How Can I Create Dynamically Populated JComboBoxes in Java?

Interactive JComboBoxes for Dynamic Data Display

In this programming scenario, you're presented with a structured data set of courses and their corresponding options. Your goal is to create two JComboBoxes that enable dynamic population of options based on the selection made in the first JComboBox.

Dynamic ComboBox Implementation

To achieve this, you'll need to employ a DefaultComboBoxModel for each set of options. When a user selects an item from the first JComboBox (JComboBox1), you'll set the model for the second JComboBox (JComboBox2) to correspond with the selected option.

Implementation Example

Consider the following Java code, which demonstrates this implementation:

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ComboTest extends JPanel implements ActionListener, Runnable {
    // Create JComboBoxes and ComboBoxModels
    private final JComboBox combo1 = new JComboBox(new String[]{"Course 1", "Course 2", "Course 3"});
    private final JComboBox combo2 = new JComboBox();
    private ComboBoxModel[] models = new ComboBoxModel[3];

    public ComboTest() {
        // Initialize ComboBoxModels with corresponding data
        models[0] = new DefaultComboBoxModel(new String[]{"A1", "A2"});
        models[1] = new DefaultComboBoxModel(new String[]{"B1", "B2", "B3", "B4"});
        models[2] = new DefaultComboBoxModel(new String[]{"C1", "C2"});

        // Set initial model for combo2
        combo2.setModel(models[0]);
        this.add(combo1);
        this.add(combo2);
        // Add action listener to listen for selections in combo1
        combo1.addActionListener(this);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // Get the selected index in combo1
        int i = combo1.getSelectedIndex();
        // Update the model in combo2 with the corresponding model
        combo2.setModel(models[i]);
    }

    // Main method for initializing the GUI
    @Override
    public void run() {
        JFrame f = new JFrame("ComboTest");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new ComboTest());
    }
}

By implementing this approach, you can dynamically populate combo boxes and provide an interactive user experience for selecting data options.

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