AtomicReference compareAndExchangeRelease() method in Java with Examples

The compareAndExchangeRelease() method of a AtomicReference class is used to Atomically sets the value to newValue to AtomicReference object, if the current value of AtomicReference object which is referred to as the witness value is equal to the expectedValue and returns the witness value. This method updates the value and ensures that prior loads and stores are not reordered after this access.

Syntax:

public final V compareAndExchangeRelease(
                                  V expectedValue,
                                  V newValue)

Parameters: This method accepts expectedValue which is the expected value and newValue which is the new value to set.

Return value: This method returns the witness value, which will be the same as the expected value if successful.

Below programs illustrate the compareAndExchangeRelease() method:
Program 1:

// Java program to demonstrate
// AtomicReference.compareAndExchangeRelease() method

import java.util.concurrent.atomic.AtomicReference;

public class GFG {
    public static void main(String[] args)
    {

        // create an atomic reference object
        // which stores Integer.
        AtomicReference<Long> ref
            = new AtomicReference<Long>();

        // set some value
        ref.set(987654321L);

        // apply compareAndExchangeRelease()
        long oldValue
            = ref.compareAndExchangeRelease(
                987654321L,
                999999L);

        // print value
        System.out.println("Witness Value = "
                           + oldValue);
    }
}

Output:

Program 2:

// Java program to demonstrate
// AtomicReference.compareAndExchangeRelease() method

import java.util.concurrent.atomic.AtomicReference;

public class GFG {
    public static void main(String[] args)
    {

        // create an atomic reference object.
        AtomicReference<String> ref
            = new AtomicReference<String>();

        // set some value
        ref.set("Geeks For Geeks");

        // apply compareAndExchangeRelease()
        String oldValue
            = ref.compareAndExchangeRelease(
                "Geeks For Geeks",
                "GFG");

        // print value
        System.out.println("Witness Value = "
                           + oldValue);
    }
}

Output:

References: https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/atomic/AtomicReference.html#compareAndExchangeRelease(V, V)