Singleton Example

ThreadSafeSingleton.java

package singleton;

public class ThreadSafeSingleton {

	//1.private Constructor
		private ThreadSafeSingleton() {
			
		}
		//2.Only Instance of the Class
	    private static  ThreadSafeSingleton instance = new ThreadSafeSingleton();

	    //3.Public method to enable global access
	    public static synchronized ThreadSafeSingleton getClassInstance() {
	    	if(instance == null){
	    		instance = new ThreadSafeSingleton();
	        }
	        return instance;
	    }
	    
	  // to avoid overhead by synchronized 
	    public static ThreadSafeSingleton getInstanceUsingDoubleLocking(){
	        if(instance == null){
	            synchronized (ThreadSafeSingleton.class) {
	                if(instance == null){
	                    instance = new ThreadSafeSingleton();
	                }
	            }
	        }
	        return instance;
	    }
}