What is Java JRadioButton?

In Java, a JRadioButton is a component from the Swing library that allows the user to select one option from a set of mutually exclusive choices. JRadioButtons are typically used in forms or applications where only one choice can be selected at a time, such as in a list of radio buttons representing different options or preferences.

Key Features of JRadioButton:

• Exclusive Selection: Only one radio button in a group can be selected at a time. If you select a new radio button in the group, the previously selected one will be deselected automatically.
• Part of ButtonGroup: JRadioButtons are usually added to a ButtonGroup to manage their mutual exclusivity. When added to a ButtonGroup, selecting one radio button will automatically deselect others in the same group.
• Visibility: A JRadioButton can have a label (text) associated with it, and it can be either selected or unselected by the user.

Creating and Using JRadioButton in Java:

1. Basic Example:

Here’s a simple example where we create a few radio buttons and add them to a ButtonGroup so that only one of them can be selected at a time.

import javax.swing.*;
import java.awt.*;

public class RadioButtonExample {
    public static void main(String[] args) {
        // Create the frame
        JFrame frame = new JFrame("JRadioButton Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);

        // Create radio buttons
        JRadioButton option1 = new JRadioButton("Option 1");
        JRadioButton option2 = new JRadioButton("Option 2");
        JRadioButton option3 = new JRadioButton("Option 3");

        // Create a ButtonGroup to group the radio buttons
        ButtonGroup group = new ButtonGroup();
        group.add(option1);
        group.add(option2);
        group.add(option3);

        // Create a panel to add the radio buttons
        JPanel panel = new JPanel();
        panel.add(option1);
        panel.add(option2);
        panel.add(option3);

        // Add the panel to the frame
        frame.add(panel);

        // Set the frame visibility
        frame.setVisible(true);
    }
}

Key Steps in the Example:

• Creating JRadioButton: We create instances of JRadioButton with the desired labels.
• Adding to ButtonGroup: We use ButtonGroup to ensure that only one radio button can be selected at a time.
• Adding to JFrame: The radio buttons are added to a JPanel, which is then added to the JFrame to display the GUI.

2. Handling Events with JRadioButton:

You can also handle events for a JRadioButton (like when the user selects or deselects it) by adding an ActionListener to the radio button.

Here’s an example:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class RadioButtonActionExample {
    public static void main(String[] args) {
        // Create the frame
        JFrame frame = new JFrame("JRadioButton Action Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);

        // Create radio buttons
        JRadioButton option1 = new JRadioButton("Option 1");
        JRadioButton option2 = new JRadioButton("Option 2");
        JRadioButton option3 = new JRadioButton("Option 3");

        // Create a ButtonGroup
        ButtonGroup group = new ButtonGroup();
        group.add(option1);
        group.add(option2);
        group.add(option3);

        // Add ActionListener to handle selection changes
        option1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (option1.isSelected()) {
                    System.out.println("Option 1 Selected");
                }
            }
        });

        option2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (option2.isSelected()) {
                    System.out.println("Option 2 Selected");
                }
            }
        });

        option3.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (option3.isSelected()) {
                    System.out.println("Option 3 Selected");
                }
            }
        });

        // Create a panel to add radio buttons
        JPanel panel = new JPanel();
        panel.add(option1);
        panel.add(option2);
        panel.add(option3);

        // Add the panel to the frame
        frame.add(panel);

        // Set frame visibility
        frame.setVisible(true);
    }
}

Key Points in the Example:

• ActionListener: Each radio button has an ActionListener added to it to detect when the radio button is selected.
• Checking Selection: We use isSelected() to check if the radio button is selected when the action event occurs.

Methods of JRadioButton:

1. setSelected(boolean selected): This method allows you to programmatically select or deselect a JRadioButton.

   option1.setSelected(true); // Selects the radio button
   

2. isSelected(): This method returns a boolean value indicating whether the radio button is selected or not.

   if (option1.isSelected()) {
       System.out.println("Option 1 is selected.");
   }
   

3. setText(String text): Sets or changes the label of the radio button.

   option1.setText("New Label for Option 1");
   

4. setEnabled(boolean enabled): This method enables or disables the radio button.

   option1.setEnabled(false); // Disables the radio button
   

5. setToolTipText(String text): This sets a tooltip that appears when the user hovers over the radio button.

   option1.setToolTipText("Click to select this option");
   

Conclusion:

• JRadioButton is a Swing component used for providing mutually exclusive options in a graphical user interface (GUI).
• It can be grouped together with other JRadioButton components using a ButtonGroup to ensure that only one option is selected at a time.
• It can be customized with text, selected states, and event listeners to provide interactivity.
• ActionListener or other listeners can be used to handle user interaction with the radio buttons, enabling dynamic behavior in the application.

By combining JRadioButton with other Swing components like JFrame, JPanel, and ButtonGroup, you can build rich and interactive GUI applications.