Changing Columns in JTable using JRadioButtons doesn't refresh structure

Question 1

In your example, you are not registering an ActionListener to profsBtn or officeSpBtn, you keep registering to coursesBtn

JRadioButton coursesBtn = new JRadioButton("Courses");
//...
coursesBtn.addActionListener(this);

JRadioButton profsBtn = new JRadioButton("Professors");
//...
coursesBtn.addActionListener(this);

JRadioButton officeSpBtn = new JRadioButton("Office Spaces");
//...
coursesBtn.addActionListener(this);

Once I register the ActionListener to the correct buttons, it works fine

Question 2

The problem seems to be that the code adds the listener 3 times to a single button, rather than once each to each of the 3 buttons!

..my application is for a very limited scope and can do without a layout manager for my purposes, unless you think this is affecting the table's behaviour?

No, not the table. It was however causing the emptyLabel to be assigned no space in the layout. Here is a robust, resizable version of the GUI.

enter image description here

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.table.*;
import java.util.*;

public class test1 implements ActionListener {

private boolean payrollActive = false;

private JPanel mainPanel = new JPanel(new BorderLayout(5,5));
private JTable dataTable;

private Vector<String> courseColumns = new Vector<String>();
private Vector<String> courseColumnsPay = new Vector<String>();
private Vector<String> profsColumns = new Vector<String>();
private Vector<String> offSpaceColumns = new Vector<String>();

public test1() {
    mainPanel.setBorder(new EmptyBorder(5,5,5,5));
    //Add columns for tables
    String[] courseColsPay = {"Year", "Program", "Course", "Code", "CCCode",
            "Weight", "Session", "Section", "Day", "STime", "FTime",
            "BookedRM", "EnrolCap", "Description", "ProfFName",
            "ProfLName", "ProfEmail", "Notes", "Syllabus", "Exam",
            "CrossList", "PreReqs", "EnrolCtrls", "Shared",
            "TrackChanges", "Address", "WageType", "BasePay",
            "BenefitRate", "Budgeted", "PayAmount",
            "MthAmount", "Term", "AccNumber", "PayAdmin", "PayableTo"};
    for (String col : courseColsPay) {
        courseColumnsPay.add(col);
    }
    for (int i = 0; i < 25; i++) {
        courseColumns.add(courseColsPay[i]);
    }
    String[] profCols = {"FName", "LName", "Email", "UTEmail", "Birthdate",
            "OfficeBC", "OfficeRM", "Department", "Status",
            "Fellowship", "OfficeStat", "PhoneNum", "HomeAddr",
            "HomePhoneNum", "Notes"};
    for (String col : profCols) {
        profsColumns.add(col);
    }
    String[] offSpaceCols = {"Building", "DeptID", "DivisionName", "BldgID", "RoomID",
            "Category", "Description", "ShareType", "DeptName",
            "Status", "SharePerc", "ShareOccupancy", "Area",
            "Fellow", "Commments", "Name", "Position",
            "Dept", "FTE", "CrossApp", "CrossPos", "CrossDept",
            "CrossFTE", "OtherOffice"};
    for (String col : offSpaceCols) {
        offSpaceColumns.add(col);
    }

    //mainPanel.setSize(1260, 630);
    //mainPanel.setLayout(null);

    JRadioButton coursesBtn = new JRadioButton("Courses");
    coursesBtn.setMnemonic(KeyEvent.VK_C);
    coursesBtn.setActionCommand("Course");
    coursesBtn.setSelected(true);
    coursesBtn.addActionListener(this);

    JRadioButton profsBtn = new JRadioButton("Professors");
    profsBtn.setMnemonic(KeyEvent.VK_P);
    profsBtn.setActionCommand("Professors");
    profsBtn.addActionListener(this);

    JRadioButton officeSpBtn = new JRadioButton("Office Spaces");
    officeSpBtn.setMnemonic(KeyEvent.VK_O);
    officeSpBtn.setActionCommand("Office Spaces");
    officeSpBtn.addActionListener(this);

    ButtonGroup tablesBtns = new ButtonGroup();
    tablesBtns.add(coursesBtn);
    tablesBtns.add(profsBtn);
    tablesBtns.add(officeSpBtn);

    JPanel tableRadioPanel = new JPanel(new GridLayout(0, 1));
    tableRadioPanel.add(coursesBtn);
    tableRadioPanel.add(profsBtn);
    tableRadioPanel.add(officeSpBtn);

    //table start
    DefaultTableModel coursesModel = new DefaultTableModel(courseColumns, 200);
    dataTable = new JTable(coursesModel);
    dataTable.setFillsViewportHeight(true);
    dataTable.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

    JScrollPane scrollPane = new JScrollPane(dataTable, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
            JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
    //scrollPane.setBounds(160, 0, 1016, 558);
    //table code end

    JPanel gridConstrain = new JPanel();
    gridConstrain.add(tableRadioPanel);
    mainPanel.add(gridConstrain, BorderLayout.LINE_START);
    mainPanel.add(scrollPane);

}

public JComponent getMainPanel() {
    return mainPanel;
}

public JTable getDataTable() {
    return dataTable;
}


/**
 * Returns the list of columns for the given table
 * @param identifier the name of the table
 * @return a Vector<String> of column names
 */
public Vector<String> getColumns(String identifier) {
    switch (identifier) {
    case "Courses":
        if (payrollActive) {
            return courseColumnsPay;
        } else {
            return courseColumns;
        }
    case "Professors":
        return profsColumns;
    case "Office Spaces":
        return offSpaceColumns;
    default:
        return null;
    }
}

public static void createAndShowGui() {
    test1 vicu = new test1();

    JFrame frame = new JFrame("Victoria University Database Application");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
    JLabel emptyLabel = new JLabel("Empty Label");
    emptyLabel.setFont(emptyLabel.getFont().deriveFont(80f));
    //emptyLabel.setPreferredSize(new Dimension(175, 100));
    frame.getContentPane().add(emptyLabel, BorderLayout.PAGE_START);
    frame.getContentPane().add(vicu.getMainPanel());
    frame.pack();
    frame.setVisible(true);

}

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGui();
        }
    });

}

@Override
public void actionPerformed(ActionEvent e) {
    System.out.println("Event: " + e);
    JRadioButton targetBtn = (JRadioButton) e.getSource();
    ((DefaultTableModel) dataTable.getModel()).
    setColumnIdentifiers(getColumns(targetBtn.getText()));
}
}