Phoenix is a modern open-source Code Editor for the web
Apache NetBeans
A free C, C++ and Fortran IDE
AstroNvim is an aesthetic and feature-rich neovim config
A web based file manager, web IDE / browser based code editor
Kotlin code completion, diagnostics and more for any editor/IDE
Learn Java the easy way!
A powerful editor and graphical debugger for code written in Scilab
Web IDE in single HTML file
A syntax highlighting, code folding text component written in Swing
IDLE Extensions
Launch an external diff tool like WinMerge in Eclipse
Open-source plugins included in the distribution of IntelliJ IDEA
Vim-like editing in Eclipse
Literate programming for eclipse
a DSL for type systems, reduction rules, interpreters for Xtext langs
Develop AMX NetLinx projects in the Sublime Text editor.