Can an abstract class have multiple interface classes in Java?

To add to the other replies, there is something in regards to implementing multiple interfaces you should look out for.

When you implement interfaces that share methods with the same or an ambiguous signature, it's no longer possible to predict to which interface the method belongs. This can become a serious problem if at least one of these interfaces provide a defaultimplementation.

You can try this yourself:

1. Without default implementation:

  • Create two interfaces that contain a method with identical signatures (name and parameter list) and return types.
  • Create a (non-abstract) class that implements these interfaces.

2. One with default implementation:

  • Repeat the steps from the first example.
  • Provide a default implementation for one of the interfaces.

3. Both with default implementation:

  • Repeat the steps from the first example.
  • Provide a default implementation for both of the interfaces.
/r/javahelp Thread