generics

[radhika ayirala]

interface Hungry<E> {void munch(E X); }

what is 'E' here.Is it a type of class.I read about "wild card notations",i understood them.I am not getting the meaning for say,

class abc<T>{
}

where do we use this kind of notation?

[Jesper de Jong]

See: Sun Java Language Guide - Generics.

The E and the T stand for types that are filled in later. For example in your class abc<T>, when you are going to use this class somewhere in your program, you must instantiate it by providing a real type, for example abc<String> obj = new abc<String>();

[Peter Mularien]

This generics paper from Sun (Gilad Bracha) is also a great introduction to the subject (although a bit academic in tone, so may be harder to read). It's linked at the bottom of the article that Jesper posted.

[Jesper de Jong]

Another very good website with everything you'll ever need to know about generics is Angelika Langer's Java Generics FAQ. It does go very deep into the details, probably deeper than what you need to know for the SCJP, however.