To amplify, the problem is not Java, that is just the language (and runtime) that some program was created in. The problem (it seems) is that some program is running, and you would not like it to. You have to figure out what the program is, and then decide whether you want to disable it.
Better than even money this is some program that you enabled yourself, that runs a background process, and that is running heavily. My first though is that some bittorrent clients are written in Java (but that is just a random thought).