Java AtomicReferenceArray compareAndExchange()用法及代碼示例

如果AtomicReferenceArray對象的索引i處的當前值(稱為見證值)等於期望值，則使用AtomicReferenceArray類的compareAndExchange()方法原子地將AtomicReferenceArray的索引i的值設置為newValue。此方法將返回見證值，該值將與期望值相同。此方法使用讀取的內存語義來處理操作，就像將該變量聲明為volatile一樣。

用法:

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

參數：此方法接受：

i這是執行操作的AtomicReferenceArray的索引，
expectedValue 這是期望值，
newValue 這是要設置的新值。

返回值：此方法返回見證值，如果成功，它將與期望值相同。

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

// Java program to demonstrate 
// compareAndExchange() method 
  
import java.util.concurrent.atomic.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // create an atomic reference object. 
        AtomicReferenceArray<Integer> ref 
            = new AtomicReferenceArray<Integer>(3); 
  
        // set some value 
        ref.set(0, 1234); 
        ref.set(1, 4322); 
  
        // apply compareAndExchange() 
        int oldV1 
            = ref.compareAndExchange(0, 1234, 8913); 
        int oldV2 
            = ref.compareAndExchange(1, 4322, 6543); 
  
        // print 
        System.out.println("Old value at index 0:"
                           + oldV1); 
        System.out.println("Old value at index 1:"
                           + oldV2); 
    } 
}

輸出：

程序2:

// Java program to demonstrate 
// compareAndExchange() method 
  
import java.util.concurrent.atomic.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // create an atomic reference object. 
        AtomicReferenceArray<String> ref 
            = new AtomicReferenceArray<String>(3); 
  
        // set some value 
        ref.set(0, "GFG"); 
        ref.set(1, "JS"); 
  
        // apply compareAndExchange() 
        String oldV1 
            = ref.compareAndExchange( 
                0, "GFG", 
                "GEEKS FOR GEEKS"); 
        String oldV2 
            = ref.compareAndExchange( 
                1, "JS", 
                "JAVA SCRIPT"); 
  
        // print 
        System.out.println("Old value at index 0:"
                           + oldV1); 
        System.out.println("New value at index 0:"
                           + ref.get(0)); 
        System.out.println("Old value at index 1:"
                           + oldV2); 
        System.out.println("New value at index 1:"
                           + ref.get(1)); 
    } 
}

輸出：

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

相關用法

注：本文由純淨天空篩選整理自AmanSingh2210大神的英文原創作品 AtomicReferenceArray compareAndExchange() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。