Java 中的 AtomicLongArray getAndUpdate()方法，示例
原文:https://www . geeksforgeeks . org/atomicongarray-getandupdate-method-in-Java-with-examples/
Java . util . concurrent . atomic . AtomicLongArray . Getandupdate()是 Java 中的一个内置方法，它在对 atomicongarray 的任何给定索引处的值应用给定的更新函数后，更新该索引处的值。该方法将原子克隆数组的索引值和更新函数作为参数，并通过对该值应用更新函数来更新该索引处的值。该函数应该没有副作用，因为当尝试的更新由于线程之间的争用而失败时，它可能会被重新应用。 getAndUpdate() 和 updateAndGet() 函数唯一的区别是前者返回更新前的值，后者返回更新后的值。
语法:
公共最终长 getAndUpdate(int i，longunaryooperator updateFunction)
参数:该函数接受两个参数:
-
i 是要进行更新的索引。 updateFunction* which is the update function of single argument that tells what update is to be made.
返回值:函数返回一个长值，即应用指定的更新函数后的值。
以下程序说明了上述方法: 程序 1:
```java // Java program that demonstrates // the getAndUpdate() function
import java.util.concurrent.atomic.AtomicLongArray; import java.util.function.LongUnaryOperator;
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 = 3;
// Declaring the updateFunction LongUnaryOperator squaredFunction = (l) -> l * l;
// Updating the value at idx // applying updateFunction and // storing the previous value long prev = arr.getAndUpdate(idx, squaredFunction);
// Displaying the previous value System.out.println("The value before update" + " at index " + idx + " is " + prev);
// Displaying the AtomicLongArray System.out.println("The array after update : " + arr); } } ```
Output:
```java The array : [1, 2, 3, 4, 5] The value before update at index 3 is 4 The array after update : [1, 2, 3, 16, 5]
```
程序 2:
```java // Java program that demonstrates // the getAndUpdate() function
import java.util.concurrent.atomic.AtomicLongArray; import java.util.function.LongUnaryOperator;
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 = 3;
// Declaring the updateFunction LongUnaryOperator cubeFunction = (l) -> l * l * l;
// Updating the value at idx // applying updateFunction and // storing the previous value long prev = arr.getAndUpdate(idx, cubeFunction);
// Displaying the previous value System.out.println("The value before update" + " at index " + idx + " is " + prev);
// Displaying the AtomicLongArray System.out.println("The array after update : " + arr); } } ```
Output:
```java The array : [1, 2, 3, 4, 5] The value before update at index 3 is 4 The array after update : [1, 2, 3, 64, 5]
```
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