How do I make a method accept instances with two interfaces? [duplicate]

Question

I have a couple of interfaces:

public interface Speaker {     void speak(); }  public inteface Walker {     void walk(); } 

I want a method that takes instances that are both a Speaker and a Walker.

Now, I could implement another interface:

public interface WalkerSpeaker extends Walker, Speaker {  } 

And accept that:

void walkAndTalk(final WalkerSpeaker x) {     x.walk();     x.speak(); } 

But this is quite cumbersome with many combinations, and every implementation must inherit from WalkerSpeaker for it to work!

Is there a better way?

Answer 1

You can achieve this with generics as follows

public <T extends Speaker & Walker> void walkAndTalk(T x) {     x.walk();     x.speak(); } 

The type parameter T will be "double-bounded" to both interfaces, so in essence T will be a WalkerSpeaker except you don't have to write a separate interface for it.