Can a class inherit from both an Interface and a base class in Java?

Question

in .Net you can simply do this with the following code

Public class MyClass:ISomeInterface, SomeBaseClass

Can something similar be done in Java?

The code I have is as follows

public class InputHander extends OnTouchListener implements IControlHandler

However I get the error "no interface expected here" with regards to OnTouchListener

Yes of course. Have you gone through a basic Java tutorial, covering inheritance and interfaces? — Rohit Jain, Mar 13 '14 at 15:23
Classes don't inherit from interfaces, they just implement them. You can extend (inherit from) a single class, but you can implement multiple interfaces. — Anthony Grist, Mar 13 '14 at 15:24
So if an interface implements another interface does that use the extends keyword instead? — coolblue2000, Mar 13 '14 at 15:33
@coolblue2000 an interface cannot implement an interface. But it can extend other interfaces. — Puce, Mar 13 '14 at 15:34

Luiggi Mendoza · Accepted Answer · 2014-03-13T15:35:52.727

7

Yes, use the extends keyword for class inheritance and implements for interface implementation:

public class MyClass extends SomeBaseClass implements SomeInterface

From your question edit, you should use extends in class declaration for class inheritance. In other words, a class can only extend from another single class, not from interfaces. Multiple class inheritance is not allowed. In case you want to implement an interface, use implements keyword only. So, your code would be:

public class InputHander implements OnTouchListener, IControlHandler

More info:

Java Tutorials: Inheritance

edited Mar 13 '14 at 15:35

answered Mar 13 '14 at 15:23

Luiggi Mendoza

85,076
16
154
332

I get an error in Android Studio saying "No Interface expected here" with regards to the BaseClass. – coolblue2000 Mar 13 '14 at 15:26
@coolblue2000 it would be better if you edit your question and add your current code below the current content to get better help. – Luiggi Mendoza Mar 13 '14 at 15:27
Well, you actually can extend from interfaces, but only in other interfaces. – Puce Mar 13 '14 at 15:33
Ah, that makes sense now as I copied the call from an interface not a class.... Java is not entirely clear at times.... – coolblue2000 Mar 13 '14 at 15:35

score 3 · Answer 2 · answered Mar 13 '14 at 15:23

3

Yes. It takes couple of seconds to try it out:

public class MyClass extends MyAbstractClass implements MyInterface

answered Mar 13 '14 at 15:23

Konstantin Yovkov

62,134
8
100
147

score 2 · Answer 3 · edited May 23 '17 at 12:07

In order to prevent the pitfalls and complexities that arise if you have a language that supports multiple inheritance (e.g. C++), Java allows you to inherit from exactly one class (using extends and that class may or may not be abstract) and any number of interfaces (using implements).

So this is valid:

public class MyClass 
    extends SomeBaseClass 
    implements SomeInterface1, SomeInterface2

Java 8 will allow you to have default methods in interfaces but it's implemented carefully enough so as to avoid multiple inheritance ambiguities.

See Interface with default methods vs Abstract class in Java 8

Can a class inherit from both an Interface and a base class in Java?

3 Answers3