Generics Default Constructor Java

Question

public class Sample<T>{

 T data;

   Sample(){

     data = ????;

  }

}

How can i assign a default value to data ?

Duplicate of : http://stackoverflow.com/questions/182636/how-to-determine-the-class-of-a-generic-type — Nicolas, Oct 18 '10 at 08:35

johncip · Answer 1 · 2010-10-18T08:33:40.820

8

Bozho is right (you can't). If you definitely want it to start off with a value, make that value an argument to the constructor. For instance:

public class Sample<T> {
  T data;
  Sample(T data) {
     this.data = data;
  }
}

edited Oct 18 '10 at 08:33

answered Oct 18 '10 at 07:33

johncip

score 7 · Answer 2 · answered Oct 18 '10 at 07:29

7

You can't. The type T is erased at runtime, so you can't instantiate it.

If you pass a Class argument to the Sample(..) constructor, you can call clazz.newInstance()

answered Oct 18 '10 at 07:29

Bozho

7

*"You can't."* ... unless the default value is `null`. :-) – Stephen C Oct 18 '10 at 07:35

2 Answers2