Java AtomicReferenceArray weakCompareAndSetPlain()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weakCompareAndSetPlain()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set的內存語義更新索引i的值，就像索引i的變量聲明為非易失性和非最終值一樣。如果成功設置新值，則此方法返回true。

用法:

public final boolean weakCompareAndSetPlain(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weakCompareAndSetPlain()方法：
程序1:

// Java program to demonstrate AtomicReferenceArray 
// weakCompareAndSetPlain() method 
  
import java.util.concurrent.atomic.AtomicReferenceArray; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // create an atomic reference object. 
        AtomicReferenceArray<Integer> ref 
            = new AtomicReferenceArray<Integer>(5); 
  
        // set some value 
        ref.set(0, 321); 
        ref.set(1, 123); 
        ref.set(2, 322); 
  
        // apply weakCompareAndSetPlain() 
        boolean result 
            = ref.weakCompareAndSetPlain( 
                0, 124, 
                234); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
  
        System.out.println("Value of index 0 = "
                           + ref.get(1)); 
    } 
}

輸出：

程序2:

// Java program to demonstrate AtomicReferenceArray 
// weakCompareAndSetPlain() method 
  
import java.util.concurrent.atomic.AtomicReferenceArray; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // create an atomic reference object.c 
        AtomicReferenceArray<String> ref 
            = new AtomicReferenceArray<String>(5); 
  
        // set some value 
        ref.set(0, "C"); 
        ref.set(1, "JAVA"); 
        ref.set(2, "JS"); 
        ref.set(3, "C++"); 
        ref.set(4, "C"); 
  
        // apply weakCompareAndSetVolatile() 
        boolean result 
            = ref.weakCompareAndSetVolatile( 
                4, "C", 
                "PYTHON"); 
  
        // print value 
        System.out.println("Setting new value"
                           + " is successful = "
                           + result); 
  
        System.out.println("Value of index 4 = "
                           + ref.get(4)); 
    } 
}

輸出：

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

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