Java AtomicLongArray getAndAdd()方法及示例

Java.util.concurrent.atomic.AtomicLongArray.getAndAdd() 是Java中的一个内置方法，它可以在AtomicLongArray的索引处将给定的值原子化地添加到元素中。该方法将AtomicLongArray的索引值和要添加的值作为参数，并返回添加操作前的值。函数 getAndAdd() 与 addAndGet() 相似，但是前一个函数在添加操作之前返回值，而后一个函数在添加操作之后返回值。
语法

public final long getAndAdd(int i, long delta)

参数： 该函数接受两个参数。

• i – 要添加值的索引。
• delta – 要添加的值。

返回值： 该函数返回添加操作前的值，其单位为long。

以下程序说明了上述方法：

程序1 :

// Java program that demonstrates
// the getAndAdd() function
 
import java.util.concurrent.atomic.AtomicLongArray;
 
public class GFG {
    public static void main(String args[])
    {
        // Initializing an array
        long a[] = { 10, 22, 33, 44, 55 };
 
        // Initializing an AtomicLongArray with array a
        AtomicLongArray arr = new AtomicLongArray(a);
 
        // Displaying the AtomicLongArray
        System.out.println("The array : " + arr);
 
        // Index where value is to be added
        int idx = 0;
 
        // Value to add with value at idx
        long x = 16;
 
        // Updating the value at
        // idx applying getAndAdd and
        // storing the previous value
        long prev = arr.getAndAdd(idx, x);
 
        // Previous value at index idx
        // before update
        System.out.println("Value at index " + idx
                           + " before update is " + prev);
 
        // Displaying the AtomicLongArray
        System.out.println("The array after update : "
                           + arr);
    }
}

输出

The array : [10, 22, 33, 44, 55]
Value at index 0 before update is 10
The array after update : [26, 22, 33, 44, 55]

程序2：

// Java program that demonstrates
// the getAndAdd() function
 
import java.util.concurrent.atomic.AtomicLongArray;
 
public class GFG {
    public static void main(String args[])
    {
        // Initializing an array
        long a[] = { 1, 2, 3, 4, 5 };
 
        // Initializing an AtomicLongArray with array a
        AtomicLongArray arr = new AtomicLongArray(a);
 
        // Displaying the AtomicLongArray
        System.out.println("The array : " + arr);
 
        // Index where value is to be added
        int idx = 3;
 
        // Value to add with value at idx
        long x = 16;
 
        // Updating the value at
        // idx applying getAndAdd and
        // storing the previous value
        long prev = arr.getAndAdd(idx, x);
 
        // Previous value at index idx
        // before update
        System.out.println("Value at index " + idx
                           + " before update is "
                           + prev);
 
        // Displaying the AtomicLongArray
        System.out.println("The array after update : "
                           + arr);
    }
}

输出

The array : [1, 2, 3, 4, 5]
Value at index 3 before update is 4
The array after update : [1, 2, 3, 20, 5]

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