Recursively add files by pattern

You can use git add [path]/\*.java to add java files from subdirectories,
e.g. git add ./\*.java for current directory.

From git add documentation:

Adds content from all *.txt files under Documentation directory and its subdirectories:

$ git add Documentation/\*.txt

Note that the asterisk * is quoted from the shell in this example; this lets the command include the files from subdirectories of Documentation/ directory.