This is a Super Simple Java Editor written entirely in Java. It allows you to compile and run java programs in an mdi interface with syntax highlighting and easy commenting. Currently in suspended development. Available as a jar and an msi.
EditPlus is a text editor, HTML editor, PHP editor and Java editor for Windows. While it can serve as a good Notepad replacement, it also offers many powerful features for Web page authors and programmers.
HTML / CSS / JS / PHP/ ASP/ PERL / JAVA editor with syntax highlighting, split screen editing and other essential tools. Tag Explorer - an HTML and user resources storage. Ability to create and reuse code fragments.
DJ Java Decompiler is Windows 95/98/Me/NT/2K/XP/2003/Vista decompiler and disassembler for Java that reconstructs the original source code from the compiled binary CLASS files (for example Java applets).
FavoText is a text editor based on 'Scintilla' component, which supports editing file with text/hex format, syntax highlighting and auto completion; it also offers many powerful features for Web page authors and programmers.
If you like PC games then you should know Irrlicht Engine, a multiplatform graphics engine (it works as much for Windows as for Linux and MacOS) totally written in C++, which produces 3D images, something needed in high quality games.