/*
* 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.atomic;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
/**
* A {@code boolean} value that may be updated atomically. See the
* {@link VarHandle} specification for descriptions of the properties
* of atomic accesses. An {@code AtomicBoolean} is used in
* applications such as atomically updated flags, and cannot be used
* as a replacement for a {@link java.lang.Boolean}.
*
* @since 1.5
* @author Doug Lea
*/
public class AtomicBoolean implements java.io.Serializable {
private static final long serialVersionUID = 4654671469794556979L;
private static final VarHandle VALUE;
static {
try {
MethodHandles.Lookup l = MethodHandles.lookup();
VALUE = l.findVarHandle(AtomicBoolean.class, "value", int.class);
} catch (ReflectiveOperationException e) {
throw new Error(e);
}
}
private volatile int value;
/**
* Creates a new {@code AtomicBoolean} with the given initial value.
*
* @param initialValue the initial value
*/
public AtomicBoolean(boolean initialValue) {
value = initialValue ? 1 : 0;
}
/**
* Creates a new {@code AtomicBoolean} with initial value {@code false}.
*/
public AtomicBoolean() {
}
/**
* Returns the current value,
* with memory effects as specified by {@link VarHandle#getVolatile}.
*
* @return the current value
*/
public final boolean get() {
return value != 0;
}
/**
* Atomically sets the value to {@code newValue}
* if the current value {@code == expectedValue},
* with memory effects as specified by {@link VarHandle#compareAndSet}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return {@code true} if successful. False return indicates that
* the actual value was not equal to the expected value.
*/
public final boolean compareAndSet(boolean expectedValue, boolean newValue) {
return VALUE.compareAndSet(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0));
}
/**
* Possibly atomically sets the value to {@code newValue}
* if the current value {@code == expectedValue},
* with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
*
* @deprecated This method has plain memory effects but the method
* name implies volatile memory effects (see methods such as
* {@link #compareAndExchange} and {@link #compareAndSet}). To avoid
* confusion over plain or volatile memory effects it is recommended that
* the method {@link #weakCompareAndSetPlain} be used instead.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return {@code true} if successful
* @see #weakCompareAndSetPlain
*/
@Deprecated(since="9")
public boolean weakCompareAndSet(boolean expectedValue, boolean newValue) {
return VALUE.weakCompareAndSetPlain(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0));
}
/**
* Possibly atomically sets the value to {@code newValue}
* if the current value {@code == expectedValue},
* with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return {@code true} if successful
* @since 9
*/
public boolean weakCompareAndSetPlain(boolean expectedValue, boolean newValue) {
return VALUE.weakCompareAndSetPlain(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0));
}
/**
* Sets the value to {@code newValue},
* with memory effects as specified by {@link VarHandle#setVolatile}.
*
* @param newValue the new value
*/
public final void set(boolean newValue) {
value = newValue ? 1 : 0;
}
/**
* Sets the value to {@code newValue},
* with memory effects as specified by {@link VarHandle#setRelease}.
*
* @param newValue the new value
* @since 1.6
*/
public final void lazySet(boolean newValue) {
VALUE.setRelease(this, (newValue ? 1 : 0));
}
/**
* Atomically sets the value to {@code newValue} and returns the old value,
* with memory effects as specified by {@link VarHandle#getAndSet}.
*
* @param newValue the new value
* @return the previous value
*/
public final boolean getAndSet(boolean newValue) {
return (int)VALUE.getAndSet(this, (newValue ? 1 : 0)) != 0;
}
/**
* Returns the String representation of the current value.
* @return the String representation of the current value
*/
public String toString() {
return Boolean.toString(get());
}
// jdk9
/**
* Returns the current value, with memory semantics of reading as
* if the variable was declared non-{@code volatile}.
*
* @return the value
* @since 9
*/
public final boolean getPlain() {
return (int)VALUE.get(this) != 0;
}
/**
* Sets the value to {@code newValue}, with memory semantics
* of setting as if the variable was declared non-{@code volatile}
* and non-{@code final}.
*
* @param newValue the new value
* @since 9
*/
public final void setPlain(boolean newValue) {
VALUE.set(this, newValue ? 1 : 0);
}
/**
* Returns the current value,
* with memory effects as specified by {@link VarHandle#getOpaque}.
*
* @return the value
* @since 9
*/
public final boolean getOpaque() {
return (int)VALUE.getOpaque(this) != 0;
}
/**
* Sets the value to {@code newValue},
* with memory effects as specified by {@link VarHandle#setOpaque}.
*
* @param newValue the new value
* @since 9
*/
public final void setOpaque(boolean newValue) {
VALUE.setOpaque(this, newValue ? 1 : 0);
}
/**
* Returns the current value,
* with memory effects as specified by {@link VarHandle#getAcquire}.
*
* @return the value
* @since 9
*/
public final boolean getAcquire() {
return (int)VALUE.getAcquire(this) != 0;
}
/**
* Sets the value to {@code newValue},
* with memory effects as specified by {@link VarHandle#setRelease}.
*
* @param newValue the new value
* @since 9
*/
public final void setRelease(boolean newValue) {
VALUE.setRelease(this, newValue ? 1 : 0);
}
/**
* Atomically sets the value to {@code newValue} if the current value,
* referred to as the <em>witness value</em>, {@code == expectedValue},
* with memory effects as specified by
* {@link VarHandle#compareAndExchange}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return the witness value, which will be the same as the
* expected value if successful
* @since 9
*/
public final boolean compareAndExchange(boolean expectedValue, boolean newValue) {
return (int)VALUE.compareAndExchange(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0)) != 0;
}
/**
* Atomically sets the value to {@code newValue} if the current value,
* referred to as the <em>witness value</em>, {@code == expectedValue},
* with memory effects as specified by
* {@link VarHandle#compareAndExchangeAcquire}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return the witness value, which will be the same as the
* expected value if successful
* @since 9
*/
public final boolean compareAndExchangeAcquire(boolean expectedValue, boolean newValue) {
return (int)VALUE.compareAndExchangeAcquire(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0)) != 0;
}
/**
* Atomically sets the value to {@code newValue} if the current value,
* referred to as the <em>witness value</em>, {@code == expectedValue},
* with memory effects as specified by
* {@link VarHandle#compareAndExchangeRelease}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return the witness value, which will be the same as the
* expected value if successful
* @since 9
*/
public final boolean compareAndExchangeRelease(boolean expectedValue, boolean newValue) {
return (int)VALUE.compareAndExchangeRelease(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0)) != 0;
}
/**
* Possibly atomically sets the value to {@code newValue} if the current
* value {@code == expectedValue},
* with memory effects as specified by
* {@link VarHandle#weakCompareAndSet}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return {@code true} if successful
* @since 9
*/
public final boolean weakCompareAndSetVolatile(boolean expectedValue, boolean newValue) {
return VALUE.weakCompareAndSet(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0));
}
/**
* Possibly atomically sets the value to {@code newValue} if the current
* value {@code == expectedValue},
* with memory effects as specified by
* {@link VarHandle#weakCompareAndSetAcquire}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return {@code true} if successful
* @since 9
*/
public final boolean weakCompareAndSetAcquire(boolean expectedValue, boolean newValue) {
return VALUE.weakCompareAndSetAcquire(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0));
}
/**
* Possibly atomically sets the value to {@code newValue} if the current
* value {@code == expectedValue},
* with memory effects as specified by
* {@link VarHandle#weakCompareAndSetRelease}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return {@code true} if successful
* @since 9
*/
public final boolean weakCompareAndSetRelease(boolean expectedValue, boolean newValue) {
return VALUE.weakCompareAndSetRelease(this,
(expectedValue ? 1 : 0),
(newValue ? 1 : 0));
}
}