Java AtomicReferenceArray weakCompareAndSetVolatile()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AtomicReferenceArray類的weakCompareAndSetVolatile()方法以原子方式將AtomicReferenceArray的索引i處的元素值設置為newValue到newValue。此方法使用VarHandle.weakCompareAndSet(java.lang.Object…)指定的具有 memory 效應的值來更新該值。如果成功將AtomicRefrence設置為新值，則此方法返回true。

用法:

public final boolean
       weakCompareAndSetVolatile(int i,
                                 E expectedValue,
                                 E newValue)

參數：此方法接受i(它是AtomicReferenceArray的索引)來執行操作，ExpectedValue是期望值，而newValue是要設置的新值。

返回值：如果成功，則此方法返回true。

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

// Java program to demonstrate AtomicReferenceArray 
// weakCompareAndSetVolatile() method 
  
import java.util.concurrent.atomic.AtomicReferenceArray; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // create an atomic reference object. 
        AtomicReferenceArray<Double> ref 
            = new AtomicReferenceArray<Double>(5); 
  
        // set some value 
        ref.set(1, 1234.00); 
        ref.set(0, 2234.00); 
        ref.set(2, 3234.00); 
  
        // apply weakCompareAndSetVolatile() 
        boolean result 
            = ref.weakCompareAndSetVolatile(1, 124.00, 
                                            234.32); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
  
        System.out.println("Value of index 1 = "
                           + ref.get(1)); 
    } 
}

輸出：

程序2:

// Java program to demonstrate AtomicReferenceArray 
// weakCompareAndSetVolatile() method 
  
import java.util.concurrent.atomic.AtomicReferenceArray; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // create an atomic reference object. 
        AtomicReferenceArray<String> ref 
            = new AtomicReferenceArray<String>(5); 
  
        // set some value 
        ref.set(0, "AMANDIP"); 
        ref.set(1, "AMAN"); 
  
        // apply weakCompareAndSetVolatile() 
        boolean result 
            = ref.weakCompareAndSetVolatile( 
                0, 
                "AMARDIP", 
                "AMAR"); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
  
        System.out.println("Value of index 0 = "
                           + ref.get(0)); 
    } 
}

輸出：

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

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