design pattern Singleton

1. public class SimpleSingleton {
2. private SimpleSingleton singleInstance = null;
4. //Marking default constructor private
5. //to avoid direct instantiation.
6. private SimpleSingleton() {
7. }
9. //Get instance for class SimpleSingleton
10. public static SimpleSingleton getInstance() {
12. if(null == singleInstance) {
13. singleInstance = new SimpleSingleton();
14. }
16. return singleInstance;
17. }
18. }
    

in multi-thread environment, please use:

public static synchronized SimpleSingleton getInstance() { }