Here's my solution:
find /home/a/Desktop/myfolder -type d -exec sh -c '(cd {} && YOUR-COMMAND-GOES-HERE)' ';'
Instead of YOUR-COMMAND-GOES-HERE
you can put for example java -cp bin Main
So :
find /home/a/Desktop/myfolder -type d -exec sh -c '(cd {} && java -cp bin Main)' ';'