variables

 

  Local variables which are declared (1) inside code blocks or (2) inside methods get no default initialization. 

You must initialize them or get an  error. 

 

  Member variables (class or instance variables) do get initialized automatically.

 

 Object reference variables get a null initialization.

 

  You cannot put these on variables:  abstract, native, or synchronized.

 

  Variables can be interface types.  i.e.

 

Runnable  r ;       works