java pattern for time intervall calculation

I am searching for a java pattern. Can you please suggest a pattern for following feature: I have a table with two type of timestamps. (columns: TIME, TYPE) One timestamp type represents a begin of an intervall and the other type an end of an intervall. I need to transform this table into another table (colums: BEGINTIME, ENDTIME). After the transformation the second table should store closed and not overlapping intervals. I have to consider different uses cases, e.g. when one timestamp is after 24:00 then take 24:00 instead of 1:00.

I search for a java pattern where I can add new use cases without change old use cases. Can you please suggest a java pattern?

Thx. Br, Stenly