Java AtomicReference compareAndSet()用法及代码示例

如果AtomicReference对象的当前值等于期望值，则使用AtomicReference类的compareAndSet()方法以原子方式将newValue的值设置为AtomicReference对象，如果操作成功，则返回true，否则返回false。此方法使用设置的内存语义更新值，就像将该变量声明为volatile一样。

用法:

public final V compareAndSet(V expectedValue,V newValue)
参数：该方法接受ExpectedValue(期望值)和newValue(新值)来设置新值。
返回值：此方法返回见证值，如果成功，它将与期望值相同。

以下示例程序旨在说明compareAndSet()方法：
程序1:

// Java program to demonstrate
// AtomicReference.compareAndSet() method
import java.util.concurrent.atomic.AtomicReference;
public class GFG {
    public static void main(String[] args)
    {
        // create an atomic reference object. 
        AtomicReference<Long> ref = new AtomicReference<Long>(); 
        // set some value 
        ref.set(987654321L); 
        // apply compareAndSet() 
        boolean response 
            = ref.compareAndSet(1234L, 
                                999999L); 
        // print value 
        System.out.println(" Value is set = "
                           + response); 
    }
}

输出：

Value is set = false

程序2:

// Java program to demonstrate
// AtomicReference.compareAndSet() method
import java.util.concurrent.atomic.AtomicReference;
public class GFG {
    public static void main(String[] args)
    {
        // create an atomic reference object. 
        AtomicReference<String> ref 
            = new AtomicReference<String>(); 
        // set some value 
        ref.set("Geeks For Geeks"); 
        // apply compareAndSet() 
        boolean response 
            = ref.compareAndSet( 
            "Geeks For Geeks", 
            "GFG"); 
        // print value 
        System.out.println(" Value is set = "
                           + response); 
    }
}

输出：

Value is set = true