[java] No X11 DISPLAY variable was set, but this program performed an operation which requires it.
​goormIDE is an environment where there is no display.
So if you run it the same way as a normal Java program, an error will occur.
When creating Java projects, we provide templates such as
Java Swing, JavaFx, and Java AWT.
It includes example code and execution commands for GUI execution. You can test it!