AtomicInteger类

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这一讲，主要讲讲AtomicInteger类，此类同样是Number的子类，同时实现 Serializable。

重点内容

属性：

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

静态代码块：

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

构造方法

public AtomicInteger() {    }public AtomicInteger(int initialValue) {        value = initialValue;    }

对象方法：

 public final int get() {        return value;    }public final void set(int newValue) {        value = newValue;    }public final void lazySet(int newValue) {        unsafe.putOrderedInt(this, valueOffset, newValue);    }public final int getAndSet(int newValue) {        for (;;) {            int current = get();            if (compareAndSet(current, newValue))                return current;        }    }public final boolean compareAndSet(int expect, int update) {        return unsafe.compareAndSwapInt(this, valueOffset, expect, update);    }public final boolean weakCompareAndSet(int expect, int update) {        return unsafe.compareAndSwapInt(this, valueOffset, expect, update);    }public final int getAndIncrement() {        for (;;) {            int current = get();            int next = current + 1;            if (compareAndSet(current, next))                return current;        }    }public final int getAndDecrement() {        for (;;) {            int current = get();            int next = current - 1;            if (compareAndSet(current, next))                return current;        }    }public final int getAndAdd(int delta) {        for (;;) {            int current = get();            int next = current + delta;            if (compareAndSet(current, next))                return current;        }    }public final int incrementAndGet() {        for (;;) {            int current = get();            int next = current + 1;            if (compareAndSet(current, next))                return next;        }    }public final int decrementAndGet() {        for (;;) {            int current = get();            int next = current - 1;            if (compareAndSet(current, next))                return next;        }    }public final int addAndGet(int delta) {        for (;;) {            int current = get();            int next = current + delta;            if (compareAndSet(current, next))                return next;        }    }public String toString() {        return Integer.toString(get());    }public int intValue() {        return get();    }public long longValue() {        return (long)get();    }public float floatValue() {        return (float)get();    }public double doubleValue() {        return (double)get();    }

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