Java AtomicLongArray getAndUpdate()用法及代碼示例

Java.util.concurrent.atomic.AtomicLongArray.getAndUpdate()是Java中的一種內置方法，該方法將給定索引值上的給定更新函數後，對該AtomicLongArray任意索引處的值進行更新。該方法將AtomicLongArray的索引值和update函數作為參數，並通過對該值應用update函數來更新該索引處的值。該函數應無副作用，因為當嘗試更新由於線程間爭用而失敗時，可能會重新應用該函數。 getAndUpdate()和updateAndGet()函數之間的唯一區別是，前者返回更新前的值，而後者返回更新後的值。

用法:

public final long getAndUpdate(int i, LongUnaryOperator updateFunction)

參數：該函數接受兩個參數：

i這是要進行更新的索引。
updateFunction這是單個參數的更新函數，用於指示要進行的更新。

返回值：該函數返回一個long值，該值是應用指定的update函數後的值。

以下示例程序旨在說明上述方法：
示例1:

// 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); 
    } 
}

輸出：

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]

示例2:

// 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); 
    } 
}

輸出：

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]

參考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/AtomicLongArray.html#getAndUpdate-int-java.util.function.LongUnaryOperator-

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注：本文由純淨天空篩選整理自rupesh_rao大神的英文原創作品 AtomicLongArray getAndUpdate() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。