java - Code fault of falseException in thread -

i "falseexception" while running following code:

import java.awt.eventqueue;  import javax.swing.jframe; import javax.swing.jpanel; import java.awt.borderlayout; import java.awt.event.actionevent; import java.awt.event.actionlistener;  import javax.swing.jlabel; import javax.swing.jtextfield; import javax.swing.jbutton; import javax.swing.swingconstants;   public class deneme implements actionlistener {      private jframe frmasaltesti;     private jtextfield yazi;     sayi s1 =new sayi();     string sondurum="";     jlabel sonuc;        /**      * launch application.      */     public static void main(string[] args) {         eventqueue.invokelater(new runnable() {             public void run() {                 try {                     deneme window = new deneme();                     window.frmasaltesti.setvisible(true);                 } catch (exception e) {                     e.printstacktrace();                 }             }         });     }      /**      * create application.      */     public deneme() {         initialize();     }      /**      * initialize contents of frame.      */     private void initialize() {         frmasaltesti = new jframe();         frmasaltesti.settitle("asal testi");         frmasaltesti.setresizable(false);         frmasaltesti.setbounds(100, 100, 307, 167);         frmasaltesti.setdefaultcloseoperation(jframe.exit_on_close);          jpanel panel = new jpanel();         frmasaltesti.getcontentpane().add(panel, borderlayout.center);          jlabel lbldenemekistediinizsayy = new jlabel("denemek istedi\u011finiz say\u0131y\u0131 girin!");         panel.add(lbldenemekistediinizsayy);          yazi = new jtextfield();         yazi.settext("0");         panel.add(yazi);         yazi.setcolumns(4);          jbutton button = new jbutton("test et");         panel.add(button);          jlabel sonuc = new jlabel("sonuç");         panel.add(sonuc);         button.addactionlistener(this);        }      @override     public void actionperformed(actionevent e) {         int gelen=0;         gelen=integer.parseint(yazi.gettext());         system.out.println(s1.asalmi(gelen));         if(s1.asalmi(gelen))         {             sondurum="girilen sayı asaldır";         }         else         {             sondurum="girilen sayı asal değildir";         }              sonuc.settext(""+sondurum);      }    } 

the error, linked line: sonuc.settext(""+sondurum);, is:

     falseexception in thread "awt-eventqueue-0"  java.lang.nullpointerexception     @ deneme.actionperformed(deneme.java:94) 

i couldn't find solution , waiting answers. want change label dynamic label.

you nullpointerexception @ line

sonuc.settext(""+sondurum); 

what possibly null @ line , cause such exception? answer: sonuc.

so, sonuc initialized somewhere?

the place sonuc referenced in code in initialize() method:

jlabel sonuc = new jlabel("sonuç"); 

and creates local variable same name field sonuc. field sonuc never initialized.

replace above line by

this.sonuc = new jlabel("sonuç");