I am wondering if there is a way to check: for an abstract class, which classes extend the abstract class.
I am using IntelliJ IDEA.
For any class to show the type hierarchy (super- and/or subclasses), position the cursor on the class name and press Ctrl+H. This will show the tree of type hierarchy. You can toggle between showing sub-classes, super-classes and both.
Alternatively (thanks, @maydawn!) you can click the icon to the left of the line with the class name to show a popup with a list of sub-classes.