java - Private variable cannot reference to another method in the same class -

im new java , today have problem code when trying actionlistener java class here:

public class exam{     private void createform(){         ...         jbutton jbtn = new jbutton("ok");         jbtn.addactionlistener((actionlistener) this);         ...     }     public static void main(string[] args){         exam ex = new exam();         ex.createform();     }     public void actionperformed(actionevent ae){         //ide show no variable name "jbtn"         if (ae.getsource() == jbtn){             ...         }     } }    

your jbtn variable declared within createform method. java uses called "scoping rules" make sure don't accidentally use variables don't mean to. declaring jbtn in createform, telling java compiler want use in method, , else. called "local" variable (as in, local method).

you want use "member variable" (it member of class). declared inside class, outside of method. in case, looks this:

public class exam{     jbutton jbtn;      private void createform(){         ...         jbtn = new jbutton("ok");         jbtn.addactionlistener((actionlistener) this);         ...     } 

the declaration of variable @ class level, , in createform being referenced in same way in actionperformed.

this basic concept in java, might want take @ java tutorials go on ground. official tutorial place start.