AtomicInteger实现

无锁操作常见场景

atomic包内的类经常使用无锁操作

AtomicInteger是非常典型的一种

   private static final Unsafe unsafe = Unsafe.getUnsafe();    private static final long valueOffset;    static {        try {            valueOffset = unsafe.objectFieldOffset                (AtomicInteger.class.getDeclaredField("value"));        } catch (Exception ex) { throw new Error(ex); }    }    private volatile int value;

无锁增加操作实现 JDK1.7

public final int getAndDecrement() {      for (;;) {          int current = get();          int next = current - 1;          if (compareAndSet(current, next))              return current;      }  }

JDK1.8

public final int getAndAddInt(Object o, long offset, int delta) {    int v;    do {        v = getIntVolatile(o, offset);    } while (!compareAndSwapInt(o, offset, v, v + delta));    return v;}