Hey guys..I am not able to find the solution of the problem in my applet. It displays the buttons for only one category and it is not going ahead with the program.
Please help me find the problem and solution...
My program is.....

import java.awt.*;     //Basic hierarchy of packages for native GUI components
import java.applet.*;    //Package for creating an applet
import java.awt.event.*; 
import java.awt.event.MouseListener;
public  class App extends Applet implements MouseListener 
{
    String HY="Head Boy";
    String HL="Head Girl";
    String SY="Sports Prefect Boy";
    String SL="Sports Prefect Girl";
    String CHC="Cheetah House Captain";
    String CHVC="Cheetah House Vice-Captain";
 
    String HB11="Arnav Kholkar";
    String HB12="Chinmay Patwardhan";
    String HB13="Ishan Joshi";
    String HB14="Sumedh Sontakke";
 
    String HG11="Avani Awasthee";
    String HG12="Chaiti Bhagwat";
    String HG13="Rucha Kalekar";
    String HG14="Smruti Pimplikar";
 
    String SPB11="Anuj Kankaria";
    String SPB12="Arnav Kholkar";
    String SPB13="Chinmay Patwardhan";
    String SPB14="Yogesh Sirvi";
 
    String SPG11="Disha Trivedi";
    String SPG12="Manasi Gokhale";
    String SPG13="Shivani Gupta";
    String SPG14="Shruti Jani";
 
    String C11="Shaunak Chitgopkar";
    String C12="Shivani Gupta";
    String C13="Smruti Pimplikar";
    String C14="Surinder Mathrani";
 
    String VC11="Arya Prabhudesai";
    String VC12="Atharva Mahajan";
    String VC13="Chinmay Kalluraya";
    String VC14="Manasi Deshpande";
 
    int HB1,HB2,HB3,HB4,HG1,HG2,HG3,HG4,SPB1,SPB2,SPB3,SPB4,SPG1,SPG2,SPG3,SPG4,C1,C2,C3,C4,VC1,VC2,VC3,VC4;
    int tie; //Variable that checks whether two or more candidates received the same number of votes. 
    Font font;   //Allows the message to be printed in a specific font 
    Button button,H1,H2,H3,H4; //The buttons used for selecting the choice    
    Label label,title,HB,HG;
    Panel P1,P2,P3,P4; // area where the buttons can be displayed
    public void init() //Initialising Method for Applet
    {
        addMouseListener(this);
        setLayout (new BorderLayout ());
        P1 = new Panel (new BorderLayout ());
        P2 = new Panel (); 
        P3 = new Panel ();
        P4 = new Panel ();
        font = new Font ("ComicSans", Font.BOLD, 17);
        setFont (font);
        this.setBackground(Color.yellow);
        label= new Label("Welcome to Vidya Valley School Elections");
        HB = new Label (HY);
        HG= new Label(HL);
        HB.addMouseListener (this);
        add (P1, "North");
        P1.add (P2, "North");
        P2.add (label);
        label.setBackground(Color.black);
        label.setForeground(Color.green);
        HB.setBackground(Color.white);
        HB.setForeground(Color.black);
        H1= new Button (HB11);
        H1.addMouseListener (this);
        H2= new Button (HB12);
        H2.addMouseListener (this);
        H3= new Button (HB13);
        H3.addMouseListener (this);
        H4= new Button (HB14);
        H4.addMouseListener (this);
        P1.add (P3,"West");
        P3.add (HB);
        P3.add (H1);
        P3.add (H2);
        P3.add (H3);
        P3.add (H4);
    }
 
    public void mouseClicked(MouseEvent e)
    {
        if(e.getSource () == H1)
        {
            P1.add(P4,"West");
            P4.add(HG);
        }
    }
    // methods used for applet installment and destruction
    public void start() 
    {
        System.out.println(" Applet Starting ");
    }
 
    public void stop() 
    {
        System.out.println(" Applet Stopping ");
    }
 
    public void destroy() 
    {
        System.out.println(" Applet Destroyed ");
    }
 
    //These are not used but are necessary for mouseListener
    public void mouseEntered (MouseEvent e)
    {
    }
 
    public void mouseExited (MouseEvent e)
    {
    }
 
    public void mousePressed (MouseEvent e)
    {
    }
 
    public void mouseReleased (MouseEvent e)
    {
    }
 
}