Hi, I have done java programming for 4-5 years. I can do this project. Basically to improve performance you need a better implementation of data structures in java. For example you can use data structures like vectors or hashmaps etc. And you need some functionality implemented like tiidf implementation and counting the number of comparisons for stemming and removing stop words. Final function requires tiidf to be returned as a 2d array.
I can implement this for you, lets talk in chat for further discussion....