Say your client is super happy with your application - but they've realized that birds don't only fly() and flapWings() besides the stuff other animals do. Story: man purchases plantation on planet, finds 'unstoppable' infestation, uses science, electrolyses water for oxygen, 1970s-1980s. I realize I could do the following: For various reasons I need an interface that has both methods. I got error doing this. Connect and share knowledge within a single location that is structured and easy to search. Is there a way to achieve something similar while avoiding the empty interface (using generics or otherwise)? Best Testing Courses | Do weekend days count as part of a vacation? Inheriting multiple interfaces isn't problematic, since you're simply defining new method signatures to be implemented. I thought multiple inheritance was always illegal in Java, but this code compiles: Would having an empty interface such as AB be considered a bad practice? BoxAdcontent.document.write("