Java command line "shell" with auto-complete

Check out JReadline and jline2.

Update: picocli-shell-jline2 and picocli-shell-jline3 combine the strength of JLine 2 and 3 with picocli.

Picocli allows you to write commands (and subcommands) with options and positional parameters using very little code, and the library will generate JLine 2 and 3 command completers for all commands.

It uses ANSI colors and styles in the usage help message, and has many other unique features like negatable options, repeatable nested argument groups, variable interpolation and more.

Disclaimer: I am the author and therefore biased.