So me and two friends are doing a project for our high school comp sci class. We’re using Swing to make GUIs, and hitting a few problems. We’ve hit a No X11 DISPLAY variable was set, but this program performed an operation which requires it. error, and I’ve never heard of an X11 DISPLAY, but following the error trail, it seems to be connected to a Headless Exception, about a missing display. I have a few vague ideas as to what it means, but it’s not helping much.