736 lines
31 KiB
Java
736 lines
31 KiB
Java
/*
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* Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util;
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/**
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* A collection that contains no duplicate elements. More formally, sets
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* contain no pair of elements {@code e1} and {@code e2} such that
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* {@code e1.equals(e2)}, and at most one null element. As implied by
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* its name, this interface models the mathematical <i>set</i> abstraction.
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*
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* <p>The {@code Set} interface places additional stipulations, beyond those
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* inherited from the {@code Collection} interface, on the contracts of all
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* constructors and on the contracts of the {@code add}, {@code equals} and
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* {@code hashCode} methods. Declarations for other inherited methods are
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* also included here for convenience. (The specifications accompanying these
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* declarations have been tailored to the {@code Set} interface, but they do
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* not contain any additional stipulations.)
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*
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* <p>The additional stipulation on constructors is, not surprisingly,
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* that all constructors must create a set that contains no duplicate elements
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* (as defined above).
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*
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* <p>Note: Great care must be exercised if mutable objects are used as set
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* elements. The behavior of a set is not specified if the value of an object
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* is changed in a manner that affects {@code equals} comparisons while the
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* object is an element in the set. A special case of this prohibition is
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* that it is not permissible for a set to contain itself as an element.
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*
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* <p>Some set implementations have restrictions on the elements that
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* they may contain. For example, some implementations prohibit null elements,
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* and some have restrictions on the types of their elements. Attempting to
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* add an ineligible element throws an unchecked exception, typically
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* {@code NullPointerException} or {@code ClassCastException}. Attempting
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* to query the presence of an ineligible element may throw an exception,
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* or it may simply return false; some implementations will exhibit the former
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* behavior and some will exhibit the latter. More generally, attempting an
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* operation on an ineligible element whose completion would not result in
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* the insertion of an ineligible element into the set may throw an
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* exception or it may succeed, at the option of the implementation.
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* Such exceptions are marked as "optional" in the specification for this
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* interface.
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*
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* <h2><a id="unmodifiable">Unmodifiable Sets</a></h2>
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* <p>The {@link Set#of(Object...) Set.of} and
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* {@link Set#copyOf Set.copyOf} static factory methods
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* provide a convenient way to create unmodifiable sets. The {@code Set}
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* instances created by these methods have the following characteristics:
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*
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* <ul>
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* <li>They are <a href="Collection.html#unmodifiable"><i>unmodifiable</i></a>. Elements cannot
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* be added or removed. Calling any mutator method on the Set
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* will always cause {@code UnsupportedOperationException} to be thrown.
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* However, if the contained elements are themselves mutable, this may cause the
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* Set to behave inconsistently or its contents to appear to change.
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* <li>They disallow {@code null} elements. Attempts to create them with
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* {@code null} elements result in {@code NullPointerException}.
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* <li>They are serializable if all elements are serializable.
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* <li>They reject duplicate elements at creation time. Duplicate elements
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* passed to a static factory method result in {@code IllegalArgumentException}.
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* <li>The iteration order of set elements is unspecified and is subject to change.
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* <li>They are <a href="../lang/doc-files/ValueBased.html">value-based</a>.
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* Programmers should treat instances that are {@linkplain #equals(Object) equal}
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* as interchangeable and should not use them for synchronization, or
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* unpredictable behavior may occur. For example, in a future release,
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* synchronization may fail. Callers should make no assumptions
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* about the identity of the returned instances. Factories are free to
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* create new instances or reuse existing ones.
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* <li>They are serialized as specified on the
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* <a href="{@docRoot}/serialized-form.html#java.util.CollSer">Serialized Form</a>
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* page.
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* </ul>
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*
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* <p>This interface is a member of the
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* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
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* Java Collections Framework</a>.
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*
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* @param <E> the type of elements maintained by this set
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*
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* @author Josh Bloch
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* @author Neal Gafter
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* @see Collection
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* @see List
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* @see SortedSet
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* @see HashSet
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* @see TreeSet
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* @see AbstractSet
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* @see Collections#singleton(java.lang.Object)
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* @see Collections#EMPTY_SET
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* @since 1.2
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*/
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public interface Set<E> extends Collection<E> {
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// Query Operations
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/**
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* Returns the number of elements in this set (its cardinality). If this
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* set contains more than {@code Integer.MAX_VALUE} elements, returns
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* {@code Integer.MAX_VALUE}.
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*
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* @return the number of elements in this set (its cardinality)
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*/
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int size();
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/**
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* Returns {@code true} if this set contains no elements.
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*
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* @return {@code true} if this set contains no elements
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*/
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boolean isEmpty();
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/**
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* Returns {@code true} if this set contains the specified element.
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* More formally, returns {@code true} if and only if this set
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* contains an element {@code e} such that
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* {@code Objects.equals(o, e)}.
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*
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* @param o element whose presence in this set is to be tested
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* @return {@code true} if this set contains the specified element
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* @throws ClassCastException if the type of the specified element
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* is incompatible with this set
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* (<a href="Collection.html#optional-restrictions">optional</a>)
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* @throws NullPointerException if the specified element is null and this
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* set does not permit null elements
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* (<a href="Collection.html#optional-restrictions">optional</a>)
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*/
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boolean contains(Object o);
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/**
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* Returns an iterator over the elements in this set. The elements are
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* returned in no particular order (unless this set is an instance of some
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* class that provides a guarantee).
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*
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* @return an iterator over the elements in this set
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*/
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Iterator<E> iterator();
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/**
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* Returns an array containing all of the elements in this set.
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* If this set makes any guarantees as to what order its elements
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* are returned by its iterator, this method must return the
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* elements in the same order.
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*
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* <p>The returned array will be "safe" in that no references to it
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* are maintained by this set. (In other words, this method must
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* allocate a new array even if this set is backed by an array).
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* The caller is thus free to modify the returned array.
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*
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* <p>This method acts as bridge between array-based and collection-based
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* APIs.
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*
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* @return an array containing all the elements in this set
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*/
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Object[] toArray();
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/**
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* Returns an array containing all of the elements in this set; the
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* runtime type of the returned array is that of the specified array.
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* If the set fits in the specified array, it is returned therein.
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* Otherwise, a new array is allocated with the runtime type of the
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* specified array and the size of this set.
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*
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* <p>If this set fits in the specified array with room to spare
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* (i.e., the array has more elements than this set), the element in
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* the array immediately following the end of the set is set to
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* {@code null}. (This is useful in determining the length of this
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* set <i>only</i> if the caller knows that this set does not contain
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* any null elements.)
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*
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* <p>If this set makes any guarantees as to what order its elements
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* are returned by its iterator, this method must return the elements
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* in the same order.
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*
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* <p>Like the {@link #toArray()} method, this method acts as bridge between
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* array-based and collection-based APIs. Further, this method allows
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* precise control over the runtime type of the output array, and may,
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* under certain circumstances, be used to save allocation costs.
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*
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* <p>Suppose {@code x} is a set known to contain only strings.
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* The following code can be used to dump the set into a newly allocated
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* array of {@code String}:
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*
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* <pre>
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* String[] y = x.toArray(new String[0]);</pre>
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*
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* Note that {@code toArray(new Object[0])} is identical in function to
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* {@code toArray()}.
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*
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* @param a the array into which the elements of this set are to be
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* stored, if it is big enough; otherwise, a new array of the same
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* runtime type is allocated for this purpose.
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* @return an array containing all the elements in this set
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* @throws ArrayStoreException if the runtime type of the specified array
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* is not a supertype of the runtime type of every element in this
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* set
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* @throws NullPointerException if the specified array is null
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*/
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<T> T[] toArray(T[] a);
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// Modification Operations
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/**
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* Adds the specified element to this set if it is not already present
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* (optional operation). More formally, adds the specified element
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* {@code e} to this set if the set contains no element {@code e2}
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* such that
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* {@code Objects.equals(e, e2)}.
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* If this set already contains the element, the call leaves the set
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* unchanged and returns {@code false}. In combination with the
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* restriction on constructors, this ensures that sets never contain
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* duplicate elements.
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*
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* <p>The stipulation above does not imply that sets must accept all
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* elements; sets may refuse to add any particular element, including
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* {@code null}, and throw an exception, as described in the
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* specification for {@link Collection#add Collection.add}.
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* Individual set implementations should clearly document any
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* restrictions on the elements that they may contain.
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*
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* @param e element to be added to this set
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* @return {@code true} if this set did not already contain the specified
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* element
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* @throws UnsupportedOperationException if the {@code add} operation
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* is not supported by this set
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this set
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* @throws NullPointerException if the specified element is null and this
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* set does not permit null elements
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* @throws IllegalArgumentException if some property of the specified element
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* prevents it from being added to this set
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*/
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boolean add(E e);
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/**
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* Removes the specified element from this set if it is present
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* (optional operation). More formally, removes an element {@code e}
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* such that
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* {@code Objects.equals(o, e)}, if
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* this set contains such an element. Returns {@code true} if this set
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* contained the element (or equivalently, if this set changed as a
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* result of the call). (This set will not contain the element once the
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* call returns.)
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*
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* @param o object to be removed from this set, if present
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* @return {@code true} if this set contained the specified element
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* @throws ClassCastException if the type of the specified element
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* is incompatible with this set
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* (<a href="Collection.html#optional-restrictions">optional</a>)
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* @throws NullPointerException if the specified element is null and this
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* set does not permit null elements
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* (<a href="Collection.html#optional-restrictions">optional</a>)
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* @throws UnsupportedOperationException if the {@code remove} operation
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* is not supported by this set
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*/
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boolean remove(Object o);
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// Bulk Operations
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/**
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* Returns {@code true} if this set contains all of the elements of the
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* specified collection. If the specified collection is also a set, this
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* method returns {@code true} if it is a <i>subset</i> of this set.
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*
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* @param c collection to be checked for containment in this set
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* @return {@code true} if this set contains all of the elements of the
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* specified collection
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* @throws ClassCastException if the types of one or more elements
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* in the specified collection are incompatible with this
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* set
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* (<a href="Collection.html#optional-restrictions">optional</a>)
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* @throws NullPointerException if the specified collection contains one
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* or more null elements and this set does not permit null
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* elements
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* (<a href="Collection.html#optional-restrictions">optional</a>),
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* or if the specified collection is null
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* @see #contains(Object)
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*/
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boolean containsAll(Collection<?> c);
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/**
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* Adds all of the elements in the specified collection to this set if
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* they're not already present (optional operation). If the specified
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* collection is also a set, the {@code addAll} operation effectively
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* modifies this set so that its value is the <i>union</i> of the two
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* sets. The behavior of this operation is undefined if the specified
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* collection is modified while the operation is in progress.
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*
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* @param c collection containing elements to be added to this set
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* @return {@code true} if this set changed as a result of the call
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*
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* @throws UnsupportedOperationException if the {@code addAll} operation
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* is not supported by this set
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* @throws ClassCastException if the class of an element of the
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* specified collection prevents it from being added to this set
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* @throws NullPointerException if the specified collection contains one
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* or more null elements and this set does not permit null
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* elements, or if the specified collection is null
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* @throws IllegalArgumentException if some property of an element of the
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* specified collection prevents it from being added to this set
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* @see #add(Object)
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*/
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boolean addAll(Collection<? extends E> c);
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/**
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* Retains only the elements in this set that are contained in the
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* specified collection (optional operation). In other words, removes
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* from this set all of its elements that are not contained in the
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* specified collection. If the specified collection is also a set, this
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* operation effectively modifies this set so that its value is the
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* <i>intersection</i> of the two sets.
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*
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* @param c collection containing elements to be retained in this set
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* @return {@code true} if this set changed as a result of the call
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* @throws UnsupportedOperationException if the {@code retainAll} operation
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* is not supported by this set
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* @throws ClassCastException if the class of an element of this set
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* is incompatible with the specified collection
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* (<a href="Collection.html#optional-restrictions">optional</a>)
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* @throws NullPointerException if this set contains a null element and the
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* specified collection does not permit null elements
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* (<a href="Collection.html#optional-restrictions">optional</a>),
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* or if the specified collection is null
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* @see #remove(Object)
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*/
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boolean retainAll(Collection<?> c);
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/**
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* Removes from this set all of its elements that are contained in the
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* specified collection (optional operation). If the specified
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* collection is also a set, this operation effectively modifies this
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* set so that its value is the <i>asymmetric set difference</i> of
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* the two sets.
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*
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* @param c collection containing elements to be removed from this set
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* @return {@code true} if this set changed as a result of the call
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* @throws UnsupportedOperationException if the {@code removeAll} operation
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* is not supported by this set
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* @throws ClassCastException if the class of an element of this set
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* is incompatible with the specified collection
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* (<a href="Collection.html#optional-restrictions">optional</a>)
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* @throws NullPointerException if this set contains a null element and the
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* specified collection does not permit null elements
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* (<a href="Collection.html#optional-restrictions">optional</a>),
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* or if the specified collection is null
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* @see #remove(Object)
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* @see #contains(Object)
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*/
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boolean removeAll(Collection<?> c);
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/**
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* Removes all of the elements from this set (optional operation).
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* The set will be empty after this call returns.
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*
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* @throws UnsupportedOperationException if the {@code clear} method
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* is not supported by this set
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*/
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void clear();
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// Comparison and hashing
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/**
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* Compares the specified object with this set for equality. Returns
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* {@code true} if the specified object is also a set, the two sets
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* have the same size, and every member of the specified set is
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* contained in this set (or equivalently, every member of this set is
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* contained in the specified set). This definition ensures that the
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* equals method works properly across different implementations of the
|
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* set interface.
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*
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* @param o object to be compared for equality with this set
|
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* @return {@code true} if the specified object is equal to this set
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*/
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boolean equals(Object o);
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/**
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* Returns the hash code value for this set. The hash code of a set is
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* defined to be the sum of the hash codes of the elements in the set,
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* where the hash code of a {@code null} element is defined to be zero.
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* This ensures that {@code s1.equals(s2)} implies that
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* {@code s1.hashCode()==s2.hashCode()} for any two sets {@code s1}
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* and {@code s2}, as required by the general contract of
|
|
* {@link Object#hashCode}.
|
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*
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* @return the hash code value for this set
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|
* @see Object#equals(Object)
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* @see Set#equals(Object)
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*/
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int hashCode();
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|
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/**
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* Creates a {@code Spliterator} over the elements in this set.
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*
|
|
* <p>The {@code Spliterator} reports {@link Spliterator#DISTINCT}.
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* Implementations should document the reporting of additional
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* characteristic values.
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*
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* @implSpec
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* The default implementation creates a
|
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* <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
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* from the set's {@code Iterator}. The spliterator inherits the
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* <em>fail-fast</em> properties of the set's iterator.
|
|
* <p>
|
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* The created {@code Spliterator} additionally reports
|
|
* {@link Spliterator#SIZED}.
|
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*
|
|
* @implNote
|
|
* The created {@code Spliterator} additionally reports
|
|
* {@link Spliterator#SUBSIZED}.
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|
*
|
|
* @return a {@code Spliterator} over the elements in this set
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* @since 1.8
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*/
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@Override
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default Spliterator<E> spliterator() {
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return Spliterators.spliterator(this, Spliterator.DISTINCT);
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}
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|
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/**
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* Returns an unmodifiable set containing zero elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @return an empty {@code Set}
|
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*
|
|
* @since 9
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*/
|
|
@SuppressWarnings("unchecked")
|
|
static <E> Set<E> of() {
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return (Set<E>) ImmutableCollections.EMPTY_SET;
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}
|
|
|
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/**
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|
* Returns an unmodifiable set containing one element.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the single element
|
|
* @return a {@code Set} containing the specified element
|
|
* @throws NullPointerException if the element is {@code null}
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|
*
|
|
* @since 9
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|
*/
|
|
static <E> Set<E> of(E e1) {
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return new ImmutableCollections.Set12<>(e1);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing two elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if the elements are duplicates
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2) {
|
|
return new ImmutableCollections.Set12<>(e1, e2);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing three elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2, E e3) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing four elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @param e4 the fourth element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2, E e3, E e4) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3, e4);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing five elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @param e4 the fourth element
|
|
* @param e5 the fifth element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing six elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @param e4 the fourth element
|
|
* @param e5 the fifth element
|
|
* @param e6 the sixth element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
|
|
e6);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing seven elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @param e4 the fourth element
|
|
* @param e5 the fifth element
|
|
* @param e6 the sixth element
|
|
* @param e7 the seventh element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
|
|
e6, e7);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing eight elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @param e4 the fourth element
|
|
* @param e5 the fifth element
|
|
* @param e6 the sixth element
|
|
* @param e7 the seventh element
|
|
* @param e8 the eighth element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
|
|
e6, e7, e8);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing nine elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @param e4 the fourth element
|
|
* @param e5 the fifth element
|
|
* @param e6 the sixth element
|
|
* @param e7 the seventh element
|
|
* @param e8 the eighth element
|
|
* @param e9 the ninth element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
|
|
e6, e7, e8, e9);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing ten elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param e1 the first element
|
|
* @param e2 the second element
|
|
* @param e3 the third element
|
|
* @param e4 the fourth element
|
|
* @param e5 the fifth element
|
|
* @param e6 the sixth element
|
|
* @param e7 the seventh element
|
|
* @param e8 the eighth element
|
|
* @param e9 the ninth element
|
|
* @param e10 the tenth element
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
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) {
|
|
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
|
|
e6, e7, e8, e9, e10);
|
|
}
|
|
|
|
/**
|
|
* Returns an unmodifiable set containing an arbitrary number of elements.
|
|
* See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
|
|
*
|
|
* @apiNote
|
|
* This method also accepts a single array as an argument. The element type of
|
|
* the resulting set will be the component type of the array, and the size of
|
|
* the set will be equal to the length of the array. To create a set with
|
|
* a single element that is an array, do the following:
|
|
*
|
|
* <pre>{@code
|
|
* String[] array = ... ;
|
|
* Set<String[]> list = Set.<String[]>of(array);
|
|
* }</pre>
|
|
*
|
|
* This will cause the {@link Set#of(Object) Set.of(E)} method
|
|
* to be invoked instead.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param elements the elements to be contained in the set
|
|
* @return a {@code Set} containing the specified elements
|
|
* @throws IllegalArgumentException if there are any duplicate elements
|
|
* @throws NullPointerException if an element is {@code null} or if the array is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
@SafeVarargs
|
|
@SuppressWarnings("varargs")
|
|
static <E> Set<E> of(E... elements) {
|
|
switch (elements.length) { // implicit null check of elements
|
|
case 0:
|
|
@SuppressWarnings("unchecked")
|
|
var set = (Set<E>) ImmutableCollections.EMPTY_SET;
|
|
return set;
|
|
case 1:
|
|
return new ImmutableCollections.Set12<>(elements[0]);
|
|
case 2:
|
|
return new ImmutableCollections.Set12<>(elements[0], elements[1]);
|
|
default:
|
|
return new ImmutableCollections.SetN<>(elements);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns an <a href="#unmodifiable">unmodifiable Set</a> containing the elements
|
|
* of the given Collection. The given Collection must not be null, and it must not
|
|
* contain any null elements. If the given Collection contains duplicate elements,
|
|
* an arbitrary element of the duplicates is preserved. If the given Collection is
|
|
* subsequently modified, the returned Set will not reflect such modifications.
|
|
*
|
|
* @implNote
|
|
* If the given Collection is an <a href="#unmodifiable">unmodifiable Set</a>,
|
|
* calling copyOf will generally not create a copy.
|
|
*
|
|
* @param <E> the {@code Set}'s element type
|
|
* @param coll a {@code Collection} from which elements are drawn, must be non-null
|
|
* @return a {@code Set} containing the elements of the given {@code Collection}
|
|
* @throws NullPointerException if coll is null, or if it contains any nulls
|
|
* @since 10
|
|
*/
|
|
@SuppressWarnings("unchecked")
|
|
static <E> Set<E> copyOf(Collection<? extends E> coll) {
|
|
if (coll instanceof ImmutableCollections.AbstractImmutableSet) {
|
|
return (Set<E>)coll;
|
|
} else {
|
|
return (Set<E>)Set.of(new HashSet<>(coll).toArray());
|
|
}
|
|
}
|
|
}
|