refer link: http://www.javagyan.com/useful-tips/howtocreatethread-safesingleton A singleton class should be designed to ensures that there exists only one instance per application. Special care must be taken if your application is deployed on a clustered environment as in this case it is possible that multiple instance of your singleton class are available in your application. Here are a few ways to create a thread safe singleton classes in your application. 1) Lazy loading Singleton instance - Using Synchronized method or block public class SingletonClass{ private SingletonClass sc; private SingletonClass(){} public static SingletonClass getInstance(){ synchronized(SingletonClass.class) { if (sc == null) { sc = new SingletonClass(); } else { return sc; } } } } Issues - The use of synchronized keyword in a singleton class means that only one thread will be executing th