Error when using apt on macOS Sierra
apt, the package manager, is a Linux tool, from Debian GNU/Linux. macOS does not have it.
There are projects like Homebrew, MacPorts and Fink that provides packaged third-party software for macOS.
- Homebrew: https://brew.sh/
- MacPorts: https://www.macports.org/
- Fink: http://www.finkproject.org/
NetBSD's pkgsrc also works nicely on macOS: http://www.pkgsrc.org/
As for md5sum: On the BSD Unices, of which macOS is one, there is often a utility called md5 available that performs the same service (but with slightly different format of output).
If you install GNU coreutils using the tools provided by one of the above projects, md5sum will be installed. The executable is sometimes called gmd5sum (note the added g prefix, which also gets added to all other GNU coreutils executables).
macOS doesn’t use the APT package management tools, at least not by default. Here you’re ending up trying to run Java’s annotation processing tool.
If you want to check out package management tools on macOS, see How to install apt-get or YUM on Mac OS X; Fink allows you to install apt-get.