Java AtomicLongArray getAndSet()方法及示例

Java.util.concurrent.atomic.AtomicLongArray.getAndSet() 是Java中的一个内置方法，它可以在AtomicLongArray的任何给定位置原子化地设置一个给定值。该方法接受AtomicLongArray的索引值和要设置的值作为参数。在设置该索引的新值之前，它返回给定索引的值。函数 getAndSet() 与 set() 函数类似，但前者返回值，而后者不返回任何值。
语法

public final long getAndSet(int i, long newValue)

参数： 该函数接受两个参数。

• i – 要进行更新的索引。
• newValue – 要在索引i处设置的值

返回值： 该函数返回更新前给定索引的值，其单位为long。

下面的程序说明了上述方法。

程序1 :

// Java program that demonstrates
// the getAndSet() function
  
import java.util.concurrent.atomic.AtomicLongArray;
  
public class GFG {
    public static void main(String args[])
    {
        // Initializing an array
        long a[] = { 11, 12, 13, 14, 15 };
  
        // 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 = 0;
  
        // New value to set at idx
        long val = 100;
  
        // Updating the value at
        // idx applying getAndSet
        // and store previous value
        long prev = arr.getAndSet(idx, val);
  
        // Previous value at idx before update
        System.out.println("Value at index " + idx
                           + " before the update is "
                           + prev);
  
        // Displaying the AtomicLongArray
        System.out.println("The array after update : "
                           + arr);
    }
}

输出。

The array : [11, 12, 13, 14, 15]
Value at index 0 before the update is 11
The array after update : [100, 12, 13, 14, 15]

程序2

// Java program that demonstrates
// the getAndSet() function
  
import java.util.concurrent.atomic.AtomicLongArray;
  
public class GFG {
    public static void main(String args[])
    {
        // Initializing an array
        long a[] = { 11, 12, 13, 14, 15 };
  
        // 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;
  
        // New value to set at idx
        long val = 10;
  
        // Updating the value at
        // idx applying getAndSet
        // and store previous value
        long prev = arr.getAndSet(idx, val);
  
        // Previous value at idx before update
        System.out.println("Value at index " + idx
                           + " before the update is "
                           + prev);
  
        // Displaying the AtomicLongArray
        System.out.println("The array after update : "
                           + arr);
    }
}

输出。

The array : [11, 12, 13, 14, 15]
Value at index 3 before the update is 14
The array after update : [11, 12, 13, 10, 15]

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