Note that a
java.util.Date object represents a specific point in time. It does not represent a duration, and you can't really use
java.util.Date objects to store durations. In fact, the standard
Java API does not have anything to store time durations at all. Despite what Ulf says, you can't use
SimpleDateFormat really well for working with durations.
To work with durations, you can use a third-party library such as the popular open source
Joda Time library. You can use the
org.joda.time.format.PeriodFormatter class of that library to parse and format strings that represent durations.