Instance Variable In Java

MainClass in Java Program

import javax.Swing.JFileChooser;
import javax.Swing.JFrame;
public class Mainclass extends JFrame
{
public MainClass()
{
JFileChooser filechooser=new JFileChooser();
filechooser.setDialogTitle("Choose a file");
this.getContentPane().add(fileChooser);
filechooser.setVisible(true);
}
public Static void main(String args[])
{
JFrame frame=new MainClass[])
{
JFrame frame=new MainClass();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}

}