Java AtomicLong compareAndSet()用法及代码示例

Java.util.concurrent.atomic.AtomicLong.compareAndSet()是Java中的一种内置方法，如果当前值等于参数给定的期望值，则将值设置为参数中的传递值。该函数返回一个布尔值，该布尔值使我们了解更新是否完成。

用法:

public final boolean compareAndSet(long expect,
                                       long val)

参数：该函数接受两个强制性参数，如下所述：

expect:指定原子对象应为的值。
val:如果原子整数等于期望值，则指定要更新的值。

返回值：该函数返回一个布尔值，成功则返回true，否则返回false。

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.AtomicLong; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
  
        // Initially value as 0 
        AtomicLong val = new AtomicLong(0); 
  
        // Prints the updated value 
        System.out.println("Previous value: "
                           + val); 
  
        // Checks if previous value was 0 
        // and then updates it 
        boolean res = val.compareAndSet(0, 6); 
  
        // Checks if the value was updated. 
        if (res) 
            System.out.println("The value was "
                               + "updated and it is "
                               + val); 
        else
            System.out.println("The value was "
                               + "not updated"); 
    } 
}

输出：

Previous value: 0
The value was updated and it is 6

示例2:

// Java program that demonstrates 
// the compareAndSet() function 
  
import java.util.concurrent.atomic.AtomicLong; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
  
        // Initially value as 0 
        AtomicLong val = new AtomicLong(0); 
  
        // Prints the updated value 
        System.out.println("Previous value: "
                           + val); 
  
        // Checks if previous value was 0 
        // and then updates it 
        boolean res = val.compareAndSet(10, 6); 
  
        // Checks if the value was updated. 
        if (res) 
            System.out.println("The value was "
                               + "updated and it is "
                               + val); 
        else
            System.out.println("The value was "
                               + "not updated"); 
    } 
}

输出：

Previous value: 0
The value was not updated

参考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/AtomicLong.html#compareAndSet–

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注：本文由纯净天空筛选整理自gopaldave大神的英文原创作品 AtomicLong 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。