Chapter 18. Tables

18.1 JTable

18.1.1 JTable

class javax.swing.JTable

18.1.2 The TableModel interface

abstract interface javax.swing.table.TableModel

18.1.3 AbstractTableModel

abstract class javax.swing.table.AbstractTableModel

18.1.4 DefaultTableModel

class javax.swing.tableDefaultTableModel

18.1.5 TableColumn

class javax.swing.table.TableColumn

TableColumn also maintains an isResizable property, specifying whether or not its width can be changed by the user (this does not apply to programmatic calls to setWidth()). (We will discuss resizing in more detail below).

An interesting and rarely used property maintained by TableColumn, resizedPostingDisabledCount, is used to enable/disable the posting of PropertyChangeEvents when a TableColumn’s width changes. This is an int value that is incremented on each call to disableResizedPosting(), and decremented on each call to enableResizedPosting(). Events will only be fired if this value is less than or equal to 0. The logic behind this is that if two separate sources both dis! able resize event posting, then two calls should be required to re-enable it.

TableColumn fires PropertyChangeEvents when any of the width, cellRenderer, headerRenderer, or headerValue bound properties change. Thus we can add and remove PropertyChangeListeners to be notified of these changes. The corresponding property names are COLUMN_WIDTH_PROPERTY, COLUMN_RENDERER_PROPERTY, HEADER_RENDERER_PROPERTY, and HEADER_VALUE_PROPERTY.

This model is designed to maintain a JTable’s TableColumns, and provides control over column selections and margin size. TableColumnModel controls how JTable displays its TableModel data. The addColumn() method should append a given TableColumn to the end of the structure used to maintain them (usually a Vector), rem! oveColumn() should remove a given TableColumn, and moveColumn() should change the location of a given TableColumn within that structure.

Unlike the location of a column in TableModel implementations, the index of a TableColumn in a TableColumnModel’s storage structure directly corresponds to its position in the JTable GUI. Note that the moveColumn() method is called whenever the user drags a column to a new position.

The getColumnCount() method should return the number of TableColumns currently maintained, getColumns() should return an Enumeration of all contained TableColumns, and getColumn() returns the TableColumn at the given index. The getColumnIndex() method should return the index of the TableColumn whose identifier property is equal to (using Object’s equals() method) the given Object. getColumnIndexAtX() should return the index of the TableColumn at the given x-corrdinate in table-space (if getColumnIndexAtX() is passed a coordinate that maps to the margin space between adjacent columns, or any x-coordinate that does not correspond to a table column, it will return -1). setColumnMargin() and get! ColumnMargin() should al! lo! w assignment and retrieval of an int value for use as the margin space on each side of each table column. The getTotalColumnWidth() should return the sum of the current width of all TableColumns including all margin space.

TableColumnModel declares methods for controlling the selection of its TableColumns, and allows assignment and retrieval of a ListSelectionModel implementation used to store information about the current column selection with the methods setSelectionModel() and getSelectionModel(). The setColumnSelectionAllowed() method is intended to turn on/off column selection capabilities, and getColumnSelectionAllowed() should return a boo! lean specifying whether slection is currently allowed or not. For convenience, JTable’s setColumnSelectionAllowed() method delegates its traffic to the method of the same signature in this interface.

TableColumnModel also declares support for TableColumnModelListeners (see below). TableColumnModel implementations are expected to fire a TableColumnModelEvent whenever a TableColumn is added, removed, or moved, a ChangeEvent whenever margin size is changed, and a ListSelectionEvent whenever a change in column selection occurs.

This class is the concrete default implementation of the TableColumnModel interface used by JTable when none is specifically assigned or provided at construction time. All TableColumnModel methods are implemented as expected (see above), and the following protected methods are provided to fire events: fireColumnAdded(), fireColumnRemoved(), fireColumnMoved(), fireColumnSelectionChanged(), and fireColumnMarginChanged(). A valueChanged() method is provided to listen for column selection changes and fire a ListSelectionEvent when necessary. And a propertyChanged() method is used to update the totalColumnWidth property when the width of a contained TableColumn changes.

This interface describes the renderer used to display cell data in a TableColumn. Each TableColumn has an associated TableCellRender which can be assigned/retrieved with the setCellRenderer()/getCellRenderer() methods. The getTableCellRendererComponent() method is the only method declared by this interface, and is expected to return a Component that will be used to actually render a cell. It takes the following parameters! :

We are expected to customize or vary the returned component based on the given parameters. For instance, given a value that is an instance of Color, we might return a special JLabel subclass that paints a rectangle in the given color. This method can be used to return different renderer components on a column, row, or cell-specific basis, and is similar to JTree’s TreeCellRenderer getTreeCellRendererComponent() method. As with JTree and JList, the renderer component returned acts as a "rubber stamp"^API used strictly for display purposes.

When JTable’s UI delegate repaints a certain region of a table it must query that table to determine the renderer to use for each cell that it needs to repaint. This is accomplished through JTable’s getCellRenderer() method which takes row and column parameters, and returns the component returned by the getTableCellRendererComponent() method of the TableCellRenderer assigned to the appropriate TableColumn. If there is no specific renderer assigned to that TableColumn (recall that this is the case by default), the TableModel’s getColumnClass() method is used to recursively determine an appropriate renderer for the given data type. If there is no specific class-based renderer specified for a given class, getColumnClass() searches for one corresponding to the super-class. This process will, in the most generic case, stop at Object, for which a DefaultTabelCellRenderer is used (see below).

A DefaultTreeCellRenderer is also used if the class is of type Number (subclasses are BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, and Short) or Icon. If the type ! happens to be a Boolean, a JCheckBox is used. We can specify additional class-based renderers with JTable’s setDefaultRenderer() method. Remember that class-based renderers will only be used if no column-based renderer has been explicitly assigned to the TableColumn containing the given cell.

  myJTable.getSelectionModel().setSelectedMode(ListSelectionModel.XX_SELECTION);

  myJTable.getColumnModel().getSelectionModel().setSelectionMode(ListSelectionModel.XX_SELECTION);

If these same cells are selected when cell selection is disabled and row and column selection are enabled, all cells in rows 1 and 3, and all cells in columns 5 and 6 will be considered selected. If they are selected with cell selection and only row selection enabled, all cells in rows 1 and 3 will be considered selected. Similarly, if these two cells are selected with cell selection and only column selection enabled, all cells in columns 5 and 6 will be considered selected. If cell selection is not enabled, and row and/or column selection is enabled, a cell will be considered selected if either a column or row containing it is selected.

  myJTable.addMouseListener(new MouseAdapter() {
    public void mouseClicked(MouseEvent e) {
      // get most recently selected row index
      int row = getSelectedRow();
      // get most recently selected column index
      int column = getSelectedColumn();
      if (row == -1 || column == -1)
        return; // can’t determine selected cell
      else
        // do something cell-specific
    }
  });

  myJTable.addMouseListener(new MouseAdapter() {
    public void mouseClicked(MouseEvent e) {
      if (e.getClickCount() == 2) {
        Point origin = e.getPoint();
        int row = myJTable.rowAtPoint(origin);
        int column = myJTable.columnAtPoint(origin);
        if (row == -1 || column == -1)
          return; // no cell found
        else
          // do something cell-specific 
      }
    }
  });

Stocks and stock trading is characterized by many attributes. The following are selected for display in our example:

Each stock attribute represents a column in our table, and each row represents a specific company’s stock information.

<<file figure18-1.gif>>

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.*;

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

public class StocksTable extends JFrame 
{
  protected JTable m_table;
  protected StockTableData m_data;
  protected JLabel m_title;

  public StocksTable() {
    super("Stocks Table");
    setSize(600, 300);

    m_data = new StockTableData();

    m_title = new JLabel(m_data.getTitle(), 
      new ImageIcon("money.gif"), SwingConstants.LEFT);
    m_title.setFont(new Font("TimesRoman",Font.BOLD,24));
    m_title.setForeground(Color.black);
    getContentPane().add(m_title, BorderLayout.NORTH);

    m_table = new JTable();
    m_table.setAutoCreateColumnsFromModel(false);
    m_table.setModel(m_data); 
        
    for (int k = 0; k < StockTableData.m_columns.length; k++) {
      DefaultTableCellRenderer renderer = new 
        DefaultTableCellRenderer();
      renderer.setHorizontalAlignment(
        StockTableData.m_columns[k].m_alignment);
      TableColumn column = new TableColumn(k, 
      StockTableData.m_columns[k].m_width, renderer, null);
      m_table.addColumn(column);   
    }

    JTableHeader header = m_table.getTableHeader();
    header.setUpdateTableInRealTime(false);

    JScrollPane ps = new JScrollPane();
    ps.getViewport().add(m_table);
    getContentPane().add(ps, BorderLayout.CENTER);

    WindowListener wndCloser = new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    };
    addWindowListener(wndCloser);
    setVisible(true);
  }

  public static void main(String argv[]) {
    new StocksTable();
  }
}

class StockData
{
  public String  m_symbol;
  public String  m_name;
  public Double  m_last;
  public Double  m_open;
  public Double  m_change;
  public Double  m_changePr;
  public Long    m_volume;

  public StockData(String symbol, String name, double last, 
   double open, double change, double changePr, long volume) {
    m_symbol = symbol;
    m_name = name;
    m_last = new Double(last);
    m_open = new Double(open);
    m_change = new Double(change);
    m_changePr = new Double(changePr);
    m_volume = new Long(volume);
  }
}

class ColumnData
{
  public String  m_title;
  public int     m_width;
  public int     m_alignment;

  public ColumnData(String title, int width, int alignment) {
    m_title = title;
    m_width = width;
    m_alignment = alignment;
  }
}

class StockTableData extends AbstractTableModel 
{
  static final public ColumnData m_columns[] = {
    new ColumnData( "Symbol", 100, JLabel.LEFT ),
    new ColumnData( "Name", 160, JLabel.LEFT ),
    new ColumnData( "Last", 100, JLabel.RIGHT ),
    new ColumnData( "Open", 100, JLabel.RIGHT ),
    new ColumnData( "Change", 100, JLabel.RIGHT ),
    new ColumnData( "Change %", 100, JLabel.RIGHT ),
    new ColumnData( "Volume", 100, JLabel.RIGHT )
  };

  protected SimpleDateFormat m_frm;
  protected Vector m_vector;
  protected Date   m_date;

  public StockTableData() {
    m_frm = new SimpleDateFormat("MM/dd/yyyy");
    m_vector = new Vector();
    setDefaultData();
  }

  public void setDefaultData() {
    try { 
      m_date = m_frm.parse("4/6/1999"); 
    }
    catch (java.text.ParseException ex) { 
      m_date = null; 
    }

    m_vector.removeAllElements();
    m_vector.addElement(new StockData("ORCL", "Oracle Corp.", 
      23.6875, 25.375, -1.6875, -6.42, 24976600));
    m_vector.addElement(new StockData("EGGS", "Egghead.com", 
      17.25, 17.4375, -0.1875, -1.43, 2146400));
    m_vector.addElement(new StockData("T", "AT&T", 
      65.1875, 66, -0.8125, -0.10, 554000));
    m_vector.addElement(new StockData("LU", "Lucent Technology", 
      64.625, 59.9375, 4.6875, 9.65, 29856300));
    m_vector.addElement(new StockData("FON", "Sprint", 
      104.5625, 106.375, -1.8125, -1.82, 1135100));
    m_vector.addElement(new StockData("ENML", "Enamelon Inc.", 
      4.875, 5, -0.125, 0, 35900)); 
    m_vector.addElement(new StockData("CPQ", "Compaq Computers", 
      30.875, 31.25, -0.375, -2.18, 11853900));
    m_vector.addElement(new StockData("MSFT", "Microsoft Corp.", 
      94.0625, 95.1875, -1.125, -0.92, 19836900));
    m_vector.addElement(new StockData("DELL", "Dell Computers", 
      46.1875, 44.5, 1.6875, 6.24, 47310000));
    m_vector.addElement(new StockData("SUNW", "Sun Microsystems", 
      140.625, 130.9375, 10, 10.625, 17734600));
    m_vector.addElement(new StockData("IBM", "Intl. Bus. Machines", 
      183, 183.125, -0.125, -0.51, 4371400));
    m_vector.addElement(new StockData("HWP", "Hewlett-Packard", 
      70, 71.0625, -1.4375, -2.01, 2410700));
    m_vector.addElement(new StockData("UIS", "Unisys Corp.", 
      28.25, 29, -0.75, -2.59, 2576200));
    m_vector.addElement(new StockData("SNE", "Sony Corp.", 
      96.1875, 95.625, 1.125, 1.18, 330600));
    m_vector.addElement(new StockData("NOVL", "Novell Inc.", 
      24.0625, 24.375, -0.3125, -3.02, 6047900));
    m_vector.addElement(new StockData("HIT", "Hitachi, Ltd.", 
      78.5, 77.625, 0.875, 1.12, 49400));
  }

  public int getRowCount() {
    return m_vector==null ? 0 : m_vector.size(); 
  }

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

  public String getColumnName(int column) { 
    return m_columns[column].m_title; 
  }
 
  public boolean isCellEditable(int nRow, int nCol) {
    return false;
  }

  public Object getValueAt(int nRow, int nCol) {
    if (nRow < 0 || nRow>=getRowCount())
      return "";
    StockData row = (StockData)m_vector.elementAt(nRow);
    switch (nCol) {
      case 0: return row.m_symbol;
      case 1: return row.m_name;
      case 2: return row.m_last;
      case 3: return row.m_open;
      case 4: return row.m_change;
      case 5: return row.m_changePr;
      case 6: return row.m_volume;
    }
    return "";
  }

  public String getTitle() {
    if (m_date==null)
      return "Stock Quotes";
    return "Stock Quotes at "+m_frm.format(m_date);
  }
}

As we will see below, the static array m_columns of the StockTableData class describes all columns of our table. It is used here to create each TableColumn instance and set their text alignment and width.

Method setHorizontalAlignment() (inherited by DefaultTableCellRenderer from JLabel) is used to set the proper alignment for each TableColumn’s cell renderer. The TableColumn constructor takes a column index, width, and renderer as parameters. Note that TableCellEditor is set to null since we don’t want to allow editing of stock data. Finally, columns are added to the table’s TableColumnM! odel (which JTable created by default because we didn’t specify one) with the addColumn() method.

In the next step, an instance of JTableHeader is created for this table, and the updateTableInRealTime property is set to false (this is done to demonstrate the effect this has on column dragging -- only a column’s table header is displayed during a drag).

Lastly a JScrollPane instance is used to provide scrolling capabilities, and our table is added to its JViewport. This JScrollPane is then added to the center of our frame’s content pane.

Note that all numerical data are encapsulated in Object-derived classes. This design decision simplifies data exchange with the table (as we will see below). The only constructor provided assigns each of these variables from the data passed as parameters.

This class encapsulates data describing the visual characteristics of a single TableColumn of our table. The instance variables defined in this class have the following meaning:

This class extends AbstractTableModel to serve as the data model for our table. Recall that AbstractTableModel is an abstract class, and three methods must be implemented to instantiate it:

By design, this class manages all information about our table, including the title and column data. A static array of ColumnData, m_columns, is provided to hold information about our table’s columns (it is used in the StocksTable constructor, see above). Three instance variables have the following meaning:

The only constructor of the StockTableData class initializes two of these variables and calls the setDefaultData() method to assign the pre-defined default data to m_date and m_vector (in a later example we’ll see how to use JDBC to retrieve data from a database rather than using hard-coded data as we do here).

<<file figure18-2.gif>>

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.*;

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

public class StocksTable extends JFrame 
{
  // Unchanged code from section 18.2

  public StocksTable() {
    // Unchanged code from section 18.2
        
    for (int k = 0; k < StockTableData.m_columns.length; k++) {
      DefaultTableCellRenderer renderer = new 
        ColoredTableCellRenderer();
      renderer.setHorizontalAlignment(
        StockTableData.m_columns[k].m_alignment);
      TableColumn column = new TableColumn(k, 
        StockTableData.m_columns[k].m_width, renderer, null);
      m_table.addColumn(column);   
    }

    // Unchanged code from section 18.2
  }

  public static void main(String argv[]) {
    new StocksTable();
  }
}

class ColoredTableCellRenderer extends DefaultTableCellRenderer
{
  public void setValue(Object value) {
    if (value instanceof ColorData) {
      ColorData cvalue = (ColorData)value;
      setForeground(cvalue.m_color);
      setText(cvalue.m_data.toString());
    }
    else if (value instanceof IconData) {
      IconData ivalue = (IconData)value;
      setIcon(ivalue.m_icon);
      setText(ivalue.m_data.toString());
    }
    else
      super.setValue(value);
  }
}

class ColorData
{
  public Color  m_color;
  public Object m_data;
  public static Color GREEN = new Color(0, 128, 0);
  public static Color RED = Color.red;

  public ColorData(Color color, Object data) {
    m_color = color;
    m_data  = data;
  }
    
  public ColorData(Double data) {
    m_color = data.doubleValue() >= 0 ? GREEN : RED;
    m_data  = data;
  }
    
  public String toString() {
    return m_data.toString();
  }
}

class IconData
{
  public ImageIcon  m_icon;
  public Object m_data;

  public IconData(ImageIcon icon, Object data) {
    m_icon = icon;
    m_data = data;
  }
    
  public String toString() {
    return m_data.toString();
  }
}

class StockData
{
  public static ImageIcon ICON_UP = new ImageIcon("ArrUp.gif");
  public static ImageIcon ICON_DOWN = new ImageIcon("ArrDown.gif");
  public static ImageIcon ICON_BLANK = new ImageIcon("blank.gif");

  public IconData  m_symbol;
  public String  m_name;
  public Double  m_last;
  public Double  m_open;
  public ColorData  m_change;
  public ColorData  m_changePr;
  public Long    m_volume;

  public StockData(String symbol, String name, double last, 
   double open, double change, double changePr, long volume) {
    m_symbol = new IconData(getIcon(change), symbol);
    m_name = name;
    m_last = new Double(last);
    m_open = new Double(open);
    m_change = new ColorData(new Double(change));
    m_changePr = new ColorData(new Double(changePr));
    m_volume = new Long(volume);
  }

  public static ImageIcon getIcon(double change) {
    return (change>0 ? ICON_UP : (change<0 ? ICON_DOWN : 
      ICON_BLANK));
  }
}

This class is used to bind ImageIcon m_icon to a data object of any nature, m_data. Its only constructor takes ImageIcon and Object parameters. The toString() method simply calls the toString() method of the data object.

This class has been enhanced from its previous version to to provide images and new variable data types. We’ve prepared three static ImageIcon instances holding images: arrow up, arrow down, and a blank (all transparent) image. The static getIcon() method returns one of these images depending on the sign of the given double parameter. We’ve also changed three instance variables to bind data with the color and image attributes according to the following table:

m_symbol IconData String Stock’s symbol (NYSE or NASDAQ)

m_change ColorData Double Absolute change in price

m_changePr ColorData Double Percent change in price

The corresponding changes are also required in the StockData constructor.

Figure 18.2 shows StocksTable with custom rendering in action. Note the correct usage of color and icons, which considerably enhances the visualization of our data.

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.*;

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

// Unchanged code from section 18.3

class Fraction
{
  public int m_whole;
  public int m_nom;
  public int m_den;

  public Fraction(double value) {
    int sign = value <0 ? -1 : 1;
    value = Math.abs(value);
    m_whole = (int)value;
    m_den = 32;
    m_nom = (int)((value-m_whole)*m_den);
    while (m_nom!=0 && m_nom%2==0) {
      m_nom /= 2;
      m_den /= 2;
    }
    if (m_whole==0)
      m_nom *= sign;
    else
      m_whole *= sign;
  }

  public double doubleValue() {
    return (double)m_whole + (double)m_nom/m_den;
  }

  public String toString() {
    if (m_nom==0)
      return ""+m_whole;
    else if (m_whole==0)
      return ""+m_nom+"/"+m_den;
    else
      return ""+m_whole+" "+m_nom+"/"+m_den;
  }
}

class SmartLong
{
  protected static NumberFormat FORMAT;

  static {
    FORMAT = NumberFormat.getInstance();
    FORMAT.setGroupingUsed(true);
  }

  public long m_value;

  public SmartLong(long value) { m_value = value; }

  public long longValue() { return m_value; }

  public String toString() { return FORMAT.format(m_value); }
}

class ColorData
{
  public ColorData(Fraction data) {
    m_color = data.doubleValue() >= 0 ? GREEN : RED;
    m_data  = data;
  }

  // Unchanged code from section 18.3
}

class StockData
{
  public static ImageIcon ICON_UP = new ImageIcon("ArrUp.gif");
  public static ImageIcon ICON_DOWN = new ImageIcon("ArrDown.gif");
  public static ImageIcon ICON_BLANK = new ImageIcon("blank.gif");

  public IconData  m_symbol;
  public String  m_name;
  public Fraction  m_last;
  public Fraction  m_open;
  public ColorData  m_change;
  public ColorData  m_changePr;
  public SmartLong  m_volume;

  public StockData(String symbol, String name, double last, 
   double open, double change, double changePr, long volume) {
    m_symbol = new IconData(getIcon(change), symbol);
    m_name = name;
    m_last = new Fraction(last);
    m_open = new Fraction(open);
    m_change = new ColorData(new Fraction(change));
    m_changePr = new ColorData(new Double(changePr));
    m_volume = new SmartLong(volume);
}

Method doubleValue() performs the opposite task: it converts the fraction into a double value. Method toString() forms a String representation of the fraction.

This class encapsulates long values. The only constructor takes a long as parameter and stores it in the m_value instance variable. The real purpose of creating this class is the overridden toString() method, which inserts commas separating thousands, millions, etc. places. For this purpose we use the java.text.NumberFormat class. An instance of this class is created as a static variable, and formatting values using NumberFormat’s format() method couldn’t be easier.

This class requires a new constructor to cooperate with the new Fraction data type. This third constructor takes a Fraction instance as parameter and uses its color attribute in the same way it did previously: green for positive values, and red for negative values.

m_symbol IconData String Stock symbol (NYSE or NASDAQ)

The StockData constructor is modified accordingly. Meanwhile the parameters in the StockData constructor have not changed, so there is no need to make any changes to the data model class using StockData.

Figure 18.3 shows StocksTable in action with number formatting. Presented this way, our data looks much more familiar to most of those who follow the stock trade on a regular basis.

To do this we add a mouse listener to the table header to capture mouse clicks and trigger a table sort. Fortunately sorting can be accomplished fairly easily using the new Collections functionality in Java 2.

We use the java.util.Collections.sort(List lst, Comparator c) method to sort any collection implementing the java.util.List interface based on a given Comparator. A Comparator implementation requires two methods:

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.*;

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

public class StocksTable extends JFrame 
{
  // Unchanged code from section 18.4

  public StocksTable() {
    // Unchanged code from section 18.4

    JTableHeader header = m_table.getTableHeader();
    header.setUpdateTableInRealTime(true);
    header.addMouseListener(m_data.new ColumnListener(m_table));
    header.setReorderingAllowed(true);
    
    // Unchanged code from section 18.4
  }

  public static void main(String argv[]) {
    new StocksTable();
  }
}

// Unchanged code from section 18.4

class StockTableData extends AbstractTableModel
{
  // Unchanged code from section 18.2

  protected SimpleDateFormat m_frm;
  protected Vector m_vector;
  protected Date   m_date;

  protected int m_sortCol = 0;
  protected boolean m_sortAsc = true;

  public StockTableData() {
    m_frm = new SimpleDateFormat("MM/dd/yyyy");
    m_vector = new Vector();
    setDefaultData();
  }

  public void setDefaultData() {
    // Unchanged code from section 18.4

    Collections.sort(m_vector, new 
      StockComparator(m_sortCol, m_sortAsc));
  }

  // Unchanged code from section 18.4 

  public String getColumnName(int column) {
    String str = m_columns[column].m_title;
    if (column==m_sortCol)
      str += m_sortAsc ? " »" : " «";
    return str;
  }
 
  // Unchanged code from section 18.4

  class ColumnListener extends MouseAdapter
  {
    protected JTable m_table;

    public ColumnListener(JTable table) {
      m_table = table;
    }

    public void mouseClicked(MouseEvent e) {
      TableColumnModel colModel = m_table.getColumnModel();
      int columnModelIndex = colModel.getColumnIndexAtX(e.getX());
      int modelIndex = colModel.getColumn(columnModelIndex).getModelIndex();

      if (modelIndex < 0)
        return;
      if (m_sortCol==modelIndex)
        m_sortAsc = !m_sortAsc;
      else
        m_sortCol = modelIndex;

      for (int i=0; i < m_columns.length; i++) {
        TableColumn column = colModel.getColumn(i);
        column.setHeaderValue(getColumnName(column.getModelIndex()));    
      }
      m_table.getTableHeader().repaint();  

      Collections.sort(m_vector, new 
        StockComparator(modelIndex, m_sortAsc));
      m_table.tableChanged(
        new TableModelEvent(StockTableData.this)); 
      m_table.repaint();  
    }
  }
}

class StockComparator implements Comparator
{
  protected int     m_sortCol;
  protected boolean m_sortAsc;

  public StockComparator(int sortCol, boolean sortAsc) {
    m_sortCol = sortCol;
    m_sortAsc = sortAsc;
  }

  public int compare(Object o1, Object o2) {
    if(!(o1 instanceof StockData) || !(o2 instanceof StockData))
      return 0;
    StockData s1 = (StockData)o1;
    StockData s2 = (StockData)o2;
    int result = 0;
    double d1, d2;
    switch (m_sortCol) {
      case 0:    // symbol
        String str1 = (String)s1.m_symbol.m_data;
        String str2 = (String)s2.m_symbol.m_data;
        result = str1.compareTo(str2);
        break;
      case 1:    // name
        result = s1.m_name.compareTo(s2.m_name);
        break;
      case 2:    // last
        d1 = s1.m_last.doubleValue();
        d2 = s2.m_last.doubleValue();
        result = d1<d2 ? -1 : (d1>d2 ? 1 : 0);
        break;
      case 3:    // open
        d1 = s1.m_open.doubleValue();
        d2 = s2.m_open.doubleValue();
        result = d1<d2 ? -1 : (d1>d2 ? 1 : 0);
        break;
      case 4:    // change
        d1 = ((Fraction)s1.m_change.m_data).doubleValue();
        d2 = ((Fraction)s2.m_change.m_data).doubleValue();
        result = d1<d2 ? -1 : (d1>d2 ? 1 : 0);
        break;
      case 5:    // change %
        d1 = ((Double)s1.m_changePr.m_data).doubleValue();
        d2 = ((Double)s2.m_changePr.m_data).doubleValue();
        result = d1<d2 ? -1 : (d1>d2 ? 1 : 0);
        break;
      case 6:    // volume
        long l1 = s1.m_volume.longValue();
        long l2 = s2.m_volume.longValue();
        result = l1<l2 ? -1 : (l1>l2 ? 1 : 0);
        break;
    }

    if (!m_sortAsc)
      result = -result;
    return result;
  }

  public boolean equals(Object obj) {
    if (obj instanceof StockComparator) {
      StockComparator compObj = (StockComparator)obj;
      return (compObj.m_sortCol==m_sortCol) && 
        (compObj.m_sortAsc==m_sortAsc);
    }
    return false;
  }
}

In the StocksTable constructor we set the updateTableInRealTime property to show column contents while columns are dragged, and we add an instance of the ColumnListener class (see below) as a mouse listener to the table’s header.

Here we declare two new instance variables: int m_sortCol to hold the index of the current column chosen for sorting, and boolean m_sortAsc, which is true when sorting in ascending order, and false when sorting in descending order. These variables determine the initial sorting order. To be consistent we sort our table initially by calling the Collections.sort() method in our setDefaultData() method (which is called from the StockTableData constructor).

  public String getColumnName(int column) {
    String str = m_columns[column].m_title;
    if (column==m_sortCol)
      str += m_sortAsc ? " »" : " «";
    return str;
  }

Because this class interacts heavily with our table data, it is implemented as an inner class in StockTableData. ColumnListener takes a reference to a JTable in its constructor and stores that reference in its m_table instance variable.

The mouseClicked() method is invoked when the user clicks on a header. First it determines the index of the TableColumn clicked based on the coordinate of the click. If for any reason the returned index is negative (i.e. the column cannot be determined) the method cannot continue and we return. Otherwise, we check whether this index corresponds to the column which already has been selected for sorting. If so, we invert the m_sortCol flag to reverse the sorting order. If the index corresponds to newly selected column we store the new sorting index in the m_sortCol variable.

Two instance variables are defined:

Table SYMBOLS

name Text

Table DATA

date1 Date/Time

last Number

change Number

changeproc Number

open Number

volume Number

For this example we use the JDBC-ODBC bridge which is a standard part of JDK since the 1.1 release and links Java programs to Microsoft Access databases. If you are using another database engine, you can work with this example as well, but you must make sure that the structure of your tables is the same. Before running the example in a Windows environment we need to register a database in an ODBC Data Source Administrator which is accessible through the Control Panel (this is not a JDBC tutorial, so we’ll skip the details).

<<file figure18-5.gif>>

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.*;
import java.sql.*;

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

public class StocksTable extends JFrame
{
    protected JTable m_table;
    protected StockTableData m_data;
    protected JLabel m_title;

  public StocksTable() {
    // Unchanged code from section 18.4

    JMenuBar menuBar = createMenuBar();
      setJMenuBar(menuBar);

    // Unchanged code
  }

  protected JMenuBar createMenuBar() {
    JMenuBar menuBar = new JMenuBar();
        
    JMenu mFile = new JMenu("File");
    mFile.setMnemonic('f');

    JMenuItem mData = new JMenuItem("Retrieve Data...");
    mData.setMnemonic('r');
    ActionListener lstData = new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
        retrieveData(); 
      }
    };
    mData.addActionListener(lstData);
    mFile.add(mData);
    mFile.addSeparator();

    JMenuItem mExit = new JMenuItem("Exit");
    mExit.setMnemonic('x');
    ActionListener lstExit = new ActionListener() { 
      public void actionPerformed(ActionEvent e) {
        System.exit(0);
      }
    };
    mExit.addActionListener(lstExit);
    mFile.add(mExit);
    menuBar.add(mFile);

    return menuBar;
  }

  public void retrieveData() {
    SimpleDateFormat frm = new SimpleDateFormat("MM/dd/yyyy");
    String currentDate = frm.format(m_data.m_date);
    String result = (String)JOptionPane.showInputDialog(this, 
      "Please enter date in form mm/dd/yyyy:", "Input", 
      JOptionPane.INFORMATION_MESSAGE, null, null, 
      currentDate);
    if (result==null)
      return;

    java.util.Date date = null;
    try { 
      date = frm.parse(result); 
    }
    catch (java.text.ParseException ex) { 
      date = null; 
    }
        
    if (date == null) {
      JOptionPane.showMessageDialog(this, 
        result+" is not a valid date",
        "Warning", JOptionPane.WARNING_MESSAGE);
      return;
    }

    setCursor( Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR) );
    switch (m_data.retrieveData(date)) {
      case 0:    // Ok with data
        m_title.setText(m_data.getTitle());
        m_table.tableChanged(new TableModelEvent(m_data)); 
        m_table.repaint();
        break;
      case 1: // No data
        JOptionPane.showMessageDialog(this, 
          "No data found for "+result,
          "Warning", JOptionPane.WARNING_MESSAGE);
        break;
      case -1: // Error
        JOptionPane.showMessageDialog(this, 
          "Error retrieving data",
          "Warning", JOptionPane.WARNING_MESSAGE);
        break;
    }
    setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
  }

  public static void main(String argv[]) {
    new StocksTable();
  }
}

// Unchanged code from section 18.4

class StockTableData extends AbstractTableModel 
{
  static final public ColumnData m_columns[] = {
    // Unchanged code from section 18.2
  };

  protected SimpleDateFormat m_frm;
  protected Vector m_vector;
  protected java.util.Date m_date; // conflict with

  protected int m_sortCol = 0;
  protected boolean m_sortAsc = true;

  protected int m_result = 0;

  public StockTableData() {
    m_frm = new SimpleDateFormat("MM/dd/yyyy");
    m_vector = new Vector();
    setDefaultData();
  }

  // Unchanged code from section 18.4

  public int retrieveData(final java.util.Date date) {
    GregorianCalendar calendar = new GregorianCalendar();
    calendar.setTime(date);
    int month = calendar.get(Calendar.MONTH)+1;
    int day = calendar.get(Calendar.DAY_OF_MONTH);
    int year = calendar.get(Calendar.YEAR);

    final String query = "SELECT data.symbol, symbols.name, "+
      "data.last, data.open, data.change, data.changeproc, "+
      "data.volume FROM DATA INNER JOIN SYMBOLS "+
      "ON DATA.symbol = SYMBOLS.symbol WHERE "+
      "month(data.date1)="+month+" AND day(data.date1)="+day+
      " AND year(data.date1)="+year;

    Thread runner = new Thread() {
      public void run() {
        try {
          // Load the JDBC-ODBC bridge driver
          Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
          Connection conn = DriverManager.getConnection(
            "jdbc:odbc:Market", "admin", "");

          Statement stmt = conn.createStatement();
          ResultSet results = stmt.executeQuery(query);

          boolean hasData = false;
          while (results.next()) {
            if (!hasData) {
              m_vector.removeAllElements();
              hasData = true;
            }
            String  symbol = results.getString(1);
            String  name = results.getString(2);
            double  last = results.getDouble(3);
            double  open = results.getDouble(4);
            double  change = results.getDouble(5);
            double  changePr = results.getDouble(6);
            long volume = results.getLong(7);
            m_vector.addElement(new StockData(symbol, name, last, 
              open, change, changePr, volume));
          }
          results.close();
          stmt.close();
          conn.close();

          if (!hasData)    // We've got nothing
            m_result = 1;
        }
        catch (Exception e) {
          e.printStackTrace();
          System.err.println("Load data error: "+e.toString());
          m_result = -1;
        }
        m_date = date;
        Collections.sort(m_vector, 
          new StockComparator(m_sortCol, m_sortAsc));
        m_result = 0;
      }
    };
    runner.start();

    return m_result;
  }

  // Unchanged code from section 18.4
}

// Class StockComparator unchanged from section 18.4

<<file figure18-6.gif>>

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.*;
import java.sql.*;

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

public class StocksTable extends JFrame 
{
  // Unchanged code from section 18.5
  
  public StocksTable() {
    // Unchanged code from section 18.5
    header.setReorderingAllowed(true);

    m_table.getColumnModel().addColumnModelListener(
      m_data.new ColumnMovementListener());

    // Unchanged code from section 18.5
  }  

  protected JMenuBar createMenuBar() {
    // Unchanged code from section 18.5

    JMenu mView = new JMenu("View");
    mView.setMnemonic('v');
    TableColumnModel model = m_table.getColumnModel();
    for (int k = 0; k < StockTableData.m_columns.length; k++) {
      JCheckBoxMenuItem item = new JCheckBoxMenuItem(
        StockTableData.m_columns[k].m_title);
      item.setSelected(true);
      TableColumn column = model.getColumn(k);
      item.addActionListener(new ColumnKeeper(column, 
        StockTableData.m_columns[k]));
      mView.add(item);
    }
    menuBar.add(mView);

    return menuBar;
  }

  // Unchanged code from section 18.5

  class ColumnKeeper implements ActionListener
  {
    protected TableColumn m_column;
    protected ColumnData  m_colData;

    public ColumnKeeper(TableColumn column, ColumnData  colData) {
      m_column = column;
      m_colData = colData;
    }

    public void actionPerformed(ActionEvent e) {
      JCheckBoxMenuItem item = (JCheckBoxMenuItem)e.getSource();
      TableColumnModel model = m_table.getColumnModel();
      if (item.isSelected()) {
        model.addColumn(m_column);
      }
      else {
        model.removeColumn(m_column);
      }
      m_table.tableChanged(new TableModelEvent(m_data)); 
      m_table.repaint();
    }
  }

  public static void main(String argv[]) {
    new StocksTable();
  }
}

// Unchanged code from section 18.5

class StockTableData extends AbstractTableModel 
{
  // Unchanged code from section 18.5

  protected SimpleDateFormat m_frm;
  protected Vector m_vector;
  protected java.util.Date m_date;
  protected int m_columnsCount = m_columns.length;

  // Unchanged code from section 18.5 

  public int getColumnCount() { 
    return m_columnsCount;
  }

  // Unchanged code from section 18.5

  class ColumnListener extends MouseAdapter
  {
    // Unchanged code from section 18.4

    public void mouseClicked(MouseEvent e) {
      // Unchanged code from section 18.4

      for (int i=0; i < m_columnsCount; i++) {
        TableColumn column = colModel.getColumn(i);
        column.setHeaderValue(getColumnName(column.getModelIndex()));    
      }
      m_table.getTableHeader().repaint();  

      // Unchanged code from section 18.4
    }
  }

  class ColumnMovementListener implements TableColumnModelListener
  {
    public void columnAdded(TableColumnModelEvent e) {
      m_columnsCount++;
    }

    public void columnRemoved(TableColumnModelEvent e) {
      m_columnsCount--;
    }

    public void columnMarginChanged(ChangeEvent e) {}
    public void columnMoved(TableColumnModelEvent e) {}
    public void columnSelectionChanged(ListSelectionEvent e) {}
  }
  // Unchanged code from section 18.5
}

// Class StockComparator unchanged from section 18.4

Figure 18.7 shows the new "View" menu with an unchecked "Change %" menu item, and the corresponding column hidden. Reselecting this menu item will place the column back in the table at the end position. Verify that each menu item functions similarly.

The editing of data generally follows this scheme:

<<file figure18-7.gif>>

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.SimpleDateFormat;

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

public class ExpenseReport extends JFrame 
{
  protected JTable m_table;
  protected ExpenseReportData m_data;
  protected JLabel m_title;

  public ExpenseReport() {
    super("Expense Report");
    setSize(570, 200);

    m_data = new ExpenseReportData(this);

    m_table = new JTable();
    m_table.setAutoCreateColumnsFromModel(false);
    m_table.setModel(m_data); 
    m_table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        
    for (int k = 0; k < ExpenseReportData.m_columns.length; k++) {
      TableCellRenderer renderer;
      if (k==ExpenseReportData.COL_APPROVED)
        renderer = new CheckCellRenderer();
      else {
        DefaultTableCellRenderer textRenderer = 
          new DefaultTableCellRenderer();
        textRenderer.setHorizontalAlignment(
          ExpenseReportData.m_columns[k].m_alignment);
        renderer = textRenderer;
      }

      TableCellEditor editor;

      if (k==ExpenseReportData.COL_CATEGORY)
        editor = new DefaultCellEditor(new JComboBox(
          ExpenseReportData.CATEGORIES));
      else if (k==ExpenseReportData.COL_APPROVED)
        editor = new DefaultCellEditor(new JCheckBox());
      else
        editor = new DefaultCellEditor(new JTextField());

      TableColumn column = new TableColumn(k, 
        ExpenseReportData.m_columns[k].m_width, 
          renderer, editor);
        m_table.addColumn(column);   
    }

    JTableHeader header = m_table.getTableHeader();
    header.setUpdateTableInRealTime(false);

    JScrollPane ps = new JScrollPane();
    ps.setSize(550, 150);
    ps.getViewport().add(m_table);
    getContentPane().add(ps, BorderLayout.CENTER);

    JPanel p = new JPanel();
    p.setLayout(new BoxLayout(p, BoxLayout.X_AXIS));

    ImageIcon penny = new ImageIcon("penny.gif");
    m_title = new JLabel("Total: $", 
      penny, JButton.LEFT);
    m_title.setForeground(Color.black);
    m_title.setAlignmentY(0.5f);
    p.add(m_title);
    p.add(Box.createHorizontalGlue());

    JButton bt = new JButton("Insert before");
    bt.setMnemonic('b');
    bt.setAlignmentY(0.5f);
    ActionListener lst = new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
        int row = m_table.getSelectedRow();
        m_data.insert(row);
        m_table.tableChanged(new TableModelEvent(
          m_data, row, row, TableModelEvent.ALL_COLUMNS, 
          TableModelEvent.INSERT)); 
        m_table.repaint();
      }
    };
    bt.addActionListener(lst);
    p.add(bt);

    bt = new JButton("Insert after");
    bt.setMnemonic('a');
    bt.setAlignmentY(0.5f);
    lst = new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
        int row = m_table.getSelectedRow();
        m_data.insert(row+1);
        m_table.tableChanged(new TableModelEvent(
          m_data, row+1, row+1, TableModelEvent.ALL_COLUMNS,
          TableModelEvent.INSERT)); 
        m_table.repaint();
      }
    };
    bt.addActionListener(lst);
    p.add(bt);

    bt = new JButton("Delete row");
    bt.setMnemonic('d');
    bt.setAlignmentY(0.5f);
    lst = new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
        int row = m_table.getSelectedRow();
        if (m_data.delete(row)) {
          m_table.tableChanged(new TableModelEvent(
            m_data, row, row, TableModelEvent.ALL_COLUMNS,
            TableModelEvent.INSERT)); 
          m_table.repaint();
          calcTotal();
        }
      }
    };
    bt.addActionListener(lst);
    p.add(bt);
      
    getContentPane().add(p, BorderLayout.SOUTH);

    calcTotal();

    WindowListener wndCloser = new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    };
    addWindowListener(wndCloser);
    
    setVisible(true);
  }

  public void calcTotal() {
    double total = 0;
    for (int k=0; k < m_data.getRowCount(); k++) {
      Double amount = (Double)m_data.getValueAt(k, 
        ExpenseReportData.COL_AMOUNT);
      total += amount.doubleValue();
    }
    m_title.setText("Total: $"+total);
  }

  public static void main(String argv[]) {
    new ExpenseReport();
  }
}

class CheckCellRenderer extends JCheckBox implements TableCellRenderer
{
  protected static Border m_noFocusBorder;

  public CheckCellRenderer() {
    super();
    m_noFocusBorder = new EmptyBorder(1, 2, 1, 2);
    setOpaque(true);
    setBorder(m_noFocusBorder);
  }

  public Component getTableCellRendererComponent(JTable table,
   Object value, boolean isSelected, boolean hasFocus, 
   int row, int column) 
  {
    if (value instanceof Boolean) {
      Boolean b = (Boolean)value;
      setSelected(b.booleanValue());
    }

    setBackground(isSelected && !hasFocus ? 
      table.getSelectionBackground() : table.getBackground());
    setForeground(isSelected && !hasFocus ? 
      table.getSelectionForeground() : table.getForeground());
        
    setFont(table.getFont());
    setBorder(hasFocus ? UIManager.getBorder(
      "Table.focusCellHighlightBorder") : m_noFocusBorder);

    return this;
  }
}

class ExpenseData
{
  public Date    m_date;
  public Double  m_amount;
  public Integer m_category;
  public Boolean m_approved;
  public String  m_description;

  public ExpenseData() {
    m_date = new Date();
    m_amount = new Double(0);
    m_category = new Integer(1);
    m_approved = new Boolean(false);
    m_description = "";
  }

  public ExpenseData(Date date, double amount, int category, 
   boolean approved, String description) 
  {
    m_date = date;
    m_amount = new Double(amount);
    m_category = new Integer(category);
    m_approved = new Boolean(approved);
    m_description = description;
  }
}

class ColumnData
{
  public String  m_title;
  int m_width;
  int m_alignment;

  public ColumnData(String title, int width, int alignment) {
    m_title = title;
    m_width = width;
    m_alignment = alignment;
  }
}

class ExpenseReportData extends AbstractTableModel 
{
  public static final ColumnData m_columns[] = {
    new ColumnData( "Date", 80, JLabel.LEFT ),
    new ColumnData( "Amount", 80, JLabel.RIGHT ),
    new ColumnData( "Category", 130, JLabel.LEFT ),
    new ColumnData( "Approved", 80, JLabel.LEFT ),
    new ColumnData( "Description", 180, JLabel.LEFT )
  };

  public static final int COL_DATE = 0;
  public static final int COL_AMOUNT = 1;
  public static final int COL_CATEGORY = 2;
  public static final int COL_APPROVED = 3;
  public static final int COL_DESCR = 4;

  public static final String[] CATEGORIES = {
    "Fares", "Logging", "Business meals", "Others"
  };

  protected ExpenseReport m_parent;
  protected SimpleDateFormat m_frm;
  protected Vector m_vector;

  public ExpenseReportData(ExpenseReport parent) {
    m_parent = parent;
    m_frm = new SimpleDateFormat("MM/dd/yy");
    m_vector = new Vector();
    setDefaultData();
  }

  public void setDefaultData() {
    m_vector.removeAllElements();
    try {
      m_vector.addElement(new ExpenseData(
      m_frm.parse("04/06/99"), 200, 0, true, 
        "Airline tickets"));
      m_vector.addElement(new ExpenseData(
        m_frm.parse("04/06/99"), 50,  2, false, 
        "Lunch with client"));
      m_vector.addElement(new ExpenseData(
        m_frm.parse("04/06/99"), 120, 1, true, 
        "Hotel"));
    }
    catch (java.text.ParseException ex) {}
  }

  public int getRowCount() {
    return m_vector==null ? 0 : m_vector.size(); 
  }

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

  public String getColumnName(int column) { 
    return m_columns[column].m_title; 
  }
 
  public boolean isCellEditable(int nRow, int nCol) {
    return true;
  }

  public Object getValueAt(int nRow, int nCol) {
    if (nRow < 0 || nRow>=getRowCount())
      return "";
    ExpenseData row = (ExpenseData)m_vector.elementAt(nRow);
    switch (nCol) {
      case COL_DATE: return m_frm.format(row.m_date);
      case COL_AMOUNT: return row.m_amount;
      case COL_CATEGORY: return CATEGORIES[row.m_category.intValue()];
      case COL_APPROVED: return row.m_approved;
      case COL_DESCR: return row.m_description;
    }
    return "";
  }

  public void setValueAt(Object value, int nRow, int nCol) {
    if (nRow < 0 || nRow >= getRowCount())
      return;
    ExpenseData row = (ExpenseData)m_vector.elementAt(nRow);
    String svalue = value.toString();

    switch (nCol) {
      case COL_DATE: 
        Date  date = null;
        try { 
          date = m_frm.parse(svalue); 
        }
        catch (java.text.ParseException ex) { 
          date = null; 
        }
        if (date == null) {
          JOptionPane.showMessageDialog(null, 
            svalue+" is not a valid date",
            "Warning", JOptionPane.WARNING_MESSAGE);
          return;
        }
        row.m_date = date; 
        break;
      case COL_AMOUNT:
        try { 
          row.m_amount = new Double(svalue); 
        }
        catch (NumberFormatException e) { break; }
        m_parent.calcTotal();
        break;
      case COL_CATEGORY:
        for (int k=0; k < CATEGORIES.length; k++)
          if (svalue.equals(CATEGORIES[k])) {
            row.m_category = new Integer(k);
            break;
          }
        break;
      case COL_APPROVED:
        row.m_approved = (Boolean)value; 
        break;
      case COL_DESCR:
        row.m_description = svalue; 
        break;
    }
  }

  public void insert(int row) {
    if (row < 0)
      row = 0;
    if (row > m_vector.size())
      row = m_vector.size();
    m_vector.insertElementAt(new ExpenseData(), row);
  }

  public boolean delete(int row) {
    if (row < 0 || row >= m_vector.size())
      return false;
    m_vector.remove(row);
      return true;
  }
}

Try editing different columns and note how the corresponding cell editors work. Experiment with adding and removing table rows and note how the total amount is updated each time the "Amount" column is updated. Figure 18.8 shows ExpenseReport with a combo box opened to change a cell’s value.

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.beans.*;
import java.lang.reflect.*;
import java.util.*;

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

import dl.*;

public class BeanContainer extends JFrame implements FocusListener
{
  protected Hashtable m_editors = new Hashtable();

  // Unchanged code from section 4.7

  protected JMenuBar createMenuBar() {
    // Unchanged code from section 4.7

    JMenu mEdit = new JMenu("Edit");
    mItem = new JMenuItem("Delete");
    lst = new ActionListener() { 
      public void actionPerformed(ActionEvent e) {
        if (m_activeBean == null)
          return;
        Object obj = m_editors.get(m_activeBean);
        if (obj != null) {
          BeanEditor editor = (BeanEditor)obj;
          editor.dispose();
          m_editors.remove(m_activeBean);
        }
        getContentPane().remove(m_activeBean);
        m_activeBean = null;
        validate();
        repaint();
      }
    };
    mItem.addActionListener(lst);
    mEdit.add(mItem);

    mItem = new JMenuItem("Properties...");
    lst = new ActionListener() { 
      public void actionPerformed(ActionEvent e) {
        if (m_activeBean == null)
          return;
        Object obj = m_editors.get(m_activeBean);
        if (obj != null) {
          BeanEditor editor = (BeanEditor)obj;
          editor.setVisible(true);
          editor.toFront();
        }
        else {
          BeanEditor editor = new BeanEditor(m_activeBean);
          m_editors.put(m_activeBean, editor);
        }
      }
    };
    mItem.addActionListener(lst);
    mEdit.add(mItem);
    menuBar.add(mEdit);

    // Unchanged code from section 4.7

    return menuBar;
  }

  // Unchanged code from section 4.7
}

class BeanEditor extends JFrame implements PropertyChangeListener
{
  protected Component m_bean;
  protected JTable m_table;
  protected PropertyTableData m_data;
    
  public BeanEditor(Component bean) {
    m_bean = bean;
    m_bean.addPropertyChangeListener(this);

    Point pt = m_bean.getLocationOnScreen();
    setBounds(pt.x+50, pt.y+10, 400, 300);
    getContentPane().setLayout(new BorderLayout());

    m_data = new PropertyTableData(m_bean);
    m_table = new JTable(m_data);

    JScrollPane ps = new JScrollPane();
    ps.getViewport().add(m_table);
    getContentPane().add(ps, BorderLayout.CENTER);

    setDefaultCloseOperation(HIDE_ON_CLOSE);
    setVisible(true);
  }

  public void propertyChange(PropertyChangeEvent evt) {
    m_data.setProperty(evt.getPropertyName(), evt.getNewValue());
  }

  class PropertyTableData extends AbstractTableModel 
  {
    protected String[][] m_properties;
    protected int m_numProps = 0;
    protected Vector m_v;

    public PropertyTableData(Component bean) {
      try {
        BeanInfo info = Introspector.getBeanInfo(
          m_bean.getClass());
        BeanDescriptor descr = info.getBeanDescriptor();
        setTitle("Editing "+descr.getName());
        PropertyDescriptor[] props = info.getPropertyDescriptors();
        m_numProps = props.length;
                
        m_v = new Vector(m_numProps);
        for (int k=0; k<m_numProps; k++) {
          String name = props[k].getDisplayName();
          boolean added = false;
          for (int i=0; i<m_v.size(); i++) {
            String str = ((PropertyDescriptor)m_v.elementAt(i)).
              getDisplayName();
            if (name.compareToIgnoreCase(str) < 0) {
              m_v.insertElementAt(props[k], i);
              added = true;
              break;
            }
          }
          if (!added)
            m_v.addElement(props[k]);
        }

        m_properties = new String[m_numProps][2];
        for (int k=0; k<m_numProps; k++) {
          PropertyDescriptor prop = 
            (PropertyDescriptor)m_v.elementAt(k);
          m_properties[k][0] = prop.getDisplayName();
          Method mRead = prop.getReadMethod();
          if (mRead != null && 
           mRead.getParameterTypes().length == 0) {
            Object value = mRead.invoke(m_bean, null);
            m_properties[k][1] = objToString(value);
          }
          else
            m_properties[k][1] = "error";
        }
      }
      catch (Exception ex) {
        ex.printStackTrace();
        JOptionPane.showMessageDialog(
          BeanEditor.this, "Error: "+ex.toString(),
          "Warning", JOptionPane.WARNING_MESSAGE);
      }
    }

    public void setProperty(String name, Object value) {
      for (int k=0; k<m_numProps; k++)
        if (name.equals(m_properties[k][0])) {
          m_properties[k][1] = objToString(value);
          m_table.tableChanged(new TableModelEvent(this, k)); 
          m_table.repaint();
          break;
        }
    }

    public int getRowCount() { return m_numProps; }

    public int getColumnCount() { return 2; } 

    public String getColumnName(int nCol) { 
      return nCol==0 ? "Property" : "Value";
    }
 
    public boolean isCellEditable(int nRow, int nCol) { 
       return (nCol==1);
    }

    public Object getValueAt(int nRow, int nCol) {
      if (nRow < 0 || nRow>=getRowCount())
        return "";
      switch (nCol) {
        case 0: return m_properties[nRow][0];
        case 1: return m_properties[nRow][1];
      }
      return "";
    }

    public void setValueAt(Object value, int nRow, int nCol) {
      if (nRow < 0 || nRow>=getRowCount())
        return;
      String str = value.toString();
      PropertyDescriptor prop = (PropertyDescriptor)m_v.
        elementAt(nRow);
      Class cls = prop.getPropertyType();
      Object obj = stringToObj(str, cls);
      if (obj==null)
        return;        // can't process
           
      Method mWrite = prop.getWriteMethod();
      if (mWrite == null || mWrite.getParameterTypes().length != 1)
        return;
      try {
        mWrite.invoke(m_bean, new Object[]{ obj });
        m_bean.getParent().doLayout();
        m_bean.getParent().repaint();
        m_bean.repaint();
      }
      catch (Exception ex) {
        ex.printStackTrace();
        JOptionPane.showMessageDialog(
          BeanEditor.this, "Error: "+ex.toString(),
          "Warning", JOptionPane.WARNING_MESSAGE);
      }
      m_properties[nRow][1] = str;
    }

    public String objToString(Object value) {
      if (value==null)
        return "null";
      if (value instanceof Dimension) {
        Dimension dim = (Dimension)value;
        return ""+dim.width+","+dim.height;
      }
      else if (value instanceof Insets) {
        Insets ins = (Insets)value;
        return ""+ins.left+","+ins.top+","+ins.right+","+ins.bottom;
      }
      else if (value instanceof Rectangle) {
        Rectangle rc = (Rectangle)value;
        return ""+rc.x+","+rc.y+","+rc.width+","+rc.height;
      }
      else if (value instanceof Color) {
        Color col = (Color)value;
        return ""+col.getRed()+","+col.getGreen()+","+col.getBlue();
      }
      return value.toString();
    }

    public Object stringToObj(String str, Class cls) {
      try {
        if (str==null)
          return null;
        String name = cls.getName();
        if (name.equals("java.lang.String"))
          return str;
        else if (name.equals("int"))
          return new Integer(str);
        else if (name.equals("long"))
          return new Long(str);
        else if (name.equals("float"))
          return new Float(str);
        else if (name.equals("double"))
          return new Double(str);
        else if (name.equals("boolean"))
          return new Boolean(str);
        else if (name.equals("java.awt.Dimension")) {
          int[] i = strToInts(str);
          return new Dimension(i[0], i[1]);
        }
        else if (name.equals("java.awt.Insets")) {
          int[] i = strToInts(str);
          return new Insets(i[0], i[1], i[2], i[3]);
        }
        else if (name.equals("java.awt.Rectangle")) {
          int[] i = strToInts(str);
          return new Rectangle(i[0], i[1], i[2], i[3]);
        }
        else if (name.equals("java.awt.Color")) {
          int[] i = strToInts(str);
          return new Color(i[0], i[1], i[2]);
        }
        return null;    // not supported
      }
      catch(Exception ex) { return null; }
    }

    public int[] strToInts(String str) throws Exception {
      int[] i = new int[4];
      StringTokenizer tokenizer = new StringTokenizer(str, ",");
      for (int k=0; k<i.length && 
       tokenizer.hasMoreTokens(); k++)
        i[k] = Integer.parseInt(tokenizer.nextToken());
      return i;
    }
  }
}

This class (formerly BeanContainer from section 4.7) has received a new collection, Hashtable m_editors, added as an instance variable. This Hashtable holds references to BeanEditor frames (used to edit beans, see below) as values and the corresponding Components being edited as keys.

A new menu item titled "Properties..." is added to the "Edit" menu. This item is used to create a new editor for the selected bean or activate an existing one (if any). The attached ActionListener looks for an existing BeanEditor corresponding to the currently selected m_activeBean component in the m_editors collection. If such an editor is found it is made visible and brought to the front. Otherwise, a new instance of BeanEditor is created to edit the currently active m_activeBean component, and is added to the ! m_editors collection.

The ActionListener attached to menu item "Delete," which removes the currently active component, receives additional functionality. The added code looks for an existing BeanEditor corresponding to the currently selected m_activeBean component in the m_editors collection. If such an editor is found it is disposed and its’ reference is removed from the hashtable.

This class extends JFrame and implements the PropertyChangeListener interface. BeanEditor is used to display and edit the properties exposed by a given JavaBean. Three instance variables are declared:

The BeanEditor constructor takes a reference to the JavaBean component to be edited, and stores it in instance variable m_bean. The initial location of the editor frame is selected depending on the location of the component being edited.

The table component, m_table, is created and added to a JScrollPane to provide scrolling capabilities. Note that we do not add a WindowListener to this frame. Instead we use the HIDE_ON_CLOSE default close operation (see chapter 3):

Upon closing, this frame will be hidden but not disposed. Its’ reference will still be present in the m_editors collection, and this frame will be re-activated if the user chooses to see the properties of the associated bean again.

Note that an instance of the BeanEditor class is added as a PropertyChangeListener to the corresponding bean being edited. The propertyChange() method is invoked if the bean has changed it's state during editing and a PropertyChangeEvent has been fired. This method simply triggers a call to the setProperty() method of the table model.

PropertyTableData extends AbstractTableModel and provides the table model for each bean editor. Three instance variables are declared:

The constructor of the PropertyTableData class takes a given bean instance and retrieves it's properties. First it uses the Introspector.getBeanInfo() method to get a BeanInfo instance:

      BeanInfo info = Introspector.getBeanInfo(m_bean.getClass());
      BeanDescriptor descr = info.getBeanDescriptor();
      setTitle("Editing "+descr.getName());
      PropertyDescriptor[] props = info.getPropertyDescriptors();
      m_numProps = props.length;

This provides us with all available information about a bean (see chapter 2). We determine the bean's name and use it as the editor frame's title (note that this is an inner class, so setTitle() refers to the parent BeanEditor instance). We then extract an array of PropertyDescriptors which will provide us with the actual information about a bean's properties.

Bean properties are sorted by name in alphabetical order. The name of each property is determined with the getDisplayName() method. The sorted PropertyDescriptors are stored in our m_v Vector collection. Then we can create the 2-dimensional array, m_properties, which holds data to be displayed in the table. This array has m_numProps rows and 2 columns (for property name and value). To determine a property’s value we need to obtain a reference to its getXX() ! method with getReadMethod() and make a call using the reflection API. We can call only getXX() methods without parameters (since we don’t know anything about these parameters). Note that our objToString() helper method is invoked to translate a property’s value into a display string (see below).

The setProperty() method searches for the given name in the 0-th column of the m_properties array. If such a property is found this method sets it’s new value and updates the table component.

Several other simple methods included in this class have already been presented in previous examples and need not be explained again here. However, note that the isCellEditable() method returns true only for cells in the second column (property names, obviously, cannot be changed).

The setValueAt() method deserves additional explanation because it not only saves the modified data in the table model, but it also sends these modifications to the bean component itself. To do this we obtain a PropertyDescriptor instance stored in the m_v Vector collection. The modified property value is always a String, so first we need to convert it into its proper object type using our stringToObj() helper method (if we can do this, see below). If the conversion succeeds (i.e. the result is not null), we can continue.

To modify a bean value we determine the reference to it's setXX()method (corresponding to a certain property) and invoke it. Note that an anonymous array containing one element is used as parameter (these constructions are typical when dealing with the reflection API). Then the bean component and it's container (which can also be affected by changes in such properties as size and color) are refreshed to reflect the bean’s new property value. Finally, if the above procedures were successful, we store the new value in the m_properties data array.

The objToString() helper method converts a given Object into a String suitable for editing. In many cases the toString() method returns a long string starting with the class name. This is not very appropriate for editable data values. So for several classes we provide our own conversion into a string of comma-delimited numbers. For instance a Dimension object is converted into a "width, height" form, Color is converted into "red, green, blue" form, etc. If no special implementation is provided, an object'! s toString() string is returned.

The stringToObj() helper method converts a given String into an Object of the given Class. The class's name is analyzed and a conversion method is chosen to build the correct type of object based on this name. The simplest case is the String class: we don't need to do any conversion at all in this case. For the primitive data types such as int or boolean we return the corresponding encapsulating (wrapper class) objects. For the several classes which receive spec! ial treatment in the objToString() method (such as a Dimension or Color object), we parse the comma-delimited string of numbers and construct the proper object. For all other classes (or if a parsing exception occurs) we return null to indicate that we cannot perform the required conversion.

Figure 18.9 shows the BeanContainer container and two editing frames displaying the properties of Clock and JButton components. This application provides a simple but powerful tool for investigating Swing and AWT components as well as custom JavaBeans. We can see all exposed properties and modify many of them. If a component’s properties change as a result of user interaction, our component properly notifies its’ listeners and we see an automatic editor table update. Try serializing a modified component and restoring it from its’ file. Note how the previously modified properties are saved as expected.

It is natural to imagine using this example as a base for constructing a custom Swing IDE (Interface Development Environment). BeanContainer, combined with the custom resize edge components developed in chapters 15 and 16, provides a fairly powerful base to work from.