Cannot update JTable's values after data change using setValueAt

Question

I've done JTable for simple schedule with visits. It contains custom AbstractTableModel which shows three columns shown below.

The problem is that it is possible to initializate Table and to get desired look - but after data change there is no change in appearance of Table. Each button click takes data from database and sets fields in columns TYPE and STATE - depending on given hour and date of reservation.

What is more I'am able to insert new row at the end of table but cannot make visible existing value update. I already read few similar topics but nothing helps in my case. Thanks in advance for every suggestions.

[UPDATED] Working code illustrating the problem:

import java.awt.EventQueue;
import java.util.Vector;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;

import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class ModelTest {

    private JFrame frame;
    private JTable tablePendingVisits;
    private PendingVisitModel pendingVisitModel;
    private JScrollPane scrollPanePendingVisits;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    ModelTest window = new ModelTest();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public ModelTest() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 407);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        JButton btnChangeValue = new JButton("Change value at 9:00");
        btnChangeValue.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                refreshTableModel();
            }
        });
        btnChangeValue.setBounds(63, 308, 305, 23);
        frame.getContentPane().add(btnChangeValue);

        tablePendingVisits = new JTable();
        scrollPanePendingVisits = new JScrollPane();
        pendingVisitModel = new PendingVisitModel();

        tablePendingVisits.setModel(pendingVisitModel);
        scrollPanePendingVisits.setBounds(63, 36, 305, 246);
        scrollPanePendingVisits.setViewportView(tablePendingVisits);

        frame.getContentPane().add(scrollPanePendingVisits);
    }

    public void refreshTableModel(){
        String[] sampleString = {"9:00", "Bobby", "Tables"};

        // search for row with 9:00 and replace values in given columns
        for (int i = 0; i < pendingVisitModel.getRowCount(); i++) {

            if( sampleString[0].equals(pendingVisitModel.getValueAt(i, 0)) ) {   // Change row values when both hours are equal 
                pendingVisitModel.setValueAt(sampleString[1], i, 1);             // Change at type column
                pendingVisitModel.setValueAt(sampleString[2], i, 2);             // Change at status column      
            }
        }
    }
}

// Custom TableModel
class PendingVisitModel extends AbstractTableModel {

    private static final long serialVersionUID = 1L;

    private String[] columnNames = {"HOUR", "TYPE", "STATE"};
    private Vector<String[]> data = new Vector<String[]>();

    public PendingVisitModel() {

        for(int i = 8; i<15; i++) {
            data.add(new String[]{i+":00", "-", "Free"} );
            data.add(new String[]{i+":15", "-", "Free"} );
            data.add(new String[]{i+":30", "-", "Free"} );
            data.add(new String[]{i+":45", "-", "Free"} );
        }
    }

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

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

    public String getColumnName(int col) {
        return columnNames[col];
    }

    public String getValueAt(int row, int col) {
        String[] temp = data.get(row);
        if(temp.length > 0 && col < 3)
            return temp[col];
        else
            return null;
    }

    public void setValueAt(String[] value, int row, int col) {
        String[] temp = data.get(row);
        temp[col] = value[col];

        data.set(row, temp);
        fireTableRowsUpdated(row, row);
    }

    public void insertRow(String[] value) {
        data.add(value);
        fireTableRowsInserted(data.size(), data.size());
    }

    public void clearRows(){
        data.clear();
        fireTableDataChanged();
    }

    public void removeAllEntry(){
        data.clear();
        fireTableDataChanged();
    }

    public boolean isCellEditable(int row, int col) {
        return false;
    }

    @Override
    public Class<String> getColumnClass(int colNum) {
        return String.class;
    }
}

Answer 1

PendingVisitModel pendingVisitModel = new PendingVisitModel();

It looks to me like the pendingVisitModel is defined as a local variable. This is the model you add to the table.

The refreshTableModel() method is referencing a pendingVisitModelvariable, but I would guess this is an instance variable that is NOT used by the table.

Get rid of local instance of your pendingVisitModel.

fireTableDataChanged();

Also don't keep using firTableDataChanged in all your TableModel methods. The API provides other methods that are more appropriate for different events.

Edit:

public void setValueAt(String[] value, int row, int col) {

You did not override the setValueAt(...) method. The value parameter is an Object not a String array.

Whenever you override a method of a class you should use the @Override annotation before the method. This way the compiler will give you an error if you override a method incorrectly (saving hours of frustration...).

@Override
public void setValueAt(Object value, int row, int col) {