AtomicReference

佚名 6年前 (2019-04-21) 随笔 1855人围观抢沙发百度已收录

public class AtomicReference<V> implements java.io.Serializable {
    private static final long serialVersionUID = -1848883965231344442L;

    private static final Unsafe unsafe = Unsafe.getUnsafe();
    private static final long valueOffset;

    static {
        try {
            valueOffset = unsafe.objectFieldOffset(AtomicReference.class.getDeclaredField("value"));
        } catch (Exception ex) { throw new Error(ex); }
    }

    private volatile V value;

    public AtomicReference(V initialValue) {
        value = initialValue;
    }

    public AtomicReference() {
    }

    public final V get() {
        return value;
    }

    public final void set(V newValue) {
        value = newValue;
    }

    public final void lazySet(V newValue) {
        unsafe.putOrderedObject(this, valueOffset, newValue);
    }

    public final boolean compareAndSet(V expect, V update) {
        return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
    }

    public final boolean weakCompareAndSet(V expect, V update) {
        return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
    }

    @SuppressWarnings("unchecked")
    public final V getAndSet(V newValue) {
        return (V)unsafe.getAndSetObject(this, valueOffset, newValue);
    }

    public final V getAndUpdate(UnaryOperator<V> updateFunction) {
        V prev, next;
        do {
            prev = get();
            next = updateFunction.apply(prev);
        } while (!compareAndSet(prev, next));
        return prev;
    }

    public final V updateAndGet(UnaryOperator<V> updateFunction) {
        V prev, next;
        do {
            prev = get();
            next = updateFunction.apply(prev);
        } while (!compareAndSet(prev, next));
        return next;
    }

    public final V getAndAccumulate(V x,BinaryOperator<V> accumulatorFunction) {
        V prev, next;
        do {
            prev = get();
            next = accumulatorFunction.apply(prev, x);
        } while (!compareAndSet(prev, next));
        return prev;
    }

    public final V accumulateAndGet(V x,BinaryOperator<V> accumulatorFunction) {
        V prev, next;
        do {
            prev = get();
            next = accumulatorFunction.apply(prev, x);
        } while (!compareAndSet(prev, next));
        return next;
    }

    public String toString() {
        return String.valueOf(get());
    }
}