So, how do you know if your applications require JAVA? Of course, first, I'd download the latest JRE to your HDD just in case stuff stops working.
If you had the documentation for all of your software items, the system requirements section might specify JAVA version xx. For example, Symantec/Norton products usually use JAVA as a basis. Not every product does; some are based on other development systems such as Microsoft . As for using an older version: Many people are still using Windows XP and Oracle has capped versions that will run under XP because, well, they don't want to test under XP.
(Eventually, one of our users: the FBI, demanded the application be rewritten, and it was.
To summarize: if you don't update JAVA and don't update your apps, then you might be O. for your system not dying (of course, you might be leaving yourself open for a vulnerability or two).
It will install the latest version if it's not installed, or will upgrade to the latest.
You can also use it to uninstall the programs and audit the computers for the software packages it covers.
EXE using the processor, that could be a sign you need JAVA.
There also were/are computers that were UNIX systems (Solaris, HP_UX, etc.).
There is usually a warning if you try to install a newer version of JAVA on XP that this may or may not work too well (just so they warn you).
We had an application at work that was written a long time ago and they found it only ran on JAVA 1.6. So the programmer advised new users of the system that they had to uninstall the latest and go back to the older JAVA.
If I choose not to update it, will it leave my system crippled somewhere or possibly vulnerable to anything? Since you seem not to know a lot about what JAVA is, I'll try to just cover the basics.
Can I live without it and is it possible to remove it altogether? I am too lazy to look up dates but I'm sure that you can if that is important. You have the "Windows" computers that are derivatives of the old IBM PC line of computers.