Shaaf, Syed's blog

A technical blog about Java, Kubernetes and things that matter

Command, Singleton, JMenuItem, JButton, AbstractButton - One Listener for the app

Here I would like to demonstrate a simple use of JMenuItems being used with Single Listener for the entire system. A simple sample of use would probably be SingleInstance Desktop Application. Lets see how that is done here. First lets create a OneListener class that should be able to listen to ActionEvents and also be able to add Commands to itself. Please refer to my previous post on Command,Singleton if you would like to see more about this patterns and there usage.


By using the command pattern you are seperating the operation from the invoking object. And just because of that it becomes easier to change the command without chagning the caller/s. This means that you could use Command pattern when you might have the following situation You want to parameterize objects to perform an action You want to specify, execute and queue requests at different times. Just to quickly start you need a command object, An interface will keep it easy going in this case, thus providing you with the option of extending other classes e.

Implementing the adapter

Typically when implementing an interface you would have to implement all the methods that exist in that interface. A very good example is the MouseListener in the java Swing. When you need to implement more then one method where as typically you might be catching only one of them. Saying that you would also find a Mouse Adapter provided as well. Some of us use that often. And that is part of the Adapter pattern.

Quick start Singleton - Walk through

This being my first existence on the network and I just want to make sure that I would come back to this blog page again sometime and keep on writing. For now this is a quick 5 min walk through of getting your hands dirty on the Singleton Pattern. As any ones first pattern Singleton always seems to be the easiest to adapt and ironically always the mistress of your pains; when you realize the act wasn’t right in the first place.