Hello, so I have this JFrame, and on one computer it worked fine, but when I transferred my project over to another computer it started to have issues, sometimes it would work like a charm without a hitch, and others setPreferredSize() doesn't work, so it creates a JFrame that is the minimum size and them crashes because of things that depend on window size.

Thanks,
h3ckboy

"sometimes it works" is a key phrase for threading issues, maybe improper dealing with threads.

The contents (component/jpanel/wat), are they changing in run?

What works for me is calling setSize and setPreferredSize both with same value.

What about adding a JPanel to the JFrame, calling setPreferredSize() on the panel, and pack() on the frame.  Then add your components to the panel.  It's normally the panel you want a particular size anyway, not the window.