Exception in thread "main" java.awt.HeadlessException: No X11 DISPLAY variable was set, but this program performed an operation which requires it. at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:159) at java.awt.Window.(Window.java:432) at java.awt.Frame.(Frame.java:403) at javax.swing.JFrame.(JFrame.java:202) at DrawGUI.(DrawGUI.java:15) at ShapeCreator.(ShapeCreator.java:31) at ShapeCreator.main(ShapeCreator.java:138)
Что означает это сообщение об ошибке? И как я могу его решить?