I received the following results of
sudo apt-get install gcj in Ubuntu 16.04.
$ sudo apt-get install gcj Reading package lists... Done Building dependency tree Reading state information... Done Package gcj is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'gcj' has no installation candidate
How to install gcj on Ubuntu 16.04?
gcjis deprecated and removed from the GCC trunk. You should consider changing the compiler. Check the Wikipedia page: en.wikipedia.org/wiki/GNU_Compiler_for_Java