<p>I'm working through some homework and a question on a previous exam paper asks to name all of the abstract classes in a given UML diagram. Fairly straightforward, I suppose. There are one abstract class and three interfaces. Do these interfaces qualify as abstract classes, in general?</p>

Yes, an Interface is implicitly Abstract. Look behind the scenes as to the way it is encoded to a
```
.class
```
file.
Semantics are a funny thing though; under exam conditions "abstract class" would have to literally be compiled from a
```
.java
```
source file using
```
abstract class
```
in the Class' declaration.