Question

Basically I want to do this:

public interface A {     void a(); } public interface B {     void b(); } public class SomeClass {     public SomeClass(<A&B> e) { // Note the type here         e.a();         e.b();     } } 

What I did on the commented line is obviously illegal. I know I can just require the passed object to implement interface A, or interface B, but is there a way to do both?

I guess there are workarounds (like requiring the parameter to be of type A and then check if it is also an instanceof B), but that way I don’t get help from the compiler. Do you know of any way to do this? Or maybe a smarter workaround…

Answer 1

You can do it with generics enabled. For example, to accept an instance of some class that implements both CharSequence and Appendable:

  public <T extends CharSequence & Appendable> void someMethod(T param) {     ...   }