http://jreepad.sourceforge.net/

Jreepad is an open-source re-working of Treepad Lite in Java.

Jreepad is not affiliated with Treepad - it's an independent project.

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It also has some wiki capabilities.
From the user manual:

Jreepad adapts some of the ideas from wiki. The key ingredient in a wiki is that if you type a WikiWord, which is any word which begins with a capital letter and has other capital letter(s) somewhere in the middle, the wiki converts this into a link to an article of that name. If the article exists, you can jump straight to it. If the article doesn't exist, it gets created and you can start to type text into it.

You can also force a chunk of text to behave like a WikiWord by wrapping it in [[double square brackets]].

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CategoryWikiImplementation