Java中的 AtomicReferenceArray compareAndSet() 方法及示例

AtomicReferenceArray类的compareAndSet()方法用于原子地将 AtomicReferenceArray 的索引 i 的值设置为 newValue，如果 AtomicReferenceArray 对象的索引 i 处的当前值等于 expectedValue。如果更新成功，此方法将返回 true。

句法：

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

参数：此方法接受：

• i是执行操作的 AtomicReferenceArray 的索引，
• expectedValue是期望值和
• newValue是要设置的新值。

返回值：该方法成功返回true ，返回false表示实际值不等于预期值。

下面的程序说明了 compareAndSet() 方法：

方案一：

// Java program to demonstrate
// compareAndSet() method
  
import java.util.concurrent.atomic.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // create an atomic reference object.
        AtomicReferenceArray ref
            = new AtomicReferenceArray(3);
  
        // set some value
        ref.set(0, 1234);
        ref.set(1, 4322);
  
        // apply compareAndSet()
        boolean op1
            = ref.compareAndSet(0, 5434, 8913);
        boolean op2
            = ref.compareAndSet(1, 3236, 6543);
  
        // print
        System.out.println("Operation at index 0: "
                           + op1);
        System.out.println("Operation at index 0: "
                           + op2);
    }
}

输出：

Operation at index 0: false
Operation at index 0: false

方案二：

// Java program to demonstrate
// compareAndSet() method
  
import java.util.concurrent.atomic.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // create an atomic reference object.
        AtomicReferenceArray ref
            = new AtomicReferenceArray(3);
  
        // set some value
        ref.set(0, "GFG");
        ref.set(1, "JS");
  
        // apply compareAndSet()
        boolean op1
            = ref.compareAndSet(
                0, "GFG",
                "GEEKS FOR GEEKS");
        boolean op2
            = ref.compareAndSet(
                1, "JS",
                "JAVA SCRIPT");
  
        // print
        System.out.println("Operation at index 0: "
                           + op1);
        System.out.println("New value at index 0: "
                           + ref.get(0));
        System.out.println("Operation at index 1: "
                           + op2);
        System.out.println("New value at index 1: "
                           + ref.get(1));
    }
}

输出：

Operation at index 0: true
New value at index 0: GEEKS FOR GEEKS
Operation at index 1: true
New value at index 1: JAVA SCRIPT

参考： https: Java/util/concurrent/atomic/AtomicReferenceArray.html#compareAndSet(int, E, E)