Java - Design Pattern - Singleton

<source lang="Java">

public class SingletonClass {

   private static SingletonClass SINGLE_INSTANCE = null;

   private SingletonClass() {}

   public static SingletonClass getInstance() {
       if (SINGLE_INSTANCE == null) {
           synchronized (SingletonClass.class) {
               if (SINGLE_INSTANCE == null) {
                   SINGLE_INSTANCE = new SingletonClass();
               }
           }
       }
       return SINGLE_INSTANCE;
   }

} </source>