SingletonClass.java

public class SingletonClass {

    private static volatile SingletonClass sSoleInstance;

    //private constructor.
    private SingletonClass(){

        //Prevent form the reflection api.
        if (sSoleInstance != null){
            throw new RuntimeException("Use getInstance() method to get the single instance of this class.");
        }
    }

    public static SingletonClass getInstance() {
        //Double check locking pattern
        if (sSoleInstance == null) { //Check for the first time
          
            synchronized (SingletonClass.class) {   //Check for the second time.
              //if there is no instance available... create new one
              if (sSoleInstance == null) sSoleInstance = new SingletonClass();
            }
        }

        return sSoleInstance;
    }
}