Java 中的 AtomicLongArray getAndAccumulate()方法，示例
原文:https://www . geeksforgeeks . org/atomicongarray-getandaccumulate-method-in-Java-with-examples/
Java . util . concurrent . atomic . AtomicLongArray . getandaccumulate()是 Java 中的一个内置方法，它在将给定函数应用于当前值和给定值后，用结果自动更新 atomicongarray 的任何索引处的值，返回前一个值。此方法接受要执行操作的原子克隆数组的索引、执行操作的值和累加器函数作为参数。应用该函数时，索引处的当前值作为其第一个参数，给定的更新作为第二个参数。累加器函数应该没有副作用，因为当由于线程之间的争用导致尝试的更新失败时，它可以被重新应用。函数 getAndAccumulate() 与accumulated gt()类似，但前者在更新前返回值，后者在更新后返回值。
语法:
公共最终长 getAndAccumulate(int i，long x，LongBinaryOperator 累加器函数)
参数:该函数接受三个参数:
-
I–要进行更新的索引。 x–用 I 处的值进行运算的值 accumulatorFunction – A side-effect-free function of two arguments.
返回值:该函数返回更新前的值，该值在长中。 以下程序说明上述方法: 程序 1:
```java // Java program that demonstrates // the getAndAccumulate() function
import java.util.concurrent.atomic.AtomicLongArray; import java.util.function.LongBinaryOperator;
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 update is to be made int idx = 4;
// Value to make operation with value at idx long x = 5;
// Declaring the accumulatorFunction LongBinaryOperator add = (u, v) -> u + v;
// Updating the value at idx // applying getAndAccumulate long prev = arr.getAndAccumulate(idx, x, add);
// The previous value at idx System.out.println("Value at index " + idx + " before update is " + prev);
// Displaying the AtomicLongArray System.out.println("The array after update : " + arr); } } ```
Output:
```java The array : [1, 2, 3, 4, 5] Value at index 4 before update is 5 The array after update : [1, 2, 3, 4, 10]
```
程序 2:
```java // Java program that demonstrates // the getAndAccumulate() function
import java.util.concurrent.atomic.AtomicLongArray; import java.util.function.LongBinaryOperator;
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 update is to be made int idx = 0;
// Value to make operation with value at idx long x = 6;
// Declaring the accumulatorFunction LongBinaryOperator sub = (u, v) -> u - v;
// Updating the value at idx // applying getAndAccumulate long prev = arr.getAndAccumulate(idx, x, sub);
// The previous value at idx System.out.println("Value at index " + idx + " before update is " + prev);
// Displaying the AtomicLongArray System.out.println("The array after update : " + arr); } } ```
Output:
```java The array : [1, 2, 3, 4, 5] Value at index 0 before update is 1 The array after update : [-5, 2, 3, 4, 5]
```
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