AWT-Shutdown and AWT-EventQueue do not terminate after plotting a 2D graph with JFreeChart

I am trying to do something really basic; Plot an array of integers as time-series data using JFreeChart. Previously the code was working perfectly fine. That is the point that drives me crazy. However, now it fails to terminate after doing everything it is supposed to do. Active threads are as follows;

Thread[AWT-Shutdown,5,main]
Thread[AWT-EventQueue-0,6,main]
Thread[main,5,main]

I am using a Macbook wit开发者_如何学运维h Mac OS 10.6.8 on it, and got a set of recent software updates.

Does anybody have any clue about where to start, and what to look for?

You can get more infomation from the terminal:

1. Launch your program in the background

   $ java -jar dist/program.jar &
   

2. Get its process id

   $ ps
     PID TTY           TIME CMD
     714 ttys000    0:00.01 -bash
     727 ttys000    0:01.52 /usr/bin/java -jar dist/program.jar
   

3. Obtain a thread dump

   $ kill -QUIT 727
   

4. Look for anything not in State: WAITING or State: RUNNABLE

Your IDE's profiler may offer a more friendly view of the same information. See also JLS §12.8 Program Exit. An sscce may help, too.