Java中的 AtomicReference weakCompareAndSet() 方法及示例

AtomicReference类的weakCompareAndSet()方法用于将 AtomicReference 的值自动设置为 newValue，如果当前值等于作为参数传递的 expectedValue。此方法使用读取的内存语义更新值，就好像变量被声明为 volatile 类型的变量一样。如果为 AtomicReference 设置新值成功，则此方法返回 true。

句法：

public final boolean weakCompareAndSet(V expectedValue,
                                       V newValue)

参数：此方法接受期望值和newValue ，这是要设置的新值。

返回值：如果成功，此方法返回true 。

下面的程序说明了weakCompareAndSet() 方法：
方案一：

// Java program to demonstrate
// AtomicReference.weakCompareAndSet() method
  
import java.util.concurrent.atomic.AtomicReference;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create an atomic reference object
        // which stores Integer.
        AtomicReference ref
            = new AtomicReference();
  
        // set some value
        ref.set(999);
  
        // apply weakCompareAndSet()
        boolean result
            = ref.weakCompareAndSet(999,
                                    999999);
  
        // print value
        System.out.println("Setting new value"
                           + " is successful = "
                           + result);
        System.out.println("New Value = "
                           + ref.get());
    }
}

输出：

Setting new value is successful = false
New Value = 999

方案二：

// Java program to demonstrate
// AtomicReference.weakCompareAndSet() method
  
import java.util.concurrent.atomic.AtomicReference;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create an atomic reference object
        // which stores String.
        AtomicReference ref
            = new AtomicReference();
  
        // set some value
        ref.set("GEEKS FOR GEEKS");
  
        // apply weakCompareAndSet()
        ref.weakCompareAndSet("GEEKS FOR GEEKS",
                              "GFG");
  
        // print value
        System.out.println("Value  = "
                           + ref.get());
    }
}

输出：

Value  = GFG

参考资料： https: Java/util/concurrent/atomic/AtomicReference.html#weakCompareAndSet(V, V)