What is Singletone class?

Question

I would desire to apprehend the brief description about usage of Singletone class and where it can be applied.plz help me

Answer 1

example
public class Singleton {
private static Singleton INSTANCE = null;
// Private constructor suppresses
// default public constructor
private Singleton() {}
//synchronized creator to defend against
multi-threading issues
//another if check here to avoid multiple
instantiation
private synchronized static void createInstance()
if (INSTANCE == null) {
INSTANCE = new Singleton();
public static Singleton getInstance() {
if (INSTANCE == null) createInstance();
return INSTANCE;
Thanks
Siju Kurian
Starmark service ltdDon't use this example in real applications, it has a serious flaw. Read http://java.sun.com/developer/technicalArticles/Programming/singletons/ .This example is implementation of Double-checked locking, which lacks proper synchronization.
In almost all cases, solution provided by georgemc is applicable - it is simple and provides lazy initialization unless class have other non-private static methods/fields or non-private constructors (which may trigger initialization of class when used) (JLS, 12.4.1).