/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * This file is available under and governed by the GNU General Public * License version 2 only, as published by the Free Software Foundation. * However, the following notice accompanied the original version of this * file: * * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at * http://creativecommons.org/publicdomain/zero/1.0/ */ package java.util.concurrent; import java.util.Collection; import java.util.Set; import java.util.AbstractSet; import java.util.Iterator; import java.util.Spliterator; import java.util.Spliterators; import java.util.function.Predicate; import java.util.function.Consumer; /** * A {@link java.util.Set} that uses an internal {@link CopyOnWriteArrayList} * for all of its operations. Thus, it shares the same basic properties: *
Sample Usage. The following code sketch uses a * copy-on-write set to maintain a set of Handler objects that * perform some action upon state updates. * *
{@code * class Handler { void handle(); ... } * * class X { * private final CopyOnWriteArraySet* *handlers * = new CopyOnWriteArraySet (); * public void addHandler(Handler h) { handlers.add(h); } * * private long internalState; * private synchronized void changeState() { internalState = ...; } * * public void update() { * changeState(); * for (Handler handler : handlers) * handler.handle(); * } * }}
This class is a member of the
*
* Java Collections Framework.
*
* @see CopyOnWriteArrayList
* @since 1.5
* @author Doug Lea
* @param The returned array will be "safe" in that no references to it
* are maintained by this set. (In other words, this method must
* allocate a new array even if this set is backed by an array).
* The caller is thus free to modify the returned array.
*
* This method acts as bridge between array-based and collection-based
* APIs.
*
* @return an array containing all the elements in this set
*/
public Object[] toArray() {
return al.toArray();
}
/**
* Returns an array containing all of the elements in this set; the
* runtime type of the returned array is that of the specified array.
* If the set fits in the specified array, it is returned therein.
* Otherwise, a new array is allocated with the runtime type of the
* specified array and the size of this set.
*
* If this set fits in the specified array with room to spare
* (i.e., the array has more elements than this set), the element in
* the array immediately following the end of the set is set to
* {@code null}. (This is useful in determining the length of this
* set only if the caller knows that this set does not contain
* any null elements.)
*
* If this set makes any guarantees as to what order its elements
* are returned by its iterator, this method must return the elements
* in the same order.
*
* Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
* Suppose {@code x} is a set known to contain only strings.
* The following code can be used to dump the set into a newly allocated
* array of {@code String}:
*
* The returned iterator provides a snapshot of the state of the set
* when the iterator was constructed. No synchronization is needed while
* traversing the iterator. The iterator does NOT support the
* {@code remove} method.
*
* @return an iterator over the elements in this set
*/
public Iterator The {@code Spliterator} reports {@link Spliterator#IMMUTABLE},
* {@link Spliterator#DISTINCT}, {@link Spliterator#SIZED}, and
* {@link Spliterator#SUBSIZED}.
*
* The spliterator provides a snapshot of the state of the set
* when the spliterator was constructed. No synchronization is needed while
* operating on the spliterator.
*
* @return a {@code Spliterator} over the elements in this set
* @since 1.8
*/
public Spliterator(o==null ? e==null : o.equals(e))
.
*
* @param o element whose presence in this set is to be tested
* @return {@code true} if this set contains the specified element
*/
public boolean contains(Object o) {
return al.contains(o);
}
/**
* Returns an array containing all of the elements in this set.
* If this set makes any guarantees as to what order its elements
* are returned by its iterator, this method must return the
* elements in the same order.
*
* {@code String[] y = x.toArray(new String[0]);}
*
* Note that {@code toArray(new Object[0])} is identical in function to
* {@code toArray()}.
*
* @param a the array into which the elements of this set are to be
* stored, if it is big enough; otherwise, a new array of the same
* runtime type is allocated for this purpose.
* @return an array containing all the elements in this set
* @throws ArrayStoreException if the runtime type of the specified array
* is not a supertype of the runtime type of every element in this
* set
* @throws NullPointerException if the specified array is null
*/
public (o==null ? e==null : o.equals(e))
,
* if this set contains such an element. Returns {@code true} if
* this set contained the element (or equivalently, if this set
* changed as a result of the call). (This set will not contain the
* element once the call returns.)
*
* @param o object to be removed from this set, if present
* @return {@code true} if this set contained the specified element
*/
public boolean remove(Object o) {
return al.remove(o);
}
/**
* Adds the specified element to this set if it is not already present.
* More formally, adds the specified element {@code e} to this set if
* the set contains no element {@code e2} such that
* (e==null ? e2==null : e.equals(e2))
.
* If this set already contains the element, the call leaves the set
* unchanged and returns {@code false}.
*
* @param e element to be added to this set
* @return {@code true} if this set did not already contain the specified
* element
*/
public boolean add(E e) {
return al.addIfAbsent(e);
}
/**
* Returns {@code true} if this set contains all of the elements of the
* specified collection. If the specified collection is also a set, this
* method returns {@code true} if it is a subset of this set.
*
* @param c collection to be checked for containment in this set
* @return {@code true} if this set contains all of the elements of the
* specified collection
* @throws NullPointerException if the specified collection is null
* @see #contains(Object)
*/
public boolean containsAll(Collection> c) {
return al.containsAll(c);
}
/**
* Adds all of the elements in the specified collection to this set if
* they're not already present. If the specified collection is also a
* set, the {@code addAll} operation effectively modifies this set so
* that its value is the union of the two sets. The behavior of
* this operation is undefined if the specified collection is modified
* while the operation is in progress.
*
* @param c collection containing elements to be added to this set
* @return {@code true} if this set changed as a result of the call
* @throws NullPointerException if the specified collection is null
* @see #add(Object)
*/
public boolean addAll(Collection extends E> c) {
return al.addAllAbsent(c) > 0;
}
/**
* Removes from this set all of its elements that are contained in the
* specified collection. If the specified collection is also a set,
* this operation effectively modifies this set so that its value is the
* asymmetric set difference of the two sets.
*
* @param c collection containing elements to be removed from this set
* @return {@code true} if this set changed as a result of the call
* @throws ClassCastException if the class of an element of this set
* is incompatible with the specified collection (optional)
* @throws NullPointerException if this set contains a null element and the
* specified collection does not permit null elements (optional),
* or if the specified collection is null
* @see #remove(Object)
*/
public boolean removeAll(Collection> c) {
return al.removeAll(c);
}
/**
* Retains only the elements in this set that are contained in the
* specified collection. In other words, removes from this set all of
* its elements that are not contained in the specified collection. If
* the specified collection is also a set, this operation effectively
* modifies this set so that its value is the intersection of the
* two sets.
*
* @param c collection containing elements to be retained in this set
* @return {@code true} if this set changed as a result of the call
* @throws ClassCastException if the class of an element of this set
* is incompatible with the specified collection (optional)
* @throws NullPointerException if this set contains a null element and the
* specified collection does not permit null elements (optional),
* or if the specified collection is null
* @see #remove(Object)
*/
public boolean retainAll(Collection> c) {
return al.retainAll(c);
}
/**
* Returns an iterator over the elements contained in this set
* in the order in which these elements were added.
*
*