Performance issues comparing two vectors

Question

I need some advice on what is the fastest way to compare two vectors. My question is all about performance;
I have two vectors one(Vect A) of which has more than 20000 string values and the other Vector B would hold typically around 200 strings.I compare them both to find out if Vector B has values in Vector A and remove those.
I iterate thro each element in a loop from the smaller to the bigger vector comparing element by element.But it takes a long time.
Is there any quick way to do this comparison and can I use contains/compare methods instead of iterating thro the vectors.will it speeden up things
Arn

Answer 1

first of all, you should probably examine your collection choice and make sure that java.util.Vector is your best option (assumming you can change the class). Do not use a Hashtable as the previous poster suggested- it doesn't sound like you have a key/value type relationship in your elements, making a Map implementation superflous. Will there be duplicate elements in either Collection? If you will not have duplicate elements, you should probably use a Set collection instead of a List. Does your collection have to be thread-safe? If not, one of the unsynchronized collections should give you better performance (e.g. ArrayList should be quicker then Vector). For the best possible performance, you could use an ordered collection and write your own comparator, so that it does not iterate beyond what ever element assurres that there is no match (i.e. if the first element is "fred" in an ordered collection, you know there will be no match for "adam"). Sun has some good tutorials on the java.util.Collection package that will help you understand the benefit of each implemenation...
although, and I suppose this is neither here nor there, I wouldn't use java objects to sort through 20K string items- sounds like storing them in a database might be superior. Take care.