Callback method example in Java

Here I am showing a simple example on what is callback method in Java. A callback is a piece of code that you can pass as an argument to be executed on some other code. Since Java doesn’t yet support function pointer, the callback methods are implemented as command objects.

A callback will usually hold reference to some state to which it actually becomes useful.

By making the callback implementation in your code, you gain indirection between your code and the code that is executing the callback.

So, a callback method can be any method in any class; a reference to an instance of the class is maintained in some other class, and, when an event happens in other class, it calls the method from the first class.

The only thing that makes it a callback as distinguished from any other method call is the idea of handling a reference to an object for the purpose of having that object invokes a method on it later, usually on some events.

Let’s say you are calling a method from another method, but the key is that the callback is treated like an Object, so you can change which method to call based on the state of the system (like the Strategy Design Pattern).

Callback Method Example

My own Callable interface.


interface Callable {

	void call();


Worker class who calls the callback.


public class Worker {

	public void doWork(Callable callable) {
		System.out.println("Doing Work");;


public class CallBackMethodApp {

	public static void main(String[] args) {

		new Worker().doWork(new Callable() {
			public void call() {
				System.out.println("Callback Called");



Executing the above main class will give you the following output:

Doing Work
Callback Called

Hope you got an idea how to write callback method in Java programming language.

Source Code


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