JD-GUI is a standalone graphical utility that displays Java source codes of “.class” files. You can browse the reconstructed source code with the JD-gui for instant access to methods and fields. This project may be freely used for personal needs in a commercial or non-commercial environments. It is not included or embedded into commercial software products, but may be used in the free use of JD-Guizmo for personal purposes.Download: http://www.jfizmo.com/JD-gui-guizmo-gui.
Source: https://thehackernews.com/2011/08/jd-gui-fast-java-decompiler-download.html