What is jqsiestartdetectorimpl class as an add on?

It appears to be the Java Quickstater browser plugin. As mentioned before, it shows up in a lot of hijack this entries, but not as a threat (lots of people have this as it is installed in the latest versions of java). If you are concerned, feel free to disable it or remove it. The only downside is you may have to wait an extra second or two for a web java application to start up (ex: chat rooms).