Java Collections - Effienct search for DateTime ranges

I have a case where I have a table (t1) which contains items like

 | id | timestamp | att1 | att2 |

Now I have to iterate over a collection of elements of type att1 and get all records from t1 which are between two certain timestamps for this att1. I have to do this operation several times for a single att1.

So in order to go easy on the database queries, I intended to load every entry from t1 which has a certain att1 attribute once into a collection and perform the subsequent searches on this collection.

Is there a collection that could handle a search like between '2011-0开发者_StackOverflow中文版2-06 09:00:00' and '2011-02-06 09:00:30'? It's not guaranteed to contain entries for those two timestamps.

Before writing an implementation for that (most likely a very slow implementation ^^) I wanted to ask you guys if there might be some existing collections already or how I could tackle this problem.

Thanks!

Yes. Use TreeMap which is basically a sorted map of key=>value pairs and its method TreeMap::subMap(fromKey, toKey).

In your case you would use timestamps as keys to the map and for values att1 attribute or id or whatever else would be most convenient for you.

The closest I can think of, and this isn't really what I would consider ideal, is to write a comparator that will sort dates so that those within the range count as less than those outside the range (always return -1 when comparing in to out, 0 when comparing in to in or out to out, and always return +1 when comparing out to in.

Then, use this comparator to sort a collection (I suggest an ArrayList). The values within the range will appear first.

You might just be better off writing your own filter, though. Input a collection (I recommend a LinkedList), iterate over it, and remove anything not in the range. Keep a master copy around for spawning new ones to pass into the filter, if you need to.

You can make the object you want in your collection, which I think is att1, implement the Comparable interface and then have the compareTo method compare the timestamp field. With this in place it will work in any sorted collection, such as a treeSet, making it easy to iterate and pull out everything in a certain range.