swing - nullpointerexception error in java gui -

i new cs student learning java. trying make gui user enter number , display result. getting errors not familiar with. have tried searching in google didnt help. comment appreciated. thanks.

main method person class

   import javax.swing.jframe;     public class person {         public static void main(string[] args) {             jframe frame= new guifirst();//line 6             frame.setdefaultcloseoperation(jframe.exit_on_close);             frame.setvisible(true);         }     } 

guifirst class

import javax.swing.jframe; import java.awt.event.actionlistener; import java.awt.event.actionevent; import javax.swing.jlabel; import javax.swing.jpanel; import javax.swing.jbutton; import javax.swing.jtextfield; public class guifirst extends jframe{     private jlabel label;     private jlabel label1;     private jtextfield text;     private jbutton button;     private jpanel panel;      public guifirst(){         label=new jlabel("enter number");         setsize(450,100);         text=new jtextfield(15);         button=new jbutton("calculate");          class addaction implements actionlistener{             public void actionperformed(actionevent event){                 double number=double.parsedouble(text.gettext());                 double result=number*number;                 label1=new jlabel("your result is"+result);             }         }          actionlistener listener=new addaction();         button.addactionlistener(listener);         panel=new jpanel();         panel.add(label);         panel.add(label1);//line 32         panel.add(text);         panel.add(button);         add(panel);     } } 

errors:

 exception in thread "main" java.lang.nullpointerexception         @ java.awt.container.addimpl(container.java:1090)         @ java.awt.container.add(container.java:410)         @ person.guifirst.<init>(guifirst.java:32)         @ person.person.main(person.java:6) 

you haven't initialized label1 line fails

panel.add(label1); 

you're trying initialize in method won't called until ui generated , button clicked

    class addaction implements actionlistener{         public void actionperformed(actionevent event){             double number=double.parsedouble(text.gettext());             double result=number*number;             label1=new jlabel("your result is"+result);         }     } 

this won't work because code won't executed until action performed. component (the label) needs non null before can added jpanel.

you need initialize default value start with.