Hi, Guys.
I'm calculating the correlation coefficient between two HashMaps of Stock Prices keyed on Dates. However, the Dates do not always line up perfectly. So, I need to line-up the two HashMaps by their Keys.

Thus far, I'm creating two ArrayLists of the Dates, doing retainAll between them and then copying over the HashMaps using only the matching Dates.
This probably less than ideal.
If someone has a more efficient way, please let me know.
Help me out, Daniweb.

Maybe just loop through the keys of one of the Maps, deleting all the entries that don't have a corresponding key in the second Map?