NoClassDefFoundError when developing a basic java SWING app -

i'm learning swing on intellij. made quick app on gui designer contains button. compiled fine whenever run it throws error

exception in thread "main" java.lang.noclassdeffounderror: com/intellij/uidesigner/core/gridlayoutmanager 

here's code (i run file main file)

import javax.swing.*; import java.awt.event.mouseadapter; import java.awt.event.mouseevent;  /**  * created leon_clemente on 6/3/15.  */ public class myfirsttest extends jframe {     private jtabbedpane tabbedpane1;     private jpanel panel1;     private jbutton browsebutton;     private jbutton uploadbutton;     private jcheckbox checkbox1;     private jcheckbox checkbox2;      public myfirsttest() { /*         browsebutton.addmouselistener(new mouseadapter() {             @override             public void mouseclicked(mouseevent e) {                 super.mouseclicked(e);             }         }); */         setvisible(true);     }      private void createuicomponents() {     } } 

so read on forums , thing relate problem running classpath not same compiling classpath(?) still don't idea though.

forms_rt.jar contains gridlayoutmanager class , jar located in (intellij idea root)\lib. search jar in compile environment.

add jar class path.

how set classpath - setting path of jar file