Java中的 AtomicReference compareAndSet() 方法及示例

AtomicReference类的compareAndSet()方法用于原子地将 value 设置为 newValue 到 AtomicReference 对象，如果 AtomicReference 对象的当前值等于 expectedValue 并且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，就好像变量被声明为易失性一样。

句法：

public final V compareAndSet(V expectedValue,
                             V newValue)

参数：此方法接受期望值和newValue ，这是要设置的新值。

返回值：该方法返回见证值，如果成功则与预期值相同。

下面的程序说明了 compareAndSet() 方法：
方案一：

// 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 ref
            = new AtomicReference();
  
        // 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

方案二：

// 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 ref
            = new AtomicReference();
  
        // 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

参考资料： https: Java/util/concurrent/atomic/AtomicReference.html#compareAndSet(V, V)