Some interesting pointers about Java: post 1 & also post 2 by verdyp which are both very entailed. lol
Java is not very memory efficient unfortunately.

You can reduce drag on your system by using a few small tips: Don't resume all your files. Set your downloads to auto-clear. Close/hide windows you're not using at that time (eg: connections, monitor & library windows.) Reduce the no. of shared folders or files or choose smaller files as alternatives. Reduce the no. of incomplete files by going to to incomplete folder (whilst LW is closed) & deleting those at 0 KB. Then open LW & arrange your downlds by Progress (click on top of progress column bar) & delete all those at 0%. Delete search results that are older than a few hours (they go stale after a while anyway.) Other things you might consider are reduce either or both upload & download bandwidth. Disable ultrapeer capabilities under Speed in options.

Allow LW to settle down before doing anthing with LW. Give it 20 or 30 mins before using it. Just some ideas.