Inheriting JFrame violates Generalization

Question

While developing java stand alone applications , some developers tend to extend JFrame class and Implement(realize) some actionlistener interface . Does it not violate The generalization concept in oops and also abstraction . Does it not violate Single responsibility principle too.

[EDIT] By violate The generalization concept in oops , i mean "is-a" relationship becomes void. Inherit a class changed to extend a class

What according to you is the generalization concept and abstraction? You may be right abut the single responsibility principle violation but I need to see the code to confirm this. — Chetan Kinger, Jul 18 '15 at 11:26
I'm not ready with the code yet. But abstraction means making the object do things and contains things ,that is relevant to the object. And to give a UI to any executor program which we do by inheriting JFrame we violate generalization. Is 'nt it? — Abdul Rahman K, Jul 18 '15 at 11:32

score 3 · Accepted Answer · edited May 23 '17 at 12:14

This frequently seen anti-pattern poses several problems:

class Application extends JFrame implements ActionListener {}

Given a preference for composition over inheritance, an Application might have a JFrame, but it should only extend JFrame to override its existing functionality.
Implementing an interface in this way can lead to leaking this in a constructor. This compounds the problem of ensuring that Swing GUI objects are constructed and manipulated only on the event dispatch thread.
Regarding generalization, a JFrame is a specialization of Window, used as a top-level container. Don't confuse the containment hierarchy with the class hierarchy.
Regarding single responsibility, the JFrame API shows a coherent derivation, despite Swing's history and cross-platform abstraction.

Implementing a control interface, such as ActionListener, may be convenient for a self-contained example, but a complex application will likely need more than one controller. An example using jmapviewer is examined here. See also Why CS teachers should stop teaching Java applets.

I didnt confuse with containment hierarchy, but was curious if IS-A relationship being violated as a result? — Abdul Rahman K, Jul 18 '15 at 13:19
Sorry if I seemed [sententious](https://www.google.com/search?q=sententious) about potential confusion. Based on the [API](https://docs.oracle.com/javase/8/docs/api/javax/swing/JFrame.html) and [history](http://stackoverflow.com/q/2004759/230513), I would say that the `JFrame` derivation is reasonably coherent. Do you see a specific anomaly? — trashgod, Jul 18 '15 at 19:34
It will accept the answer if you can brief about vioaltion of single responsibility principle — Abdul Rahman K, Jul 19 '15 at 02:27

janos · Answer 2 · 2015-07-18T12:37:30.250

Your question is a bit confusing and hard to understand, because you're using strange terminology. These sentences are correct and mean something:

a class extends another class
a class implements an interface
a class inherits methods from its parent class

These sentences are inappropriate, unclear:

a class inherits another class
violate generalization concept

Especially without code, I can only guess what you're asking, but I try to answer anyway:

a class that extends JFrame and at the same time implements an action listener interface, violates the single responsibility principle by being 2 things at once
a class that extends JFrame and at the same time contains some logic not related to displaying or configuring a JFrame, violates the single responsibility principle by doing 2 things at the same time. It also violates good separation of model-view-controller
a class that extends JFrame, but in terms of its behavior / implementation it's not mainly a JFrame but something else, then it violates the abstraction of a JFrame, and it shouldn't extend JFrame but possibly contain it instead

So what about Abstraction and is-a relationship ? Will only MVC seperation be violated? Thanks for the response. And for correction — Abdul Rahman K, Jul 18 '15 at 12:24
You're right, yes, good abstraction will be violated too. I added one more point in my answer — janos, Jul 18 '15 at 12:38

Inheriting JFrame violates Generalization

2 Answers2