Java AtomicLongArray compareAndSet()用法及代码示例

Java.util.concurrent.atomic.AtomicLongArray.compareAndSet()是Java中的一种内置方法，如果当前值等于预期值，则该方法原子地将元素设置在给定的更新值。此方法将索引值，期望值和更新值作为参数，并返回一个布尔值，说明该值是否已更新。

用法:

public final boolean compareAndSet(int i, long expect, long update)

参数：该函数接受三个参数：

i：要进行操作的索引。
expect：要检查的期望值是否等于当前值。
update：要更新的值。

返回值：该函数返回一个布尔值，说明该值是否已更新。如果成功，则返回true，否则返回false，指示当前值不等于期望值。

以下示例程序旨在说明上述方法：
示例1:

// Java program that demonstrates 
// the compareAndSet() function 
  
import java.util.concurrent.atomic.AtomicLongArray; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Initializing an array 
        long a[] = { 1, 2, 3, 4, 5 }; 
  
        // Initializing an AtomicLongArray with array a 
        AtomicLongArray arr = new AtomicLongArray(a); 
  
        // Displaying the AtomicLongArray 
        System.out.println("The array : " + arr); 
  
        // Index where operation is performed 
        int idx = 3; 
  
        // Value to expect at idx 
        long expect = 4; 
  
        // Value to update if current value 
        // is equal to expected value 
        long update = 40; 
  
        // Updating the value at idx 
        // applying compareAndSet 
        arr.compareAndSet(idx, expect, update); 
  
        // Displaying the AtomicLongArray 
        System.out.println("The array after update : "
                           + arr); 
    } 
}

输出：

The array : [1, 2, 3, 4, 5]
The array after update : [1, 2, 3, 40, 5]

示例2:

// Java program that demonstrates 
// the compareAndSet() function 
  
import java.util.concurrent.atomic.AtomicLongArray; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Initializing an array 
        long a[] = { 1, 2, 3, 4, 5 }; 
  
        // Initializing an AtomicLongArray with array a 
        AtomicLongArray arr = new AtomicLongArray(a); 
  
        // Displaying the AtomicLongArray 
        System.out.println("The array : " + arr); 
  
        // Index where operation is performed 
        int idx = 3; 
  
        // Value to expect at idx 
        long expect = 40; 
  
        // Value to update if current value 
        // is equal to expected value 
        long update = 4; 
  
        // Updating the value at 
        // idx applying compareAndSet 
        arr.compareAndSet(idx, expect, update); 
  
        // Displaying the AtomicLongArray 
        System.out.println("The array after update : "
                           + arr); 
    } 
}

输出：

The array : [1, 2, 3, 4, 5]
The array after update : [1, 2, 3, 4, 5]

参考：
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/AtomicLongArray.html#compareAndSet-int-long-long-

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注：本文由纯净天空筛选整理自rupesh_rao大神的英文原创作品 AtomicLongArray compareAndSet() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。