I am sure I would be able to find the answer if I knew the right terminology for some of these things, but basically the problem is:
Every time I have run a something in Eclipse (Java) before, there has been a square red button (hovertext "Terminate") in the "Console" tab of the bottom-right (wide) window (in "Java" perspective) that I could use to terminate a program.
I recently added a new project (to isolate and figure out some code I was having trouble with in the main project...but that's a different story), and now: (a) it seems to be running more than just what I want it to run, and (b) the red button is sometimes not available, but clearly something is running because when I hover over the "Run", button, it says "Run [program name here] (already running)" instead of "Run [program name here]".
Can anyone tell me why this would happen? Can anyone tell me how to terminate a program when you don't have a terminate button?
(...and I won't ask here how to get Eclipse to stop running things I don't want it to run, since I haven't scoured the internet for the answer to that one for long enough to justify a StackOverflow question, but it's probably coming...)
Update: This button cleared things up (after the double-x icon button hint helped). Eclipse should really have a separate "Console" tab for each console, though!
Sometimes the running console can be hidden behind a terminated console. Look for the grey double-x on the console display to remove inactive consoles, and see if your red box shows up again.