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AtomicBoolean.javaAPI DocJava SE 6 API3953Tue Jun 10 00:25:56 BST 2008java.util.concurrent.atomic

AtomicBoolean

public class AtomicBoolean extends Object implements Serializable
A {@code boolean} value that may be updated atomically. See the {@link java.util.concurrent.atomic} package specification for description of the properties of atomic variables. 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

Fields Summary
private static final long
serialVersionUID
private static final Unsafe
unsafe
private static final long
valueOffset
private volatile int
value
Constructors Summary
public AtomicBoolean(boolean initialValue)
Creates a new {@code AtomicBoolean} with the given initial value.

param
initialValue the initial value

        value = initialValue ? 1 : 0;
    
public AtomicBoolean()
Creates a new {@code AtomicBoolean} with initial value {@code false}.

    
Methods Summary
public final booleancompareAndSet(boolean expect, boolean update)
Atomically sets the value to the given updated value if the current value {@code ==} the expected value.

param
expect the expected value
param
update the new value
return
true if successful. False return indicates that the actual value was not equal to the expected value.

        int e = expect ? 1 : 0;
        int u = update ? 1 : 0;
        return unsafe.compareAndSwapInt(this, valueOffset, e, u);
    
public final booleanget()
Returns the current value.

return
the current value

        return value != 0;
    
public final booleangetAndSet(boolean newValue)
Atomically sets to the given value and returns the previous value.

param
newValue the new value
return
the previous value

        for (;;) {
            boolean current = get();
            if (compareAndSet(current, newValue))
                return current;
        }
    
public final voidlazySet(boolean newValue)
Eventually sets to the given value.

param
newValue the new value
since
1.6

        int v = newValue ? 1 : 0;
        unsafe.putOrderedInt(this, valueOffset, v);
    
public final voidset(boolean newValue)
Unconditionally sets to the given value.

param
newValue the new value

        value = newValue ? 1 : 0;
    
public java.lang.StringtoString()
Returns the String representation of the current value.

return
the String representation of the current value.

        return Boolean.toString(get());
    
public booleanweakCompareAndSet(boolean expect, boolean update)
Atomically sets the value to the given updated value if the current value {@code ==} the expected value.

May fail spuriously and does not provide ordering guarantees, so is only rarely an appropriate alternative to {@code compareAndSet}.

param
expect the expected value
param
update the new value
return
true if successful.

        int e = expect ? 1 : 0;
        int u = update ? 1 : 0;
        return unsafe.compareAndSwapInt(this, valueOffset, e, u);