JStudio is a free integrated development environment (IDE) for developing Java console programs or Android apps on your Android device. The app comes with several features, including code completion, real-time error checking, and auto-backup. JStudio's editor is equipped with an auto-completion feature that suggests options for code as you type. It also has a real-time error checking feature that highlights errors as you type, enabling you to fix them immediately.

JStudio's editor also comes with an undo and redo feature that allows you to undo or redo any changes you make. The app also supports characters not typically present in the virtual keyboard, such as tabs and arrows. The terminal feature in JStudio allows you to access the shell and commands that ship with Android, and it comes preinstalled with basic Unix commands like grep and find.  

Lastly, the app comes with a file manager that allows you to access your files without leaving the app. You can copy, paste, and delete files using the file manager.