Java experts.Please answer this question

Hi

class A {
int i, j;
}
class B {
int i, j;
}
class C extends A {
int k;
}
class D extends A {
int k;
}
public class ins {
public static void main(String args[]) {
A a = new A();
B b = new B();
C c = new C();
D d = new D();
if(a instanceof A)
System.out.println("a is instance of A");
if(b instanceof B)
System.out.println("b is instance of B");
if(c instanceof C)
System.out.println("c is instance of C");
if(c instanceof A)
System.out.println("c can be cast to A");
if(a instanceof C)
System.out.println("a can be cast to C");
System.out.println();
// compare types of derived types
A object;
object = d; // A reference to d
System.out.println("object now refers to d");
if(object instanceof D)
System.out.println("object is instance of D");
System.out.println();
object = c; // A reference to c
System.out.println("object now refers to c");
if(object instanceof D)
System.out.println("object can be cast to D");
else
System.out.println("object cannot be cast to D");
if(object instanceof A)
System.out.println("object can be cast to A");
System.out.println();

}
}

------------------------------------------

Read for more information.

http://www.roseindia.net/java/beginners/nonstaticvariable.shtml

package UI;

import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Paint;
import java.awt.PaintContext;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.Rectangle2D;
import java.awt.image.ColorModel;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JInternalFrame;
import javax.swing.JLabel;
import javax.swing.JRootPane;

public class MainUI extends JDialog implements MouseListener {


    /**
     * @param args
     */

    static String[][] templocations=new String[5][];
    static int check1,check2,check3,check4,check5;
    ImageIcon imgicon;
    Image img;
    static JButton butt;
    JLabel addlabel,configure,exit;
    static Container con;
    EnlargeUI largeUI;
    static int count=0;
    static File savelocations = new File("e:\\Dock\\ObjectDock.doc");
    static File savealwaysonTop = new File("e:\\Dock\\alwaysonTop.doc");
    AddFrame temp=new AddFrame(this);
    static String checkTop="";

    public MainUI(){
        con = getContentPane();

        try{
            CreateButton button=new CreateButton("","",this);
            setUndecorated(true);
            setBounds(0, 0, 500, 65);
            setLayout(null);

            try {
                if(!savelocations.exists()){
                    savelocations.createNewFile();
                    // TODO Auto-generated catch block
                }
                if(!savealwaysonTop.exists()){
                    savealwaysonTop.createNewFile();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

            try {
                Scanner scanFile=new Scanner(savelocations);
                while(scanFile.hasNext()){
                    String[] splitLocations=scanFile.nextLine().split(";");
                    AddFrame.GetID.setText(splitLocations[0]);
                    templocations[Integer.parseInt(splitLocations[0])-1]=new String[2];
                    templocations[Integer.parseInt(splitLocations[0])-1][0]=splitLocations[1];
                    templocations[Integer.parseInt(splitLocations[0])-1][1]=splitLocations[2];
                    AddFrame.GetPath.setText(splitLocations[1]);
                    AddFrame.GetTarget.setText(splitLocations[2]);
                    System.out.println(splitLocations[0]);

                    AddFrame.addShortCuts();
                }
                scanFile.close();
                Scanner scanFile1=new Scanner(savealwaysonTop);
                while(scanFile1.hasNext()){
                    checkTop=scanFile1.nextLine();
                }
                if(checkTop.equalsIgnoreCase("True")){
                    ConfigureUI.alwaysonTop.setSelected(true);
                }else{
                    ConfigureUI.alwaysonTop.setSelected(false);
                }
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            addlabel = new JLabel("ADD");
            addlabel.setBounds(400, 5, 50, 25);
            addlabel.addMouseListener(this);

            configure = new JLabel("CONFIGURE");
            configure.setBounds(400, 20, 70, 25);
            configure.addMouseListener(this);

            exit = new JLabel("EXIT");
            exit.setBounds(400, 35, 50, 25);
            exit.addMouseListener(this);

            con.add(addlabel);
            con.add(configure);
            con.add(exit);

            setVisible(true);
        }catch(Exception e){
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new MainUI();

    }


    public void mouseClicked(MouseEvent arg0) {
        // TODO Auto-generated method stub
        if(arg0.getSource()==addlabel){
            AddFrame add = new AddFrame(this);
            add.setVisible(true);
        }else if(arg0.getSource()==exit){
            try {
                FileWriter writetoFile = new FileWriter(savelocations);
                for (int i = 0; i < templocations.length; i++) {
                    if(templocations[i]!=null && !templocations[i][0].equals("")){
                        writetoFile.write((i+1)+";"+templocations[i][0]+";"+templocations[i][1]+"\n");
                    }
                }
                writetoFile.flush();
                writetoFile.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.exit(0);
        }else if(arg0.getSource()==configure){
            ConfigureUI confi=new ConfigureUI(this);
            if(ConfigureUI.Y==1){
                confi.setBounds(arg0.getXOnScreen(), arg0.getYOnScreen()-130, 130, 200);
            }else{
                confi.setBounds(arg0.getXOnScreen(), arg0.getYOnScreen(), 130, 200);
            }
            confi.setVisible(true);
        }
    }


    public void mouseEntered(MouseEvent arg0) {
        // TODO Auto-generated method stub
    }


    public void mouseExited(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }


    public void mousePressed(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }


    public void mouseReleased(MouseEvent arg0) {
        // TODO Auto-generated method stub
        //      largeUI.setVisible(false);
    }
}