Java AtomicReference weakCompareAndSetVolatile()用法及代码示例

如果当前值等于作为参数传递的ExpectedValue，则使用AtomicReference类的weakCompareAndSetVolatile()方法为AtomicReference原子地将值设置为newValue。此方法使用VarHandle.weakCompareAndSet(java.lang.Object…)指定的具有 memory 效应的值来更新该值。如果成功将AtomicRefrence设置为新值，则此方法返回true。

用法:

public final boolean 
       weakCompareAndSetVolatile(V expectedValue,
                                 V newValue)

参数：该方法接受ExpectedValue(期望值)和newValue(新值)来设置新值。

返回值：如果成功，则此方法返回true。

以下示例程序旨在说明weakCompareAndSetVolatile()方法：
程序1:

// Java program to demonstrate 
// AtomicReference.weakCompareAndSetVolatile() method 
  
import java.util.concurrent.atomic.AtomicReference; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // create an atomic reference object. 
        AtomicReference<Double> ref 
            = new AtomicReference<Double>(); 
  
        // set some value 
        ref.set(1234.00); 
  
        // apply weakCompareAndSetVolatile() 
        boolean result 
            = ref.weakCompareAndSetVolatile(124.00, 
                                            234.32); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
  
        System.out.println("Value = " + ref.get()); 
    } 
}

输出：

程序2:

// Java program to demonstrate 
// AtomicReference.weakCompareAndSetVolatile() 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<String> ref = new AtomicReference<String>(); 
  
        // set some value 
        ref.set("GFG"); 
  
        // apply weakCompareAndSetVolatile() 
        boolean result 
            = ref.weakCompareAndSetVolatile( 
                "GFG", 
                "GEEKS FOR GEEKS"); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
        System.out.println("Value  = " + ref.get()); 
    } 
}

输出：

参考文献： https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/atomic/AtomicReference.html#weakCompareAndSetVolatile(V, V)

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