GUI Programming in Java BCA Semester 2 Unit 5

Prepared By: Uday Shah 

Ruparel Education Pvt. Ltd – (HOD-IT)

Asst. Prof., 

Faculty of Computer Applications,

Nobile University

Unit 5 – Introduction to Java

1. Explain the architecture of Swing.

Swing is a part of Java Foundation Classes (JFC) used to create graphical user interface (GUI) applications. It provides ready-made components like buttons, labels, text fields, tables, menus, etc. Swing is built on top of AWT (Abstract Window Toolkit), so it uses AWT’s basic window features but gives more advanced controls.

The architecture of Swing follows a Model-View-Controller (MVC) design pattern. In this pattern, the Model stores data, the View displays data on the screen, and the Controller handles user actions such as clicking buttons or typing text.

For example, in a JTextField, the text entered by the user is stored in the model, the textbox shown on screen is the view, and keyboard actions are controlled by the controller.

Swing components are lightweight because they are written in Java and do not depend fully on the operating system. This allows Swing applications to look similar on Windows, Linux, and Mac.

Basic Swing hierarchy:

Object

 └── Component

      └── Container

           └── JComponent

                ├── JButton

                ├── JLabel

                ├── JTextField

                 └── JTable

Example:

import javax.swing.*;

class Demo {

    public static void main(String args[]) {

        JFrame f = new JFrame("Swing Example");

        JButton b = new JButton("Click");

        b.setBounds(100,100,100,30);

        f.add(b);

        f.setSize(300,300);

        f.setLayout(null);

        f.setVisible(true);

    }

}

2. Differentiate between AWT and Swing.

AWT stands for Abstract Window Toolkit. It is Java’s first GUI library. Swing is a newer and improved GUI library developed as part of JFC. Swing is built on top of AWT.

AWT components are heavyweight, meaning they use native operating system components. Swing components are lightweight, meaning they are mostly written in Java and do not depend on OS components.

Swing provides more controls such as JTable, JTree, JTabbedPane, JColorChooser, etc. AWT has limited controls like Button, Label, TextField, Checkbox.

Swing supports pluggable look and feel, so the design can be changed. AWT uses fixed OS look and feel.

 

Feature	AWT	Swing
Full Form	Abstract Window Toolkit	Part of Java Foundation Classes
Components	Heavyweight	Lightweight
Look	Native OS Look	Customizable
Controls	Limited	Rich Controls
Speed	Faster sometimes	Slightly slower

Example:

// AWT

Button b = new Button("OK");

 

// Swing

JButton b = new JButton("OK");

 

3. Explain the Swing lightweight component model.

Swing components are called lightweight components because they do not use separate native screen resources from the operating system. They are drawn by Java itself.

For example, when a JButton is displayed, Java paints it using code instead of asking Windows or Linux to create a real OS button. Because of this, Swing components look similar on every platform.

Lightweight components reduce dependency on operating system design. This gives flexibility in appearance and behavior. Java can easily change colors, themes, fonts, borders, and styles.

All Swing components except top-level containers like JFrame, JDialog, and JWindow are lightweight. These top-level containers are heavyweight because they need OS windows.

Advantages of lightweight model:

• Same look on all platforms
• Rich GUI design
• Custom painting possible
• Easy theme support
• Better portability

Example:

JButton btn = new JButton("Save");

JLabel lbl = new JLabel("Name");

These are lightweight Swing components.

 

4. Describe the role of layout managers in Java.

A layout manager is used to arrange GUI components automatically inside a container such as a frame, panel, or JFRAME. It controls the position and size of buttons, labels, text fields, etc.

Instead of manually giving coordinates, layout managers organise components properly even when the window size changes. This makes the GUI flexible and professional.

Java provides many layout managers, such as the following:

• FlowLayout
• BorderLayout
• GridLayout
• CardLayout
• GridBagLayout

For example, if you resize a window, the layout manager automatically adjusts components according to available space.

Without a layout manager:

setLayout(null);

button.setBounds(10, 20, 100, 30);

With layout manager:

setLayout(new FlowLayout());

add(button);

Advantages:

• Easy GUI design
• Automatic resizing
• Platform independent
• Less coding
• Better alignment

 

5. Explain FlowLayout with a suitable example.

FlowLayout is the default layout manager for Panel and JPanel. It places components in a row from left to right, similar to words in a paragraph.

When one row becomes full, components automatically move to the next row. It is simple and useful for small forms.

FlowLayout supports alignment:

• LEFT
• CENTER
• RIGHT

Syntax:

setLayout(new FlowLayout());

Example:

import javax.swing.*;

import java.awt.*;

class FlowDemo {

    public static void main(String args[]) {

        JFrame f = new JFrame();

        f.setLayout(new FlowLayout());

        f.add(new JButton("One"));

        f.add(new JButton("Two"));

        f.add(new JButton("Three"));

        f.setSize(300,200);

        f.setVisible(true);

    }

}

Output:

[One] [Two] [Three]

 

6. Explain BorderLayout with its regions.

BorderLayout divides a container into five regions. It is the default layout for the JFrame content pane.

The five regions are:

• North
• South
• East
• West
• Center

Diagram:

NORTH
WEST	CENTER	EAST
SOUTH

Only one component can be added to each region. If no region is given, the component goes to the center.

Example:

setLayout(new BorderLayout());

 

add(new JButton("Top"), BorderLayout.NORTH);

add(new JButton("Bottom"), BorderLayout.SOUTH);

add(new JButton("Left"), BorderLayout.WEST);

add(new JButton("Right"), BorderLayout.EAST);

add(new JButton("Center"), BorderLayout.CENTER);

It is useful for the main window design.

 

 

7. Explain GridLayout with a diagram.

GridLayout arranges components in rows and columns like a table. Every cell has an equal size.

It is useful when many buttons need equal arrangement, such as a calculator keypad or a login form.

Syntax:

setLayout(new GridLayout(rows, columns));

Diagram for GridLayout(2,3):

C1	C2	C3
C4	C5	C6

Example:

setLayout(new GridLayout(2, 2));

 

add(new JButton("1"));

add(new JButton("2"));

add(new JButton("3"));

add(new JButton("4"));

Advantages:

• Equal-sized components
• Neat arrangement
• Easy to use

 

8. Write a short note on JMenuBar, JMenu, and JMenuItem.

These classes are used to create menus in Swing applications.

JMenuBar is the top menu bar placed in a frame. It contains multiple menus like File, Edit, and Help.

JMenu represents one menu inside the menu bar. Example: File menu.

A JMenuItem represents items inside a menu, such as Open, Save, and Exit.

Hierarchy:

JMenuBar

   ├── JMenu (File)

   │      ├── JMenuItem(Open)

   │      └── JMenuItem(Save)

Example:

JMenuBar mb = new JMenuBar();

JMenu file = new JMenu("File");

JMenuItem open = new JMenuItem("Open");

 

file.add(open);

mb.add(file);

frame.setJMenuBar(mb);

 

9. Explain the Graphics class in Java.

The graphics class is used for drawing shapes, text, and images in Java GUI applications.

It provides methods like the following:

• drawLine()
• drawRect()
• drawOval()
• drawString()
• fillRect()

A graphics object is automatically passed to paint() or paintComponent() methods.

Example:

public void paint(Graphics g) {

    g.drawLine(50,50,150,50);

    g.drawRect(50,70,100,50);

    g.drawString("Hello", 80, 150);

}

Uses:

• Drawing diagrams
• Custom design
• Charts
• Animation basics

13. Explain MouseEvent with an example.

A mouse event occurs when the user uses the mouse in a GUI application.

Common mouse events:

• mouseClicked()
• mousePressed()
• mouseReleased()
• mouseEntered()
• mouseExited()

The MouseEvent object gives information like:

• X and Y position
• Click count
• Which button pressed

Example:

import javax.swing.*;

import java.awt.event.*;

 

class Demo extends JFrame implements MouseListener {

 

    Demo() {

        addMouseListener(this);

        setSize(300,300);

        setVisible(true);

    }

 

    public void mouseClicked(MouseEvent e) {

        System.out.println("X = " + e.getX());

        System.out.println("Y = " + e.getY());

    }

 

    public void mousePressed(MouseEvent e){}

    public void mouseReleased(MouseEvent e){}

    public void mouseEntered(MouseEvent e){}

    public void mouseExited(MouseEvent e){}

    public static void main(String args[]) {

        new Demo();

    }

}

When user clicks inside frame, mouse position is displayed.

::Best of Luck ::