Create a JTable based on an ArrayList containing instances of a class.

Question

I have a class, IncomeBudgetItem, instances of which are contained in an ArrayList. I would like to create a JTable, based on this ArrayList. One variable is a string, while others are type double. Not all variables are to appear in the JTable.
The internal logic of my program is already working. And my GUI is largely constructed. I'm just not sure how to make them talk to each other. The actually creation of the JTable is my biggest problem right now.

Answer 1

import java.awt.Dimension;
import java.awt.GridLayout;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;
public class TableDemo extends JPanel {
     private boolean DEBUG = false;
     public TableDemo() {
          super(new GridLayout(1, 0));
          ArrayList<MyObject> list = new ArrayList<MyObject>();
          list.add(new MyObject("Kathy", "Smith", "Snowboarding", new Integer(5),
                    new Boolean(false)));
          list.add(new MyObject("John", "Doe", "Rowing", new Integer(3),
                    new Boolean(true)));
          list.add(new MyObject("Sue", "Black", "Knitting", new Integer(2),
                    new Boolean(false)));
          list.add(new MyObject("Jane", "White", "Speed reading",
                    new Integer(20), new Boolean(true)));
          JTable table = new JTable(new MyTableModel(list));
          table.setPreferredScrollableViewportSize(new Dimension(500, 70));
          table.setFillsViewportHeight(true);
          // Create the scroll pane and add the table to it.
          JScrollPane scrollPane = new JScrollPane(table);
          // Add the scroll pane to this panel.
          add(scrollPane);
     class MyObject {
          String firstName;
          String lastName;
          String sport;
          int years;
          boolean isVeg;
          MyObject(String firstName, String lastName, String sport, int years,
                    boolean isVeg) {
               this.firstName = firstName;
               this.lastName = lastName;
               this.sport = sport;
               this.years = years;
               this.isVeg = isVeg;
     class MyTableModel extends AbstractTableModel {
          private String[] columnNames = { "First Name", "Last Name", "Sport",
                    "# of Years", "Vegetarian" };
          ArrayList<MyObject> list = null;
          MyTableModel(ArrayList<MyObject> list) {
               this.list = list;
          public int getColumnCount() {
               return columnNames.length;
          public int getRowCount() {
               return list.size();
          public String getColumnName(int col) {
               return columnNames[col];
          public Object getValueAt(int row, int col) {
               MyObject object = list.get(row);
               switch (col) {
               case 0:
                    return object.firstName;
               case 1:
                    return object.lastName;
               case 2:
                    return object.sport;
               case 3:
                    return object.years;
               case 4:
                    return object.isVeg;
               default:
                    return "unknown";
          public Class getColumnClass(int c) {
               return getValueAt(0, c).getClass();
      * Create the GUI and show it. For thread safety, this method should be
      * invoked from the event-dispatching thread.
     private static void createAndShowGUI() {
          // Create and set up the window.
          JFrame frame = new JFrame("TableDemo");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          // Create and set up the content pane.
          TableDemo newContentPane = new TableDemo();
          newContentPane.setOpaque(true); // content panes must be opaque
          frame.setContentPane(newContentPane);
          // Display the window.
          frame.pack();
          frame.setVisible(true);
     public static void main(String[] args) {
          // Schedule a job for the event-dispatching thread:
          // creating and showing this application's GUI.
          javax.swing.SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                    createAndShowGUI();
}