| Types java app |
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| Data Types and Operators |
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| (Primitive Data Types) |
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| (Non-Primitive Data Types) |
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| Control Flow Statements |
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| Conditional Statements |
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| Looping Statements |
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| Branching Statements |
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| Object-Oriented Programming (OOP) |
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| Classes and Objects |
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| Inheritance |
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| Polymorphism |
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| Encapsulation |
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| Abstraction |
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| Exception Handling |
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| Introduction to Exceptions |
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| Collections Framework |
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| Overview of Collections |
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| Commonly Used Collections |
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| Iterators |
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| Java I/O |
|---|
| File Handling |
|---|
| Serialization |
|---|
| Multithreading |
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| Introduction to Threads |
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| Thread Synchronization |
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| GUI Programming with Swing |
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| Introduction to Swing |
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| Event Handling |
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| Advanced Topics |
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| Java Database Connectivity (JDBC) |
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| JAVA CODE |
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Java Basics
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Working with Objects
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Arrays, Conditionals, and Loops
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Creating Classes and Applications in Java
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More About Methods
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Java Applet Basics
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Graphics, Fonts, and Color
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Simple Animation and Threads
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More Animation, Images, and Sound
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Managing Simple Events and Interactivity
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Creating User Interfaces with the awt
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Windows, Networking, and Other Tidbits
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Modifiers, Access Control, and Class Design
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Packages and Interfaces
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Exceptions
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Multithreading
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Streams and I/O
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Using Native Methods and Libraries
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Under the Hood
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Java Programming Tools
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Working with Data Structures in Java
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Advanced Animation and Media
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Fun with Image Filters
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Client/Server Networking in Java
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Emerging Technologies
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appendix A :- Language Summary
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appendix B :- Class Hierarchy Diagrams
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appendix C The Java Class Library
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appendix D Bytecodes Reference
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appendix E java.applet Package Reference
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appendix F java.awt Package Reference
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appendix G java.awt.image Package Reference
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appendix H java.awt.peer Package Reference
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appendix I java.io Package Reference
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appendix J java.lang Package Reference
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appendix K java.net Package Reference
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appendix L java.util Package Reference
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Handling events in GUI (Graphical User Interface) applications in Java involves responding to user interactions such as button clicks, mouse movements, keyboard inputs, and other actions. Java provides a rich set of libraries and classes to handle these events, primarily through the Abstract Window Toolkit (AWT) and Swing frameworks. Here, we’ll delve into how events are handled in Java GUI applications using these frameworks, with examples to illustrate the concepts.
Event Handling in Java
Event handling in Java involves three main components:
- Event Source: The GUI component that generates the event (e.g., a button).
- Event Object: The object that encapsulates information about the event (e.g., ‘
ActionEvent‘, ‘MouseEvent‘). - Event Listener: The object that listens for and processes the event.
Basic Steps for Event Handling
- Identify the event source.
- Implement the event listener interface.
- Register the event listener with the event source.
Example: Handling a Button Click Event
Let’s start with a simple example where we handle a button click event in a Swing application.
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class ButtonClickExample {
public static void main(String[] args) {
// Create a new JFrame (window)
JFrame frame = new JFrame("Button Click Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(300, 200);
// Create a new JButton (button)
JButton button = new JButton("Click Me!");
// Create a new label to display the message
JLabel label = new JLabel("Button not clicked yet.");
// Add ActionListener to the button
button.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// Update the label when the button is clicked
label.setText("Button clicked!");
}
});
// Add the button and label to the frame's content pane
frame.getContentPane().add(button, "North");
frame.getContentPane().add(label, "South");
// Display the frame
frame.setVisible(true);
}
}
- A ‘
JButton‘ is created and added to aJFrame. - An ‘
ActionListener‘ is registered with the button. The ‘actionPerformed‘ method is overridden to update the label when the button is clicked.
Handling Mouse Events
Here’s an example that handles mouse events, such as mouse clicks, movements, and drags.
import javax.swing.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
public class MouseEventExample {
public static void main(String[] args) {
// Create a new JFrame
JFrame frame = new JFrame("Mouse Event Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 300);
// Create a new JLabel to display mouse events
JLabel label = new JLabel("Move or click the mouse.");
// Add MouseListener and MouseMotionListener to the frame
frame.addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
label.setText("Mouse clicked at (" + e.getX() + ", " + e.getY() + ")");
}
@Override
public void mouseEntered(MouseEvent e) {
label.setText("Mouse entered the frame.");
}
@Override
public void mouseExited(MouseEvent e) {
label.setText("Mouse exited the frame.");
}
});
frame.addMouseMotionListener(new MouseAdapter() {
@Override
public void mouseMoved(MouseEvent e) {
label.setText("Mouse moved to (" + e.getX() + ", " + e.getY() + ")");
}
});
// Add the label to the frame's content pane
frame.getContentPane().add(label);
// Display the frame
frame.setVisible(true);
}
}
- The
MouseAdapterclass is used to handle various mouse events. - Mouse click, enter, exit, and move events are captured and displayed on a
JLabel.
Handling Keyboard Events
Let’s look at an example that handles keyboard events.
import javax.swing.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
public class KeyEventExample {
public static void main(String[] args) {
// Create a new JFrame
JFrame frame = new JFrame("Key Event Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 300);
// Create a new JTextArea to display key events
JTextArea textArea = new JTextArea("Type something...");
// Add KeyListener to the text area
textArea.addKeyListener(new KeyAdapter() {
@Override
public void keyTyped(KeyEvent e) {
char keyChar = e.getKeyChar();
textArea.append("\nKey Typed: " + keyChar);
}
@Override
public void keyPressed(KeyEvent e) {
int keyCode = e.getKeyCode();
textArea.append("\nKey Pressed: " + KeyEvent.getKeyText(keyCode));
}
@Override
public void keyReleased(KeyEvent e) {
int keyCode = e.getKeyCode();
textArea.append("\nKey Released: " + KeyEvent.getKeyText(keyCode));
}
});
// Add the text area to the frame's content pane
frame.getContentPane().add(new JScrollPane(textArea));
// Display the frame
frame.setVisible(true);
}
}
- The
KeyAdapterclass is used to handle keyboard events. - Key typed, pressed, and released events are captured and displayed in a
JTextArea.
Event handling is a crucial aspect of Java GUI applications. By understanding how to work with event sources, event objects, and event listeners, you can create responsive and interactive applications. The examples provided illustrate basic event handling for buttons, mouse events, and keyboard events, which are common in many GUI applications.
