AtomicReference compareAndExchange() method in Java with Examples

The compareAndExchange() 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.This method will return the witness value, which will be the same as the expected value. This method handles the operation with memory semantics of reading as if the variable was declared volatile.

Syntax:

public final V compareAndExchange(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 compareAndExchange() method:
Program 1:



filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to demonstrate
// AtomicReference.compareAndExchange() 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<Integer> ref
            = new AtomicReference<Integer>();
  
        // set some value
        ref.set(999);
  
        // apply compareAndExchange()
        Integer oldValue
            = ref.compareAndExchange(
                999,
                999999);
  
        // print value
        System.out.println("Witness Value= "
                           + oldValue);
    }
}

chevron_right


Output:

Program 2:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to demonstrate
// AtomicReference.compareAndExchange() 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("GFG");
  
        // apply compareAndExchange()
        String oldValue
            = ref.compareAndExchange(
                "GFG",
                "Geeks for Geeks");
  
        // print value
        System.out.println("Witness Value= "
                           + oldValue);
    }
}

chevron_right


Output:

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

Don’t stop now and take your learning to the next level. Learn all the important concepts of Data Structures and Algorithms with the help of the most trusted course: DSA Self Paced. Become industry ready at a student-friendly price.




My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.