Hello, I would like to use a pop up or joption pane to show an alert when a validator executes. I’ve tried on fields and on message validator but I always get this exception:
Caused by: java.awt.HeadlessException
at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:159)
at java.awt.Window.(Window.java:432)
at java.awt.Frame.(Frame.java:403)
at java.awt.Frame.(Frame.java:368)
Can anybody help me?
Thanks in advance