When you're looking at your source and wondering "how the hell did I get here? Am I on the Swing worker thread, or...", there's a few things you can do to make finding the answer easier.
You've already looked at the call hierarchy with Ctrl+Alt+H, and you can't figure it out. One approach is to just slap down a breakpoint and restart under the Eclipse debugger, but if you put the breakpoint in a method that's called commonly, and you're instead looking for the uncommon hit, it's going to be really annoying to have the debugger jump up every three seconds and click "nope, nope, next, etc" while looking at the call stack.
So here's the second option: good old printf debugging. Now there's no one-liner (that I know of) in Java to just dump the current stack (You could instantiate a Throwable and tell it to print its stack in like 2 lines, but how ugly is that?), so here's a little utility class (ThreadUtil.java) you can grab: