vysen wrote: -- bad advice --
That is untrue. They only require the Java RUNTIME ENVIRONMENT (JRE), not the Java DEVELOPMENT KIT (JDK). You only need the JDK if you want to compile the client yourself, and I don't see a reason to want to do so if you're not changing it.
I'm unsure about Mac, but on other operating systems it is a VERY bad idea to uninstall something by simply deleting its folder. It may be linked from various places (on Windows, notably, there are probably registry entries, but even on Linux some -- poorly written scripts -- may depend on the existence of a 'java' link on the search path). There should be some place to uninstall it, on linux e.g. by apt-get remove, on Windows from the software overview.
That said, there have been a lot of issues in the past with Mac and the mouse, and I never figured it out (mostly because I don't have a Mac available for testing).