How to inherit from an ancestor in Java? -

i have abstract base class , have concrete classes b , c extending , implementing abstract methods.

abstract class {...} class b extends {...} class c extends {...} 

now add functionality a, can not touch a, b , c. thought might possible write generic class d extending of concrete classes b or c.

class d<t> extends <t extends a> {...} 

is possible? , if correct syntax?