If you want midnight (0:00am) for the current date, you can just use the default constructor and zero out the time portions:
Date today = new Date();
today.setHours(0); today.setMinutes(0); today.setSeconds(0);
edit: update with Calendar
since those methods are deprecated
Calendar today = Calendar.getInstance();
today.clear(Calendar.HOUR); today.clear(Calendar.MINUTE); today.clear(Calendar.SECOND);
Date todayDate = today.getTime();