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I have a class, let's call it LineGraph, that renders a line graph. I need to subclass it, but the derived class is only used in one place and is coupled to the class that uses it. So I am using an inner class.
I see two ways to do this:
Anonymous inner class
public class Gui { LineGraph graph = new LineGraph() { // extra functionality here. }; } Named inner class
public class Gui { MyLineGraph graph = new MyLineGraph(); private class MyLineGraph extends LineGraph { // extra functionality here. } } I am not a fan of anonymous inner classes, because frankly I just think it looks really ugly. But in the case of a subclass that's only used in one place, is a named inner class overkill? What is the accepted practice?
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In simple words, a class that has no name is known as an anonymous inner class in Java. It should be used if you have to override a method of class or interface. Java Anonymous inner class can be created in two ways: Class (may be abstract or concrete).
A local inner class consists of a class declared within a method, whereas an anonymous class is declared when an instance is created. So the anonymous class is created on the fly or during program execution.
Lambda expression can be used where a class implements a functional interface to reduce the complexity of the code. An inner anonymous class is more powerful as we can use many methods as we want, whereas lambda expression can only be used where an interface has only a single abstract method.
An anonymous inner class can be useful when making an instance of an object with certain “extras” such as overriding methods of a class or interface, without having to actually subclass a class. Tip: Anonymous inner classes are useful in writing implementation classes for listener interfaces in graphics programming.
One advantage of anonymous inner classes is that no one can ever use it anywhere else, whereas a named inner class can be used (if only by the class that created it if made private). It's a small distinction, but it does mean that you can protect an inner class from being accidentally used elsewhere.
Also, using the anonymous inner class gives anyone reading your code a head's up - "this class is being used just here and nowhere else." If you see a named inner class, someone might think it'd be used in multiple places in the class.
They are very similar, so neither point is a game-changer. I just think it helps for clarity if you use anonymous inner classes for one-offs, and named inner classes when it's used multiple times within the class.
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