In order to use gcj to compile the java binding, you must also have development

files of libgcj.  On Debian systems that translates to:

 - gcj 3.3 -> libgcj4-dev

 - gcj 3.4 -> libgcj5-dev

 - gcj 4.0 -> libgcj6-dev

 - gcj 4.1 -> libgcj7-dev

 - gcj 4.2 -> libgcj8-dev

 - gcj 4.3 -> libgcj9-dev