Java AtomicLongArray getAndIncrement()方法及示例

Java.util.concurrent.atomic.AtomicLongArray.getAndIncrement() 是Java中的一个内置方法，它可以将AtomicLongArray的任何索引上的值原子化地增加1。该方法以AtomicLongArray的索引值为参数，返回递增前该索引的值，然后递增该索引的值。函数 getAndIncrement() 与 incrementAndGet() 函数类似，但前者返回增量前的值，而后者返回增量操作后的值。

语法

public final long getAndIncrement(int i)

参数： 该函数接受一个参数i，它是进行增量操作的索引。

返回值： 该函数返回更新前该索引的先前值，该值为long。

下面的程序说明了上述方法。

程序1 :

// Java program that demonstrates
// the getAndIncrement() 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;
  
        // Updating the value at
        // idx applying getAndIncrement
        // and storing the previous value
        long prev = arr.getAndIncrement(idx);
  
        // 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 : [12, 12, 13, 14, 15]

程序2

// Java program that demonstrates
// the getAndIncrement() 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;
  
        // Updating the value at
        // idx applying getAndIncrement
        // and storing the previous value
        long prev = arr.getAndIncrement(idx);
  
        // 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, 15, 15]

注意： 函数getAndIncrement()与incrementAndGet()相似，但后者的函数返回更新的值，而前者则返回更新后的先前值。

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