Java, searching within a list of objects?

Question

I'm a bit lost on the way to make this happen the fastest. I have a large list of objects that have basic variable attributes (with getters / setters) and I need to do a search in this list to find the objects within the list that match a given parameter

I have found how to do a regular list search but I need to, for example search for the value of the result of doing a call getName() for each object in the list and get objects that have a result that matches my input.

Something like below where the third argument is the result of the method call and the second is what I am trying to find.

   int index = Collections.binarySearch(myList, "value", getName());

Any advice is appreciated

Answer 1

If you just as a one-off operation need to find the object(s) whose getName() is a particular value, then there's probably not much magic possible: cycle through the list, call getName() on each object, and for those that match, add them to your list of results.

If getName() is an expensive operation and there's some other way of a-priori working out if a given object definitely won't return a matching value, then obviously you can build in this 'filtering' as you cycle through.

If you frequently need to fetch objects for a given getName(), then keep an index (e.g. in a HashMap) of [result of getName()->object -> list of matches]. You'll need to decide how and if you need to keep this "index" in synch with the actual list.

See also the other proposition to use binarySearch() but to keep the list maintained. This way, inserts are more expensive than with a map and unsorted list, but if inserts are infrequent compared to lookups, then it has the advantage of only needing to maintain one structure.