Error in calling Super() method cannot reference ...

Question

import javax.swing.JFrame;
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class MyFrame extends JFrame {
String St="Rayudu";
     JPanel jp1= new JPanel();
     JButton jb1=new JButton("Hello");     
public MyFrame() {
super("Document :" + St);
          jp1.add(jb1);
          getContentPane().add(jp1);
//...Then set the window size or call pack...
setSize(300,300);
//Set the window's location.
     setLocation(300,300);
     setVisible(true);
public static void main(String ar[])
MyFrame mf=new MyFrame();
mf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
C:\java>javac My*.java
MyFrame.java:11: cannot reference St before supertype constructor has been called
super("Document :" + St);
^
1 error
Can anyone explain?
thanks in advance.

Answer 1

Change your constructor to take an argument of type String, pass this along to the super method when you call the new instance of your class in main. ie:
public myFrame( String title ) {
super( "Document: " + title );
st = title; //if you need it in that String Object assign it here.
//etc...
public static void main( String args[] ) {
new myFrame( "Testing" );
Does this answer your question?