Java AtomicReference weakCompareAndSetAcquire()用法及代碼示例

如果當前值等於作為參數傳遞的ExpectedValue，則使用AtomicReference類的weakCompareAndSetAcquire()方法為AtomicReference原子地將值設置為newValue。此方法以與memory_order_acquire排序兼容的內存排序效果更新該值。如果成功將AtomicRefrence設置為新值，則此方法返回true。

用法:

public final boolean
 weakCompareAndSetAcquire(V expectedValue,
                          V newValue)

參數：該方法接受ExpectedValue(期望值)和newValue(新值)來設置新值。

返回值：如果成功，則此方法返回true。

以下示例程序旨在說明weakCompareAndSetAcquire()方法：
程序1:

// Java program to demonstrate 
// AtomicReference.weakCompareAndSetAcquire() 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<Long> ref 
            = new AtomicReference<Long>(); 
  
        // set some value 
        ref.set(11111111L); 
  
        // apply weakCompareAndSetAcquire() 
        boolean result 
            = ref.weakCompareAndSetAcquire( 
                1111111111111L, 
                999999L); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
        System.out.println("Value = " + ref.get()); 
    } 
}

輸出：

程序2:

// Java program to demonstrate 
// AtomicReference.weakCompareAndSetAcquire() 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("WELCOME TO GEEKS FOR GEEKS"); 
  
        // apply weakCompareAndSetAcquire() 
        boolean result 
            = ref.weakCompareAndSetAcquire( 
                "WELCOME TO GEEKS FOR GEEKS", 
                "WELCOLME GEEKS"); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
        System.out.println("Value  = " + ref.get()); 
    } 
}

輸出：

參考文獻： https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/atomic/AtomicReference.html#weakCompareAndSetAcquire(V, V)

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