Single Disign Pattern

If you want you System only have one Object .

On this Ocassion ,we can use the Single Pattern .

The main Format are as follows (in JAVA )

public class BS {  //Because our teacher use the BookSystem as an Example.

private static bs= new BS()

private BS(){

  //You can write code at this

}

public static BS getBS(){

   return bs;

   }

}

   I have see this Design pattern before,but today I answer the teacher'question,I said that the Factory Pattern can solve the problem that one class in the System that only Create one instance.I make a mistake.It's a very excellent Design Pattern.