All ImageJ results tables can be saved either in ‘Comma Separated Value’ (.csv) or whitespace/tabstop separated format (generated when saving with a .xls extension, but actually just a plain text ...

If you want to learn how to use ImageJ and/or ImageJ2 (as opposed to write programs with ImageJ2), then visit ImageJ Tutorials. This project contains example code for working with ImageJ2 and SciJava.