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[代码资源] AtomicInteger类

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发表于 2019-3-23 16:04 |只看该作者 |正序浏览

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AtomicInteger类

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();
}
---------------------
作者：feyshine
来源：CSDN