JMathLib is a clone of Matlab and Octave but written 100% in java.
License: Freeware
OS Support: Linux, Linux Open Source, WinXP, WinNT 4.x, WinNT 3.x, WinME, Win Vista, Win98, Win95, Linux Gnome, Unix, Java

Converts text with many possible cleanups and transformations.
License: Freeware
OS Support: Linux, Mac OS X, WinXP, WinNT 4.x, WinME, Win Vista, Win98, Linux Gnome, OS/2, OS/2 Warp, OS/2 Warp 4, Java

XMLFox is a validating XML editor, available as a desktop application.
License: Freeware
OS Support: WinXP, WinNT 4.x

Displays a variety of decorative borders Shows off what you can do with Swing.
License: Freeware
OS Support: Linux, Linux Console, Mac OS X, WinXP, WinNT 4.x, WinNT 3.x, WinME, Win Vista, Win98, Linux Gnome, Unix, OS/2, OS/2 Warp, OS/2 Warp 4, Java, AS/400

Used to accumulate values by category.
License: Freeware
OS Support: Linux, Linux Console, Mac OS X, WinXP, WinNT 4.x, WinNT 3.x, WinME, Win Vista, Win98, Linux Gnome, Unix, OS/2, OS/2 Warp, OS/2 Warp 4, Java, AS/400

Freeware NET Obfuscator Skater Light Edition is free .
License: Freeware
OS Support: WinXP, WinNT 4.x

How to Interconvert any of the Java primitives Conversion Amanuensis.
License: Freeware
OS Support: Linux, Mac OS X, WinXP, WinNT 4.x, WinME, Win Vista, Win98, Linux Gnome, OS/2, OS/2 Warp, OS/2 Warp 4, Java

A Rapid Application Development framework for light weight database applications.
License: Freeware
OS Support: Linux, WinXP, Win Vista, Java

common utility classes that work under Java 11+.
License: Freeware
OS Support: Linux, Linux Console, Mac OS X, WinXP, WinNT 4.x, WinNT 3.x, WinME, Win Vista, Win98, Linux Gnome, Unix, OS/2, OS/2 Warp, OS/2 Warp 4, Java, AS/400

Seccia is a software development environment that offers you powerful assistance with your object-oriented programming.
License: Freeware
OS Support: WinXP, Win Vista