Date today = new Date();
Date tomorrow = new Date(today.getTime() + (1000 * 60 * 60 * 24));
Date has a constructor using the milliseconds since the UNIX-epoch. the getTime()-method gives you that value. So adding the milliseconds for a day, does the trick. If you want to do such manipulations regularly I recommend to define constants for the values.
Important hint: That is not correct in all cases. Read the WARNING comment, below.
