Unit II: Applets, AWT GUI & Event Delegation

// Using WindowAdapter with an Anonymous Inner Class to close a Frame:
frame.addWindowListener(new WindowAdapter() {
    public void windowClosing(WindowEvent e) {
        System.exit(0); // Gracefully close application
    }
});

import java.awt.*;
import java.awt.event.*;

public class StudentForm extends Frame implements ActionListener {
    Label lblTitle, lblName, lblGender, lblCity, lblResult;
    TextField tfName;
    CheckboxGroup cbg;
    Checkbox rbMale, rbFemale;
    Choice chCity;
    Button btnSubmit;

    public StudentForm() {
        // 1. Frame setup
        setTitle("Student Registration Portal");
        setSize(380, 360);
        setLayout(new FlowLayout(FlowLayout.CENTER, 15, 12));

        // 2. Instantiate controls
        lblTitle = new Label("--- Student Registration Form ---");
        lblTitle.setFont(new Font("Arial", Font.BOLD, 14));

        lblName = new Label("Full Name:");
        tfName = new TextField(22);

        lblGender = new Label("Gender:");
        cbg = new CheckboxGroup();
        rbMale = new Checkbox("Male", cbg, true);
        rbFemale = new Checkbox("Female", cbg, false);

        lblCity = new Label("Select City:");
        chCity = new Choice();
        chCity.add("Kanpur");
        chCity.add("Lucknow");
        chCity.add("Delhi");
        chCity.add("Varanasi");

        btnSubmit = new Button("Submit Application");
        lblResult = new Label("Status: Awaiting input...");

        // 3. Register Action Listener
        btnSubmit.addActionListener(this);

        // 4. Add controls to Frame
        add(lblTitle);
        add(lblName); add(tfName);
        add(lblGender); add(rbMale); add(rbFemale);
        add(lblCity); add(chCity);
        add(btnSubmit);
        add(lblResult);

        // 5. Close window via WindowAdapter
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                dispose();
            }
        });

        setVisible(true);
    }

    // Event Handler Method
    public void actionPerformed(ActionEvent e) {
        String name = tfName.getText();
        String gender = cbg.getSelectedCheckbox().getLabel();
        String city = chCity.getSelectedItem();
        lblResult.setText("Registered: " + name + " (" + gender + ", " + city + ")");
    }

    public static void main(String[] args) {
        new StudentForm();
    }
}

// File: BannerApplet.java
import java.applet.Applet;
import java.awt.Graphics;
import java.awt.Color;
import java.awt.Font;

public class BannerApplet extends Applet {
    String msg;

    public void init() {
        setBackground(Color.DARK_GRAY);
        setForeground(Color.WHITE);
        // Read external parameter passed from HTML
        msg = getParameter("city");
        if (msg == null) msg = "Kanpur";
    }

    public void paint(Graphics g) {
        g.setFont(new Font("Arial", Font.BOLD, 18));
        g.drawString("Welcome to CSJMU: " + msg, 40, 60);
        g.drawRect(30, 30, 320, 50);
    }
}

<!-- HTML file to run the applet via appletviewer -->
<html>
  <body>
    <applet code="BannerApplet.class" width="400" height="150">
      <param name="city" value="Kanpur University" />
    </applet>
  </body>
</html>

import java.applet.Applet;
import java.awt.*;

public class HutApplet extends Applet {
    public void paint(Graphics g) {
        // 1. Draw Roof (Triangle via drawPolygon)
        int[] xRoof = {150, 80, 220};
        int[] yRoof = {50, 110, 110};
        g.setColor(Color.RED);
        g.fillPolygon(xRoof, yRoof, 3);

        // 2. Draw House Walls (Rectangle)
        g.setColor(Color.ORANGE);
        g.fillRect(90, 110, 120, 100);

        // 3. Draw Door & Window
        g.setColor(Color.DARK_GRAY);
        g.fillRect(135, 150, 30, 60); // Door
        g.setColor(Color.CYAN);
        g.fillRect(105, 125, 25, 25); // Left window
        g.fillRect(170, 125, 25, 25); // Right window

        // 4. Draw Right-Angled Triangle via drawLine
        g.setColor(Color.BLUE);
        g.drawLine(250, 110, 250, 210); // Vertical
        g.drawLine(250, 210, 310, 210); // Base
        g.drawLine(250, 110, 310, 210); // Hypotenuse
    }
}