JTable and Table Models

📝 JTable and Table Models in Java Swing 🎯

---

🎯 What is a JTable?

JTable is a powerful Swing component for displaying data in a table format, which is ideal for organizing and managing structured data such as spreadsheets or databases. It allows users to view and interact with rows and columns of data.

---

✅ Features of JTable:

• Editable Cells: Users can modify the data in each cell.
• Customizable Columns and Rows: You can add, remove, and customize columns and rows.
• Dynamic Updates: Easily update the table's content during runtime.
• Scrollable Table: Supports horizontal and vertical scrolling if the table is too large to fit the screen.

---

📚 Step 1: Creating a Basic JTable

---

📝 Example: Creating a Basic JTable

import javax.swing.*;
import javax.swing.table.DefaultTableModel;

public class JTableExample {
    public static void main(String[] args) {
        // Create JFrame
        JFrame frame = new JFrame("JTable Example");

        // Column Names for the JTable
        String[] columns = {"ID", "Name", "Age"};

        // Data for the JTable
        Object[][] data = {
            {1, "Alice", 24},
            {2, "Bob", 30},
            {3, "Charlie", 22},
            {4, "David", 35}
        };

        // Create JTable with the data and column names
        JTable table = new JTable(data, columns);

        // Add JTable to JScrollPane for scroll support
        JScrollPane scrollPane = new JScrollPane(table);

        // Set layout and add JScrollPane to frame
        frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
        frame.add(scrollPane);

        // Set frame properties
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

---

🎨 Explanation

✅ String[] columns = {"ID", "Name", "Age"};

• This defines the column names that will appear at the top of the table.

✅ Object[][] data = {{1, "Alice", 24}, {2, "Bob", 30}, ...};

• This is the data for the table. Each row contains values for the "ID", "Name", and "Age" columns.

✅ JTable table = new JTable(data, columns);

• This creates the table with the specified data and columns.

---

👩‍🎨 Output:

+-----+---------+-----+
| ID  | Name    | Age |
+-----+---------+-----+
| 1   | Alice   | 24  |
| 2   | Bob     | 30  |
| 3   | Charlie | 22  |
| 4   | David   | 35  |
+-----+---------+-----+

---

🎯 Step 2: Making JTable Editable

By default, the cells in a JTable are not editable. You can enable cell editing so that users can modify the data in the table.

---

📝 Example: Making JTable Editable

import javax.swing.*;
import javax.swing.table.DefaultTableModel;

public class EditableJTable {
    public static void main(String[] args) {
        // Create JFrame
        JFrame frame = new JFrame("Editable JTable");

        // Column Names for the JTable
        String[] columns = {"ID", "Name", "Age"};

        // Data for the JTable
        Object[][] data = {
            {1, "Alice", 24},
            {2, "Bob", 30},
            {3, "Charlie", 22},
            {4, "David", 35}
        };

        // Create DefaultTableModel with data and columns
        DefaultTableModel model = new DefaultTableModel(data, columns);
        
        // Create JTable with the model
        JTable table = new JTable(model);

        // Add JTable to JScrollPane for scroll support
        JScrollPane scrollPane = new JScrollPane(table);

        // Set layout and add JScrollPane to frame
        frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
        frame.add(scrollPane);

        // Set frame properties
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

---

🎨 Explanation

✅ DefaultTableModel model = new DefaultTableModel(data, columns);

• This model allows the data to be editable. Each cell can be clicked and edited by the user.

---

👩‍🎨 Output:

• The table will be editable, and you can change any of the values in the cells.

---

🎯 Step 3: Using Table Models with JTable

A TableModel provides an interface to handle the data behind a JTable. You can use a custom TableModel to have more control over the data structure and its behavior.

---

📝 Example: Using a Custom TableModel

import javax.swing.*;
import javax.swing.table.AbstractTableModel;

public class CustomTableModelExample {
    public static void main(String[] args) {
        // Create JFrame
        JFrame frame = new JFrame("Custom TableModel Example");

        // Create a custom table model
        MyTableModel model = new MyTableModel();

        // Create JTable with custom model
        JTable table = new JTable(model);

        // Add JTable to JScrollPane for scroll support
        JScrollPane scrollPane = new JScrollPane(table);

        // Set layout and add JScrollPane to frame
        frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
        frame.add(scrollPane);

        // Set frame properties
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    // Custom TableModel class
    static class MyTableModel extends AbstractTableModel {
        // Column names
        String[] columns = {"ID", "Name", "Age"};

        // Data for the table
        Object[][] data = {
            {1, "Alice", 24},
            {2, "Bob", 30},
            {3, "Charlie", 22},
            {4, "David", 35}
        };

        @Override
        public int getColumnCount() {
            return columns.length;  // Number of columns
        }

        @Override
        public int getRowCount() {
            return data.length;  // Number of rows
        }

        @Override
        public Object getValueAt(int rowIndex, int columnIndex) {
            return data[rowIndex][columnIndex];  // Return the value at the specified cell
        }

        @Override
        public String getColumnName(int column) {
            return columns[column];  // Return column name
        }
    }
}

---

🎨 Explanation

✅ AbstractTableModel

• AbstractTableModel is a class that you can extend to create custom table models. You define how to get the data and column names.

✅ getValueAt(int rowIndex, int columnIndex)

• This method returns the value at the specified row and column index.

✅ getColumnCount()

• Returns the number of columns in the table.

✅ getRowCount()

• Returns the number of rows in the table.

---

👩‍🎨 Output:

+-----+---------+-----+
| ID  | Name    | Age |
+-----+---------+-----+
| 1   | Alice   | 24  |
| 2   | Bob     | 30  |
| 3   | Charlie | 22  |
| 4   | David   | 35  |
+-----+---------+-----+

---

🎯 Step 4: Handling Table Events

You can listen to events like row selection or cell editing in a JTable using listeners.

---

📝 Example: Handling Table Row Selection

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.DefaultTableModel;

public class JTableRowSelection {
    public static void main(String[] args) {
        // Create JFrame
        JFrame frame = new JFrame("Row Selection Example");

        // Column Names
        String[] columns = {"ID", "Name", "Age"};

        // Data
        Object[][] data = {
            {1, "Alice", 24},
            {2, "Bob", 30},
            {3, "Charlie", 22},
            {4, "David", 35}
        };

        // Create DefaultTableModel
        DefaultTableModel model = new DefaultTableModel(data, columns);

        // Create JTable
        JTable table = new JTable(model);

        // Add ListSelectionListener to handle row selection
        table.getSelectionModel().addListSelectionListener(e -> {
            if (!e.getValueIsAdjusting()) {
                int selectedRow = table.getSelectedRow();
                System.out.println("Selected Row: " + selectedRow);
            }
        });

        // Add JTable to JScrollPane
        JScrollPane scrollPane = new JScrollPane(table);

        // Set layout and add JScrollPane to frame
        frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
        frame.add(scrollPane);

        // Set frame properties
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

---

🎨 Explanation

✅ table.getSelectionModel().addListSelectionListener(e -> {...});

• This adds a listener to detect when a row is selected, and the row index is printed in the console.

---

👩‍🎨 Output:

(When Row 2 is selected)
Selected Row: 2