws UnsupportedOperationException if the {@code add} operation
232 * is not supported by this set
233 * @throws ClassCastException if the class of the specified element
234 * prevents it from being added to this set
235 * @throws NullPointerException if the specified element is null and this
236 * set does not permit null elements
237 * @throws IllegalArgumentException if some property of the specified element
238 * prevents it from being added to this set
239 */
240 boolean add(E e);
241
242
243 /**
244 * Removes the specified element from this set if it is present
245 * (optional operation). More formally, removes an element {@code e}
246 * such that
247 * {@code Objects.equals(o, e)}, if
248 * this set contains such an element. Returns {@code true} if this set
249 * contained the element (or equivalently, if this set changed as a
250 * result of the call). (This set will not contain the element once the
251 * call returns.)
252 *
253 * @param o object to be removed from this set, if present
254 * @return {@code true} if this set contained the specified element
255 * @throws ClassCastException if the type of the specified element
256 * is incompatible with this set
257 * (<a href="Collection.html#optional-restrictions">optional</a>)
258 * @throws NullPointerException if the specified element is null and this
259 * set does not permit null elements
260 * (<a href="Collection.html#optional-restrictions">optional</a>)
261 * @throws UnsupportedOperationException if the {@code remove} operation
262 * is not supported by this set
263 */
264 boolean remove(Object o);
265
266
267 // Bulk Operations
268
269 /**
270 * Returns {@code true} if this set contains all of the elements of the
271 * specified collection. If the specified collection is also a set, this
272 * method returns {@code true} if it is a <i>subset</i> of this set.
273 *
274 * @param c collection to be checked for containment in this set
275 * @return {@code true} if this set contains all of the elements of the
276 * specified collection
277 * @throws ClassCastException if the types of one or more elements
278 * in the specified collection are incompatible with this
279 * set
280 * (<a href="Collection.html#optional-restrictions">optional</a>)
281 * @throws NullPointerException if the specified collection contains one
282 * or more null elements and this set does not permit null
283 * elements
284 * (<a href="Collection.html#optional-restrictions">optional</a>),
285 * or if the specified collection is null
286 * @see #contains(Object)
287 */
288 boolean containsAll(Collection<?> c);
289
290 /**
291 * Adds all of the elements in the specified collection to this set if
292 * they're not already present (optional operation). If the specified
293 * collection is also a set, the {@code addAll} operation effectively
294 * modifies this set so that its value is the <i>union</i> of the two
295 * sets. The behavior of this operation is undefined if the specified
296 * collection is modified while the operation is in progress.
297 *
298 * @param c collection containing elements to be added to this set
299 * @return {@code true} if this set changed as a result of the call
300 *
301 * @throws UnsupportedOperationException if the {@code addAll} operation
302 * is not supported by this set
303 * @throws ClassCastException if the class of an element of the
304 * specified collection prevents it from being added to this set
305 * @throws NullPointerException if the specified collection contains one
306 * or more null elements and this set does not permit null
307 * elements, or if the specified collection is null
308 * @throws IllegalArgumentException if some property of an element of the
309 * specified collection prevents it from being added to this set
310 * @see #add(Object)
311 */
312 boolean addAll(Collection<? extends E> c);
313
314 /**
315 * Retains only the elements in this set that are contained in the
316 * specified collection (optional operation). In other words, removes
317 * from this set all of its elements that are not contained in the
318 * specified collection. If the specified collection is also a set, this
319 * operation effectively modifies this set so that its value is the
320 * <i>intersection</i> of the two sets.
321 *
322 * @param c collection containing elements to be retained in this set
323 * @return {@code true} if this set changed as a result of the call
324 * @throws UnsupportedOperationException if the {@code retainAll} operation
325 * is not supported by this set
326 * @throws ClassCastException if the class of an element of this set
327 * is incompatible with the specified collection
328 * (<a href="Collection.html#optional-restrictions">optional</a>)
329 * @throws NullPointerException if this set contains a null element and the
330 * specified collection does not permit null elements
331 * (<a href="Collection.html#optional-restrictions">optional</a>),
332 * or if the specified collection is null
333 * @see #remove(Object)
334 */
335 boolean retainAll(Collection<?> c);
336
337 /**
338 * Removes from this set all of its elements that are contained in the
339 * specified collection (optional operation). If the specified
340 * collection is also a set, this operation effectively modifies this
341 * set so that its value is the <i>asymmetric set difference</i> of
342 * the two sets.
343 *
344 * @param c collection containing elements to be removed from this set
345 * @return {@code true} if this set changed as a result of the call
346 * @throws UnsupportedOperationException if the {@code removeAll} operation
347 * is not supported by this set
348 * @throws ClassCastException if the class of an element of this set
349 * is incompatible with the specified collection
350 * (<a href="Collection.html#optional-restrictions">optional</a>)
351 * @throws NullPointerException if this set contains a null element and the
352 * specified collection does not permit null elements
353 * (<a href="Collection.html#optional-restrictions">optional</a>),
354 * or if the specified collection is null
355 * @see #remove(Object)
356 * @see #contains(Object)
357 */
358 boolean removeAll(Collection<?> c);
359
360 /**
361 * Removes all of the elements from this set (optional operation).
362 * The set will be empty after this call returns.
363 *
364 * @throws UnsupportedOperationException if the {@code clear} method
365 * is not supported by this set
366 */
367 void clear();
368
369
370 // Comparison and hashing
371
372 /**
373 * Compares the specified object with this set for equality. Returns
374 * {@code true} if the specified object is also a set, the two sets
375 * have the same size, and every member of the specified set is
376 * contained in this set (or equivalently, every member of this set is
377 * contained in the specified set). This definition ensures that the
378 * equals method works properly across different implementations of the
379 * set interface.
380 *
381 * @param o object to be compared for equality with this set
382 * @return {@code true} if the specified object is equal to this set
383 */
384 boolean equals(Object o);
385
386 /**
387 * Returns the hash code value for this set. The hash code of a set is
388 * defined to be the sum of the hash codes of the elements in the set,
389 * where the hash code of a {@code null} element is defined to be zero.
390 * This ensures that {@code s1.equals(s2)} implies that
391 * {@code s1.hashCode()==s2.hashCode()} for any two sets {@code s1}
392 * and {@code s2}, as required by the general contract of
393 * {@link Object#hashCode}.
394 *
395 * @return the hash code value for this set
396 * @see Object#equals(Object)
397 * @see Set#equals(Object)
398 */
399 int hashCode();
400
401 /**
402 * Creates a {@code Spliterator} over the elements in this set.
403 *
404 * <p>The {@code Spliterator} reports {@link Spliterator#DISTINCT}.
405 * Implementations should document the reporting of additional
406 * characteristic values.
407 *
408 * @implSpec
409 * The default implementation creates a
410 * <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
411 * from the set's {@code Iterator}. The spliterator inherits the
412 * <em>fail-fast</em> properties of the set's iterator.
413 * <p>
414 * The created {@code Spliterator} additionally reports
415 * {@link Spliterator#SIZED}.
416 *
417 * @implNote
418 * The created {@code Spliterator} additionally reports
419 * {@link Spliterator#SUBSIZED}.
420 *
421 * @return a {@code Spliterator} over the elements in this set
422 * @since 1.8
423 */
424 @Override
425 default Spliterator<E> spliterator() {
426 return Spliterators.spliterator(this, Spliterator.DISTINCT);
427 }
428
429 /**
430 * Creates an immutable set containing zero elements.
431 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
432 *
433 * @param <E> the set's element type
434 * @return the newly created set
435 *
436 * @since 1.9
437 */
438 static <E> Set<E> of() {
439 return Collections.emptySet();
440 }
441
442 /**
443 * Creates an immutable set containing one element.
444 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
445 *
446 * @param <E> the set's element type
447 * @param e1 the single set element
448 * @return the newly created set
449 * @throws NullPointerException if the element is null
450 *
451 * @since 1.9
452 */
453 static <E> Set<E> of(E e1) {
454 return Collections.singleton(Objects.requireNonNull(e1));
455 }
456
457 /**
458 * Creates an immutable set containing two elements.
459 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
460 *
461 * @param <E> the set's element type
462 * @param e1 the first set element
463 * @param e2 the second set element
464 * @return the newly created set
465 * @throws IllegalArgumentException if the elements are duplicates
466 * @throws NullPointerException if an element is null
467 *
468 * @since 1.9
469 */
470 static <E> Set<E> of(E e1, E e2) {
471 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
472 Objects.requireNonNull(e2)));
473 if (set.size() != 2) {
474 throw new IllegalArgumentException("duplicate elements");
475 }
476 return Collections.unmodifiableSet(set);
477 }
478
479 /**
480 * Creates an immutable set containing three elements.
481 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
482 *
483 * @param <E> the set's element type
484 * @param e1 the first set element
485 * @param e2 the second set element
486 * @param e3 the third set element
487 * @return the newly created set
488 * @throws IllegalArgumentException if there are any duplicate elements
489 * @throws NullPointerException if an element is null
490 *
491 * @since 1.9
492 */
493 static <E> Set<E> of(E e1, E e2, E e3) {
494 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
495 Objects.requireNonNull(e2),
496 Objects.requireNonNull(e3)));
497 if (set.size() != 3) {
498 throw new IllegalArgumentException("duplicate elements");
499 }
500 return Collections.unmodifiableSet(set);
501 }
502
503 /**
504 * Creates an immutable set containing four elements.
505 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
506 *
507 * @param <E> the set's element type
508 * @param e1 the first set element
509 * @param e2 the second set element
510 * @param e3 the third set element
511 * @param e4 the fourth set element
512 * @return the newly created set
513 * @throws IllegalArgumentException if there are any duplicate elements
514 * @throws NullPointerException if an element is null
515 *
516 * @since 1.9
517 */
518 static <E> Set<E> of(E e1, E e2, E e3, E e4) {
519 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
520 Objects.requireNonNull(e2),
521 Objects.requireNonNull(e3),
522 Objects.requireNonNull(e4)));
523 if (set.size() != 4) {
524 throw new IllegalArgumentException("duplicate elements");
525 }
526 return Collections.unmodifiableSet(set);
527 }
528
529 /**
530 * Creates an immutable set containing five elements.
531 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
532 *
533 * @param <E> the set's element type
534 * @param e1 the first set element
535 * @param e2 the second set element
536 * @param e3 the third set element
537 * @param e4 the fourth set element
538 * @param e5 the fifth set element
539 * @return the newly created set
540 * @throws IllegalArgumentException if there are any duplicate elements
541 * @throws NullPointerException if an element is null
542 *
543 * @since 1.9
544 */
545 static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5) {
546 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
547 Objects.requireNonNull(e2),
548 Objects.requireNonNull(e3),
549 Objects.requireNonNull(e4),
550 Objects.requireNonNull(e5)));
551 if (set.size() != 5) {
552 throw new IllegalArgumentException("duplicate elements");
553 }
554 return Collections.unmodifiableSet(set);
555 }
556
557 /**
558 * Creates an immutable set containing six elements.
559 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
560 *
561 * @param <E> the set's element type
562 * @param e1 the first set element
563 * @param e2 the second set element
564 * @param e3 the third set element
565 * @param e4 the fourth set element
566 * @param e5 the fifth set element
567 * @param e6 the sixth set element
568 * @return the newly created set
569 * @throws IllegalArgumentException if there are any duplicate elements
570 * @throws NullPointerException if an element is null
571 *
572 * @since 1.9
573 */
574 static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
575 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
576 Objects.requireNonNull(e2),
577 Objects.requireNonNull(e3),
578 Objects.requireNonNull(e4),
579 Objects.requireNonNull(e5),
580 Objects.requireNonNull(e6)));
581 if (set.size() != 6) {
582 throw new IllegalArgumentException("duplicate elements");
583 }
584 return Collections.unmodifiableSet(set);
585 }
586
587 /**
588 * Creates an immutable set containing seven elements.
589 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
590 *
591 * @param <E> the set's element type
592 * @param e1 the first set element
593 * @param e2 the second set element
594 * @param e3 the third set element
595 * @param e4 the fourth set element
596 * @param e5 the fifth set element
597 * @param e6 the sixth set element
598 * @param e7 the seventh set element
599 * @return the newly created set
600 * @throws IllegalArgumentException if there are any duplicate elements
601 * @throws NullPointerException if an element is null
602 *
603 * @since 1.9
604 */
605 static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
606 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
607 Objects.requireNonNull(e2),
608 Objects.requireNonNull(e3),
609 Objects.requireNonNull(e4),
610 Objects.requireNonNull(e5),
611 Objects.requireNonNull(e6),
612 Objects.requireNonNull(e7)));
613 if (set.size() != 7) {
614 throw new IllegalArgumentException("duplicate elements");
615 }
616 return Collections.unmodifiableSet(set);
617 }
618
619 /**
620 * Creates an immutable set containing eight elements.
621 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
622 *
623 * @param <E> the set's element type
624 * @param e1 the first set element
625 * @param e2 the second set element
626 * @param e3 the third set element
627 * @param e4 the fourth set element
628 * @param e5 the fifth set element
629 * @param e6 the sixth set element
630 * @param e7 the seventh set element
631 * @param e8 the eighth set element
632 * @return the newly created set
633 * @throws IllegalArgumentException if there are any duplicate elements
634 * @throws NullPointerException if an element is null
635 *
636 * @since 1.9
637 */
638 static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
639 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
640 Objects.requireNonNull(e2),
641 Objects.requireNonNull(e3),
642 Objects.requireNonNull(e4),
643 Objects.requireNonNull(e5),
644 Objects.requireNonNull(e6),
645 Objects.requireNonNull(e7),
646 Objects.requireNonNull(e8)));
647 if (set.size() != 8) {
648 throw new IllegalArgumentException("duplicate elements");
649 }
650 return Collections.unmodifiableSet(set);
651 }
652
653 /**
654 * Creates an immutable set containing nine elements.
655 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
656 *
657 * @param <E> the set's element type
658 * @param e1 the first set element
659 * @param e2 the second set element
660 * @param e3 the third set element
661 * @param e4 the fourth set element
662 * @param e5 the fifth set element
663 * @param e6 the sixth set element
664 * @param e7 the seventh set element
665 * @param e8 the eighth set element
666 * @param e9 the ninth set element
667 * @return the newly created set
668 * @throws IllegalArgumentException if there are any duplicate elements
669 * @throws NullPointerException if an element is null
670 *
671 * @since 1.9
672 */
673 static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
674 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
675 Objects.requireNonNull(e2),
676 Objects.requireNonNull(e3),
677 Objects.requireNonNull(e4),
678 Objects.requireNonNull(e5),
679 Objects.requireNonNull(e6),
680 Objects.requireNonNull(e7),
681 Objects.requireNonNull(e8),
682 Objects.requireNonNull(e9)));
683 if (set.size() != 9) {
684 throw new IllegalArgumentException("duplicate elements");
685 }
686 return Collections.unmodifiableSet(set);
687 }
688
689 /**
690 * Creates an immutable set containing ten elements.
691 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
692 *
693 * @param <E> the set's element type
694 * @param e1 the first set element
695 * @param e2 the second set element
696 * @param e3 the third set element
697 * @param e4 the fourth set element
698 * @param e5 the fifth set element
699 * @param e6 the sixth set element
700 * @param e7 the seventh set element
701 * @param e8 the eighth set element
702 * @param e9 the ninth set element
703 * @param e10 the tenth set element
704 * @return the newly created set
705 * @throws IllegalArgumentException if there are any duplicate elements
706 * @throws NullPointerException if an element is null
707 *
708 * @since 1.9
709 */
710 static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
711 Set<E> set = new HashSet<>(Arrays.asList(Objects.requireNonNull(e1),
712 Objects.requireNonNull(e2),
713 Objects.requireNonNull(e3),
714 Objects.requireNonNull(e4),
715 Objects.requireNonNull(e5),
716 Objects.requireNonNull(e6),
717 Objects.requireNonNull(e7),
718 Objects.requireNonNull(e8),
719 Objects.requireNonNull(e9),
720 Objects.requireNonNull(e10)));
721 if (set.size() != 10) {
722 throw new IllegalArgumentException("duplicate elements");
723 }
724 return Collections.unmodifiableSet(set);
725 }
726
727 /**
728 * Creates an immutable set containing an arbitrary number of elements.
729 * See <a href="#immutable">Immutable Set Factory Methods</a> for details.
730 *
731 * @apiNote
732 * This method also accepts a single array as an argument. The element type of
733 * the resulting set will be the component type of the array, and the size of
734 * the set will be equal to the length of the array. To create a set with
735 * a single element that is an array, do the following:
736 *
737 * <pre>{@code
738 * String[] array = ... ;
739 * Set<String[]> list = Set.<String[]>of(array);
740 * }</pre>
741 *
742 * This will cause the {@link Set#of(Object) Set.of(E)} method
743 * to be invoked instead.
744 *
745 * @param <E> the set's element type
746 * @param es the elements to be contained in the set
747 * @return the newly created set
748 * @throws IllegalArgumentException if there are any duplicate elements
749 * @throws NullPointerException if an element is null
750 *
751 * @since 1.9
752 */
753 @SafeVarargs
754 @SuppressWarnings("varargs")
755 static <E> Set<E> of(E... es) {
756 for (E e : es) {
757 Objects.requireNonNull(e);
758 }
759 // NOTE: this can allow a null element to slip through
760 Set<E> set = new HashSet<>(Arrays.asList(es));
761 if (set.size() != es.length) {
762 throw new IllegalArgumentException("duplicate elements");
763 }
764 return Collections.unmodifiableSet(set);
765 }
766 }