AtomicReferenceArray getAndAccumulate() method in Java with Examples

Last Updated : 03 Jan, 2020

The getAndAccumulate() method of a AtomicReferenceArray class is used to atomically updates the element at index i of AtomicReferenceArray with the results of applying the given accumulatorFunction to the current and given values and returns the previous value. The accumulatorFunction 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 E getAndAccumulate(int i, E x,
     BinaryOperator<E> accumulatorFunction)

Parameters: This method accepts:

i which is an index of AtomicReferenceArray to perform the operation accepts,
x which is the updated value and
accumulatorFunction which is a side-effect-free function of two arguments.

Return value: This method returns the previous value. Below programs illustrate the getAndAccumulate() method: Program 1:

Java

// Java program to demonstrate
// getAndAccumulate() method

import java.util.concurrent.atomic.*;
import java.util.function.BinaryOperator;

public class GFG {
    public static void main(String args[])
    {
        // an array
        Integer a[]
            = { 123, 1232, 1433, 134, 13415, 1343 };

        // AtomicReferenceArray with array
        AtomicReferenceArray<Integer> array
            = new AtomicReferenceArray<>(a);

        // Print AtomicReferenceArray
        System.out.println(
            "The AtomicReferenceArray before update: "
            + array);

        // Index and Value to apply getAndAccumulate
        int index = 2;
        int E = 3;

        // Declaring the accumulatorFunction
        // applying function
        BinaryOperator add
            = (u, v)
            -> Integer.parseInt(
                   u.toString())
                   * Integer
                         .parseInt(
                             v.toString());

        // apply getAndAccumulate()
        int value
            = array.getAndAccumulate(index, E, add);

        // print AtomicReferenceArray
        System.out.println(
            "previous value of index 2:"
            + value);
        System.out.println(
            "The AtomicReferenceArray after update: "
            + array);
    }
}

Output:

Program 2:

Java

// Java program to demonstrate
// getAndAccumulate() method

import java.util.concurrent.atomic.*;
import java.util.function.BinaryOperator;

public class GFG {
    public static void main(String args[])
    {
        // an array
        String a[] = { "GFG", "JS" };

        // AtomicReferenceArray with array
        AtomicReferenceArray<String> array
            = new AtomicReferenceArray<>(a);

        // Print AtomicReferenceArray
        System.out.println(
            "The AtomicReferenceArray before update : "
            + array);

        // Index and Value to apply getAndAccumulate
        int index = 1;
        String E = " PYTHON";

        // Declaring the accumulatorFunction
        // applying function to add value as string
        BinaryOperator add
            = (u, v) -> u.toString() + " and " + v.toString();

        // apply getAndAccumulate()
        String value
            = array.getAndAccumulate(index, E, add);

        // print AtomicReferenceArray
        System.out.println(
            "previous value of index 1:"
            + value);
        System.out.println(
            "The AtomicReferenceArray after update: "
            + array);
    }
}