361 lines
12 KiB
Java
361 lines
12 KiB
Java
/*
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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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import java.lang.invoke.MethodHandles;
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import java.lang.invoke.VarHandle;
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/**
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* A {@code boolean} value that may be updated atomically. See the
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* {@link VarHandle} specification for descriptions of the properties
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* of atomic accesses. An {@code AtomicBoolean} is used in
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* applications such as atomically updated flags, and cannot be used
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* as a replacement for a {@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 static final VarHandle VALUE;
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static {
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try {
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MethodHandles.Lookup l = MethodHandles.lookup();
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VALUE = l.findVarHandle(AtomicBoolean.class, "value", int.class);
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} catch (ReflectiveOperationException e) {
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throw new ExceptionInInitializerError(e);
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}
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}
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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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if (initialValue)
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value = 1;
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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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* with memory effects as specified by {@link VarHandle#getVolatile}.
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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 {@code newValue}
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* if the current value {@code == expectedValue},
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* with memory effects as specified by {@link VarHandle#compareAndSet}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return {@code 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 expectedValue, boolean newValue) {
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return VALUE.compareAndSet(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0));
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}
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/**
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* Possibly atomically sets the value to {@code newValue}
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* if the current value {@code == expectedValue},
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* with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
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*
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* @deprecated This method has plain memory effects but the method
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* name implies volatile memory effects (see methods such as
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* {@link #compareAndExchange} and {@link #compareAndSet}). To avoid
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* confusion over plain or volatile memory effects it is recommended that
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* the method {@link #weakCompareAndSetPlain} be used instead.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return {@code true} if successful
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* @see #weakCompareAndSetPlain
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*/
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@Deprecated(since="9")
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public boolean weakCompareAndSet(boolean expectedValue, boolean newValue) {
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return VALUE.weakCompareAndSetPlain(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0));
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}
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/**
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* Possibly atomically sets the value to {@code newValue}
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* if the current value {@code == expectedValue},
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* with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return {@code true} if successful
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* @since 9
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*/
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public boolean weakCompareAndSetPlain(boolean expectedValue, boolean newValue) {
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return VALUE.weakCompareAndSetPlain(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0));
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}
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/**
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* Sets the value to {@code newValue},
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* with memory effects as specified by {@link VarHandle#setVolatile}.
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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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* Sets the value to {@code newValue},
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* with memory effects as specified by {@link VarHandle#setRelease}.
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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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VALUE.setRelease(this, (newValue ? 1 : 0));
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}
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/**
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* Atomically sets the value to {@code newValue} and returns the old value,
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* with memory effects as specified by {@link VarHandle#getAndSet}.
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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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return (int)VALUE.getAndSet(this, (newValue ? 1 : 0)) != 0;
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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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// jdk9
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/**
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* Returns the current value, with memory semantics of reading as
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* if the variable was declared non-{@code volatile}.
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*
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* @return the value
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* @since 9
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*/
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public final boolean getPlain() {
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return (int)VALUE.get(this) != 0;
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}
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/**
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* Sets the value to {@code newValue}, with memory semantics
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* of setting as if the variable was declared non-{@code volatile}
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* and non-{@code final}.
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*
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* @param newValue the new value
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* @since 9
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*/
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public final void setPlain(boolean newValue) {
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VALUE.set(this, newValue ? 1 : 0);
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}
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/**
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* Returns the current value,
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* with memory effects as specified by {@link VarHandle#getOpaque}.
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*
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* @return the value
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* @since 9
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*/
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public final boolean getOpaque() {
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return (int)VALUE.getOpaque(this) != 0;
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}
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/**
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* Sets the value to {@code newValue},
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* with memory effects as specified by {@link VarHandle#setOpaque}.
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*
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* @param newValue the new value
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* @since 9
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*/
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public final void setOpaque(boolean newValue) {
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VALUE.setOpaque(this, newValue ? 1 : 0);
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}
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/**
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* Returns the current value,
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* with memory effects as specified by {@link VarHandle#getAcquire}.
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*
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* @return the value
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* @since 9
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*/
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public final boolean getAcquire() {
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return (int)VALUE.getAcquire(this) != 0;
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}
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/**
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* Sets the value to {@code newValue},
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* with memory effects as specified by {@link VarHandle#setRelease}.
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*
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* @param newValue the new value
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* @since 9
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*/
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public final void setRelease(boolean newValue) {
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VALUE.setRelease(this, newValue ? 1 : 0);
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}
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/**
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* Atomically sets the value to {@code newValue} if the current value,
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* referred to as the <em>witness value</em>, {@code == expectedValue},
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* with memory effects as specified by
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* {@link VarHandle#compareAndExchange}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return the witness value, which will be the same as the
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* expected value if successful
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* @since 9
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*/
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public final boolean compareAndExchange(boolean expectedValue, boolean newValue) {
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return (int)VALUE.compareAndExchange(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0)) != 0;
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}
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/**
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* Atomically sets the value to {@code newValue} if the current value,
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* referred to as the <em>witness value</em>, {@code == expectedValue},
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* with memory effects as specified by
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* {@link VarHandle#compareAndExchangeAcquire}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return the witness value, which will be the same as the
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* expected value if successful
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* @since 9
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*/
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public final boolean compareAndExchangeAcquire(boolean expectedValue, boolean newValue) {
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return (int)VALUE.compareAndExchangeAcquire(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0)) != 0;
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}
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/**
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* Atomically sets the value to {@code newValue} if the current value,
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* referred to as the <em>witness value</em>, {@code == expectedValue},
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* with memory effects as specified by
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* {@link VarHandle#compareAndExchangeRelease}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return the witness value, which will be the same as the
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* expected value if successful
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* @since 9
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*/
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public final boolean compareAndExchangeRelease(boolean expectedValue, boolean newValue) {
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return (int)VALUE.compareAndExchangeRelease(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0)) != 0;
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}
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/**
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* Possibly atomically sets the value to {@code newValue} if the current
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* value {@code == expectedValue},
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* with memory effects as specified by
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* {@link VarHandle#weakCompareAndSet}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return {@code true} if successful
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* @since 9
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*/
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public final boolean weakCompareAndSetVolatile(boolean expectedValue, boolean newValue) {
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return VALUE.weakCompareAndSet(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0));
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}
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/**
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* Possibly atomically sets the value to {@code newValue} if the current
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* value {@code == expectedValue},
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* with memory effects as specified by
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* {@link VarHandle#weakCompareAndSetAcquire}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return {@code true} if successful
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* @since 9
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*/
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public final boolean weakCompareAndSetAcquire(boolean expectedValue, boolean newValue) {
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return VALUE.weakCompareAndSetAcquire(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0));
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}
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/**
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* Possibly atomically sets the value to {@code newValue} if the current
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* value {@code == expectedValue},
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* with memory effects as specified by
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* {@link VarHandle#weakCompareAndSetRelease}.
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*
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* @param expectedValue the expected value
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* @param newValue the new value
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* @return {@code true} if successful
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* @since 9
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*/
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public final boolean weakCompareAndSetRelease(boolean expectedValue, boolean newValue) {
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return VALUE.weakCompareAndSetRelease(this,
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(expectedValue ? 1 : 0),
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(newValue ? 1 : 0));
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}
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}
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