Sorting a HashMap by date

Question

In a Java class I have a method to reOrder an existing HashMap by date. The HashMap is of a type where the Object contains a field called exp

Answer 1

If you just need the minimum or maximum date, a simple for each loop might be sufficient:

Date maxDate = null;
for (Entry item: hashMap.entrySet()) 
    if (maxDate == null || maxDate before((Date)item.getValue())) 
        maxDate = (Date)item.getValue();

This way complexity is only O(n) and insert and delete operations are cheaper than using a sortedMap. Anyway, I think patstuart's suggestion (using a sortedMap) is more elegant.