Java中的 AtomicLongArray getAndAdd() 方法及示例

Java.util.concurrent.atomic.AtomicLongArray.getAndAdd()是Java中的一个内置方法，它以原子方式将给定值添加到 AtomicLongArray 索引处的元素。该方法以 AtomicLongArray 的索引值和要添加的值作为参数，返回添加操作前的值。 getAndAdd()函数与addAndGet () 函数类似，但前者函数返回添加操作之前的值，而后者返回添加操作之后的值。
句法：

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：函数返回加法运算前的值，在long中。
下面的程序说明了上述方法：
方案一：

Java

// 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]

方案二：

Java

// 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：
https://docs.oracle.com/javase/8/docs/api/java Java