AtomicLongArray updateAndGet() method in Java with Examples

The Java.util.concurrent.atomic.AtomicLongArray.updateAndGet() is an inbuilt method in Java that updates the value at any given index of the AtomicLongArray after applying a given update function on the value at that index. The method takes the index value of the AtomicLongArray and the update function as the parameters and updates the value at that index by applying the update function on that value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads.

Syntax:

public final long updateAndGet(int i, LongUnaryOperator updateFunction)

Parameters: The function accepts two parameters:

i which is the index where update is to be made.

updateFunction which is the update function of single argument that tells what update is to be made.

Return value: The function returns a long value which is the value after applying the specified update function.

Below programs illustrate the above method:
Program 1:

// Java program that demonstrates
// the updateAndGet() 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 = 4;

        // Declaring the updateFunction
        LongUnaryOperator squaredFunction = (l) -> l * l;

        // Updating the value at idx
        // applying updateFunction
        arr.updateAndGet(idx, squaredFunction);

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

Output:

The array : [1, 2, 3, 4, 5]
The array after update : [1, 2, 3, 4, 25]

Program 2:

// Java program that demonstrates
// the updateAndGet() 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
        arr.updateAndGet(idx, cubeFunction);

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

Output:

The array : [1, 2, 3, 4, 5]
The array after update : [1, 2, 3, 64, 5]

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