One of the problems with developing in Java is that some relatively common tasks that ought to be simple require writing a lot of boilerplate code, or are otherwise inconvenient.
So, like many others before me, I have a bunch of classes that I use regularly. These are not clever, innovative, or terribly interesting. But they have saved me a lot of typing and repetition over the years.
I named them jingle and jumble. (There were jangle and jungle, which I think had something to do with networking and web services; I've lost those completely.)
The jingle classes help write swing applications. One of the most useful ones is a Frame registry that keeps track of how many windows you have open and allows you to close one or all of them.
In jumble, it's a case of allowing you to get a file into a string (or vice-versa) in one line.
They're used to simplify jkstat and solview.
(I don't really expect others to use them, though. I'm blogging just to note their existence.)