This is the most basic way to see if a command suceeded:
if jar cvfm control.jar Manifest <class list> ; then
echo "Success"
else
echo "Oops!"
fi
If you only want to detect failure, then invert the test:
if ! jar cvfm control.jar Manifest <class list> ; then
echo "Oops!"
fi
Or test the result explicitly:
jar cvfm control.jar Manifest <class list>
if (( $? )) ; then
echo "Oops!"
fi