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/*
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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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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/publicdomain/zero/1.0/
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*/
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package java.util.concurrent.atomic;
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/**
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* A {@code boolean} value that may be updated atomically. See the
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* {@link java.util.concurrent.atomic} package specification for
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* description of the properties of atomic variables. An
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* {@code AtomicBoolean} is used in applications such as atomically
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* updated flags, and cannot be used as a replacement for a
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* {@link java.lang.Boolean}.
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*
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* @since 1.5
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* @author Doug Lea
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*/
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public class AtomicBoolean implements java.io.Serializable {
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private static final long serialVersionUID = 4654671469794556979L;
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private volatile int value;
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/**
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* Creates a new {@code AtomicBoolean} with the given initial value.
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*
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* @param initialValue the initial value
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*/
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public AtomicBoolean(boolean initialValue) {
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value = initialValue ? 1 : 0;
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}
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/**
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* Creates a new {@code AtomicBoolean} with initial value {@code false}.
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*/
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public AtomicBoolean() {
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}
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/**
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* Returns the current value.
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*
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* @return the current value
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*/
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public final boolean get() {
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return value != 0;
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}
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/**
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* Atomically sets the value to the given updated value
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* if the current value {@code ==} the expected value.
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*
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* @param expect the expected value
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* @param update the new value
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* @return true if successful. False return indicates that
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* the actual value was not equal to the expected value.
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*/
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public final boolean compareAndSet(boolean expect, boolean update) {
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int e = expect ? 1 : 0;
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int u = update ? 1 : 0;
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if (this.value == e) {
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this.value = u;
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return true;
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} else {
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return false;
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}
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}
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/**
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* Atomically sets the value to the given updated value
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* if the current value {@code ==} the expected value.
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*
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* <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
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* and does not provide ordering guarantees, so is only rarely an
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* appropriate alternative to {@code compareAndSet}.
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*
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* @param expect the expected value
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* @param update the new value
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* @return true if successful.
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*/
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public boolean weakCompareAndSet(boolean expect, boolean update) {
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return compareAndSet(expect, update);
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}
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/**
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* Unconditionally sets to the given value.
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*
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* @param newValue the new value
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*/
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public final void set(boolean newValue) {
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value = newValue ? 1 : 0;
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}
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/**
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* Eventually sets to the given value.
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*
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* @param newValue the new value
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* @since 1.6
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*/
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public final void lazySet(boolean newValue) {
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set(newValue);
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}
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/**
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* Atomically sets to the given value and returns the previous value.
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*
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* @param newValue the new value
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* @return the previous value
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*/
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public final boolean getAndSet(boolean newValue) {
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for (;;) {
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boolean current = get();
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if (compareAndSet(current, newValue))
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return current;
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}
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}
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/**
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* Returns the String representation of the current value.
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* @return the String representation of the current value.
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*/
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public String toString() {
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return Boolean.toString(get());
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}
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}
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