How to Set a Custom Object in a JTable Row in Java

Question

How can I set a custom object as a value in a JTable row in Java?

JTable table = new JTable();
MyCustomObject myObject = new MyCustomObject();
TableModel model = table.getModel();
model.setValueAt(myObject, row, column);

Answer

In Java Swing, a JTable allows you to display tabular data, which can include custom objects. To set a custom object in a JTable row, you need to define a custom table model that handles your object's properties appropriately. This ensures that the JTable can correctly display your custom object and its associated data.

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

class MyCustomObject {
    private String name;
    private int value;

    public MyCustomObject(String name, int value) {
        this.name = name;
        this.value = value;
    }

    public String getName() { return name; }
    public int getValue() { return value; }
}

class MyTableModel extends AbstractTableModel {
    private List<MyCustomObject> data;
    private String[] columnNames = {"Name", "Value"};

    public MyTableModel(List<MyCustomObject> data) {
        this.data = data;
    }

    @Override
    public int getColumnCount() { return columnNames.length; }

    @Override
    public int getRowCount() { return data.size(); }

    @Override
    public Object getValueAt(int rowIndex, int columnIndex) {
        MyCustomObject obj = data.get(rowIndex);
        if (columnIndex == 0) return obj.getName();
        if (columnIndex == 1) return obj.getValue();
        return null;
    }

    @Override
    public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
        MyCustomObject obj = data.get(rowIndex);
        if (columnIndex == 0) obj.setName((String) aValue);
        if (columnIndex == 1) obj.setValue((Integer) aValue);
        fireTableCellUpdated(rowIndex, columnIndex);
    }
}

List<MyCustomObject> dataList = new ArrayList<>();
dataList.add(new MyCustomObject("Object1", 10));
JTable table = new JTable(new MyTableModel(dataList));
JScrollPane scrollPane = new JScrollPane(table);

Causes

The default table model of JTable does not know how to display custom objects directly.
You need to implement a custom TableModel or DefaultTableModel to manage your custom objects.

Solutions

Create a class that extends AbstractTableModel to define how to handle your custom objects.
Override the methods such as getColumnCount(), getRowCount(), getValueAt(), and setValueAt() to manage object properties.
Use the custom model in your JTable instance.

Common Mistakes

Mistake: Not overriding the getColumnClass method in the TableModel.

Solution: Override getColumnClass to ensure that JTable handles custom object classes correctly.

Mistake: Failing to call fireTableDataChanged after changing data in the model.

Solution: Always call fireTableDataChanged or related methods to refresh the JTable after data updates.

Helpers

JTable
Java JTable custom object
set custom object JTable
Java Swing
next steps for JTable
JTable examples