Java simple callback demo using Interface

CallbackDemo.java

public class CallbackDemo {

    public static void main(String[] args) throws InterruptedException {
        RestApiCall restApiCall = new RestApiCall();

        restApiCall.getUsersAsync(new UserListener() {
            @Override
            public void onDataReceived(String data) {
                System.out.println(data);
            }
        });

        restApiCall.getUsersSync(new UserListener() {
            @Override
            public void onDataReceived(String data) {
                System.out.println(data);
            }
        });
    }


    interface UserListener {
        public void onDataReceived(String data);
    }

    static class RestApiCall {

        public void getUsersSync(UserListener listner) throws InterruptedException {
            Thread.sleep(5000);
            listner.onDataReceived("alif here sync");
        }

        public void getUsersAsync(UserListener listener) {
            new Thread(() -> {
                try {
                    Thread.sleep(15000);
                    listener.onDataReceived("alif here async");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }

}