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The Java.util.concurrent.atomic.AtomicIntegerArray.accumulateAndGet() is an inbuilt method in java that atomically updates the element at index i with the results of applying the given function to the current and given values, returning the updated value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads. The function is applied with the current value at index i as its first argument, and the given update as the second argument. Syntax:

public final int accumulateAndGet(int i, int x, IntBinaryOperator accumulatorFunction)

Parameters: The function accepts three parameters:

i - The index where update is to be mada.

x - The value to make operation with value at i

accumulatorFunction - A side-effect-free function of two arguments.

Return value: The function returns the updated value which is in Integer. Below programs illustrate the above method: Program 1:

Java

// Java program that demonstrates
// the accumulateAndGet() function

import java.util.concurrent.atomic.AtomicIntegerArray;
import java.util.function.IntBinaryOperator;

public class GFG {
    public static void main(String args[])
    {
        // Initializing an array
        int a[] = { 1, 2, 3, 4, 5 };

        // Initializing an AtomicIntegerArray with array a
        AtomicIntegerArray arr = new AtomicIntegerArray(a);

        // Displaying the AtomicIntegerArray
        System.out.println("The array : " + arr);

        // Index where update is to be made
        int idx = 4;

        // Value to make operation with value at idx
        int x = 5;

        // Declaring the accumulatorFunction
        IntBinaryOperator add = (u, v) -> u + v;

        // Updating the value at idx
        // applying accumulatorFunction
        arr.accumulateAndGet(idx, x, add);

        // Displaying the AtomicIntegerArray
        System.out.println("The array after update : "
                           + arr);
    }
}

Output:

The array : [1, 2, 3, 4, 5]
The array after update : [1, 2, 3, 4, 10]

Program 2:

Java

// Java program that demonstrates
// the accumulateAndGet() function

import java.util.concurrent.atomic.AtomicIntegerArray;
import java.util.function.IntBinaryOperator;

public class GFG {
    public static void main(String args[])
    {
        // Initializing an array
        int a[] = { 17, 22, 33, 44, 55 };

        // Initializing an AtomicIntegerArray with array a
        AtomicIntegerArray arr = new AtomicIntegerArray(a);

        // Displaying the AtomicIntegerArray
        System.out.println("The array : " + arr);

        // Index where update is to be made
        int idx = 0;

        // Value to make operation with value at idx
        int x = 6;

        // Declaring the accumulatorFunction
        IntBinaryOperator sub = (u, v) -> u - v;

        // Updating the value at idx
        // applying accumulatorFunction
        arr.accumulateAndGet(idx, x, sub);

        // Displaying the AtomicIntegerArray
        System.out.println("The array after update : "
                           + arr);
    }
}

Output:

The array : [17, 22, 33, 44, 55]
The array after update : [11, 22, 33, 44, 55]

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/AtomicIntegerArray.html#getAndAccumulate-int-int-java.util.function.IntBinaryOperator-

AtomicIntegerArray accumulateAndGet() method in Java with Examples

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