SingleTon

public class SingleTon {

private static SingleTon singleTon = null;

private SingleTon() {

System.out.println("instance...");

}

public static SingleTon getInstance() {

if (singleTon == null) {

singleTon = new SingleTon();

return singleTon;

}

return singleTon;

}

public void sum() {

System.out.println("services");

}

}