What is the point of inner classes?

We use inner classes to logically group classes and interfaces in one place to be more readable and maintainable . Additionally, it can access all the members of the outer class, including private data members and methods.

Use a non-static nested class (or inner class) if you require access to an enclosing instance’s non-public fields and methods . Use a static nested class if you don’t require this access.

They’re not “bad” as such . They can be subject to abuse (inner classes of inner classes, for example). As soon as my inner class spans more than a few lines, I prefer to extract it into its own class. It aids readability, and testing in some instances.