Creating a JTable with multiple row headers

Courtesy of Nobuo Tamemasa (http://www2.gol.com/users/tame/swing/examples/JTableExamples1.htm7)



MultipleRowHeaderExample.java:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.event.*;
   
/*   ----------------------------------------------
 *  |         SNo.        |
 *   ----------------------------------------------
 *  |          |     1    |
 *  |   Name   |-----------------------------------
 *  |          |     2    |
 *   ----------------------------------------------
 *  |          |     1    |
 *  |          |-----------------------------------
 *  | Language |     2    |
 *  |          |-----------------------------------
 *  |          |     3    |
 *   ----------------------------------------------
 */
 
/**
 * @version 1.0 03/06/99
 */
public class MultipleRowHeaderExample extends JFrame {
  Object[][] data;
  Object[] column;
  JTable table;
  MultiSpanCellTable fixedTable;
 
  public MultipleRowHeaderExample() {
    super( "Multiple Row Header Example" );
    setSize( 400, 150 );
    
    data =  new Object[][]{
        {"SNo."    ,"" },
        {"Name"    ,"1"},
        {""        ,"2"},
        {"Language","1"},
        {""        ,"2"},
        {""        ,"3"}};
    column = new Object[]{"",""};
    
    AttributiveCellTableModel fixedModel = new AttributiveCellTableModel(data, column) {
      public boolean CellEditable(int row, int col) { 
        return false; 
      }
    };
        
    CellSpan cellAtt =(CellSpan)fixedModel.getCellAttribute();
    cellAtt.combine(new int[] {0}    ,new int[] {0,1});
    cellAtt.combine(new int[] {1,2}  ,new int[] {0});
    cellAtt.combine(new int[] {3,4,5},new int[] {0});
    
    DefaultTableModel    model = new DefaultTableModel(data.length, 3);
        
    fixedTable = new MultiSpanCellTable( fixedModel );
    table = new JTable( model );
    fixedTable.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
    fixedTable.setDefaultRenderer(Object.class, new RowHeaderRenderer(fixedTable));
    fixedTable.setGridColor(table.getTableHeader().getBackground());
    
    JScrollPane scroll = new JScrollPane( table );
    JViewport viewport = new JViewport();
    viewport.setView(fixedTable);
    viewport.setPreferredSize(fixedTable.getPreferredSize());
    scroll.setRowHeaderView(viewport);
    
    getContentPane().add(scroll, BorderLayout.CENTER);
  }
 
  public static void main(String[] args) {
    MultipleRowHeaderExample frame = new MultipleRowHeaderExample();
    frame.addWindowListener( new WindowAdapter() {
      public void windowClosing( WindowEvent e ) {
        System.exit(0);
      }
    });
    frame.setVisible(true);
  }
  
  class RowHeaderRenderer extends JLabel implements TableCellRenderer {  
    RowHeaderRenderer(JTable table) {
      JTableHeader header = table.getTableHeader();
      setOpaque(true);
      setBorder(UIManager.getBorder("TableHeader.cellBorder"));
      setHorizontalAlignment(CENTER);
      setForeground(header.getForeground());
      setBackground(header.getBackground());
      setFont(header.getFont());
    }
   
    public Component getTableCellRendererComponent(JTable table, Object value,
                          boolean isSelected, boolean hasFocus, int row, int column) {
      setText((value == null) ? "" : value.toString());
      return this;
    }
  }
  
}

AttributiveCellTableModel.java:

import java.util.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.event.*;
 
/**
 * @version 1.0 11/22/98
 */
 
public class AttributiveCellTableModel extends DefaultTableModel {
 
  protected CellAttribute cellAtt;
     
  public AttributiveCellTableModel() {
    this((Vector)null, 0);
  }
  public AttributiveCellTableModel(int numRows, int numColumns) {
    Vector names = new Vector(numColumns);
    names.setSize(numColumns);
    setColumnIdentifiers(names);
    dataVector = new Vector();
    setNumRows(numRows);
    cellAtt = new DefaultCellAttribute(numRows,numColumns);
  }
  public AttributiveCellTableModel(Vector columnNames, int numRows) {
    setColumnIdentifiers(columnNames);
    dataVector = new Vector();
    setNumRows(numRows);
    cellAtt = new DefaultCellAttribute(numRows,columnNames.size());
  }
  public AttributiveCellTableModel(Object[] columnNames, int numRows) {
    this(convertToVector(columnNames), numRows);
  }  
  public AttributiveCellTableModel(Vector data, Vector columnNames) {
    setDataVector(data, columnNames);
  }
  public AttributiveCellTableModel(Object[][] data, Object[] columnNames) {
    setDataVector(data, columnNames);
  }
     
  public void setDataVector(Vector newData, Vector columnNames) {
    if (newData == null)
      throw new IllegalArgumentException("setDataVector() - Null parameter");
    dataVector = new Vector(0);
    setColumnIdentifiers(columnNames);
    dataVector = newData;
     
    //
    cellAtt = new DefaultCellAttribute(dataVector.size(),
                                       columnIdentifiers.size());
     
    newRowsAdded(new TableModelEvent(this, 0, getRowCount()-1,
                 TableModelEvent.ALL_COLUMNS, TableModelEvent.INSERT));
  }
 
  public void addColumn(Object columnName, Vector columnData) {
    if (columnName == null)
      throw new IllegalArgumentException("addColumn() - null parameter");
    columnIdentifiers.addElement(columnName);
    int index = 0;
    Enumeration enumeration = dataVector.elements();
    while (enumeration.hasMoreElements()) {
      Object value;
      if ((columnData != null) && (index < columnData.size()))
          value = columnData.elementAt(index);
      else
        value = null;
      ((Vector)enumeration.nextElement()).addElement(value);
      index++;
    }
 
    //
    cellAtt.addColumn();

    fireTableStructureChanged();
  }
 
  public void addRow(Vector rowData) {
    Vector newData = null;
    if (rowData == null) {
      newData = new Vector(getColumnCount());
    }
    else {
      rowData.setSize(getColumnCount());
    }
    dataVector.addElement(newData);
 
    //
    cellAtt.addRow();
 
    newRowsAdded(new TableModelEvent(this, getRowCount()-1, getRowCount()-1,
       TableModelEvent.ALL_COLUMNS, TableModelEvent.INSERT));
  }
 
  public void insertRow(int row, Vector rowData) {
    if (rowData == null) {
      rowData = new Vector(getColumnCount());
    }
    else {
      rowData.setSize(getColumnCount());
    }
 
    dataVector.insertElementAt(rowData, row);
 
    //
    cellAtt.insertRow(row);
 
    newRowsAdded(new TableModelEvent(this, row, row,
       TableModelEvent.ALL_COLUMNS, TableModelEvent.INSERT));
  }
  
  public CellAttribute getCellAttribute() {
    return cellAtt;
  }
 
  public void setCellAttribute(CellAttribute newCellAtt) {
    int numColumns = getColumnCount();
    int numRows    = getRowCount();
    if ((newCellAtt.getSize().width  != numColumns) ||
        (newCellAtt.getSize().height != numRows)) {
      newCellAtt.setSize(new Dimension(numRows, numColumns));
    }
    cellAtt = newCellAtt;
    fireTableDataChanged();
  }
 
  /*
  public void changeCellAttribute(int row, int column, Object command) {
    cellAtt.changeAttribute(row, column, command);
  }
 
  public void changeCellAttribute(int[] rows, int[] columns, Object command) {
    cellAtt.changeAttribute(rows, columns, command);
  }
  */
}

DefaultCellAttribute.java:

import java.awt.*;
 
/**
 * @version 1.0 11/22/98
 */
 
public class DefaultCellAttribute 
//    implements CellAttribute ,CellSpan  {
      implements CellAttribute ,CellSpan ,ColoredCell ,CellFont {
 
  //
  // !!!! CAUTION !!!!!
  // these values must be synchronized to Table data
  //
  protected int rowSize;
  protected int columnSize;
  protected int[][][] span;                   // CellSpan
  protected Color[][] foreground;             // ColoredCell
  protected Color[][] background;             //
  protected Font[][]  font;                   // CellFont
   
  public DefaultCellAttribute() {
    this(1,1);
  }
   
  public DefaultCellAttribute(int numRows, int numColumns) {
    setSize(new Dimension(numColumns, numRows));
  }
 
  protected void initValue() {
    for(int i=0; i<span.length;i++) {
      for(int j=0; j<span[i].length; j++) {
        span[i][j][CellSpan.COLUMN] = 1;
        span[i][j][CellSpan.ROW]    = 1;
      }
    }
  }
 
 
  //
  // CellSpan
  //
  public int[] getSpan(int row, int column) {
    if (isOutOfBounds(row, column)) {
      int[] ret_code = {1,1};
      return ret_code;
    }
    return span[row][column];
  }
 
  public void setSpan(int[] span, int row, int column) {
    if (isOutOfBounds(row, column)) return;
    this.span[row][column] = span;
  }
       
  public boolean isVisible(int row, int column) {
    if (isOutOfBounds(row, column)) return false;
    if ((span[row][column][CellSpan.COLUMN] < 1)
      ||(span[row][column][CellSpan.ROW]    < 1)) return false;
    return true;
  }
 
  public void combine(int[] rows, int[] columns) {
    if (isOutOfBounds(rows, columns)) return;
    int    rowSpan  = rows.length;
    int columnSpan  = columns.length;
    int startRow    = rows[0];
    int startColumn = columns[0];
    for (int i=0;i<rowSpan;i++) {
      for (int j=0;j<columnSpan;j++) {
        if ((span[startRow +i][startColumn +j][CellSpan.COLUMN] != 1)
          ||(span[startRow +i][startColumn +j][CellSpan.ROW]    != 1)) {
          //System.out.println("can't combine");
          return ;
        }
      }
    }
    for (int i=0,ii=0;i<rowSpan;i++,ii--) {
      for (int j=0,jj=0;j<columnSpan;j++,jj--) {
        span[startRow +i][startColumn +j][CellSpan.COLUMN] = jj;
        span[startRow +i][startColumn +j][CellSpan.ROW]    = ii;
        //System.out.println("r " +ii +"  c " +jj);
      }
    }
    span[startRow][startColumn][CellSpan.COLUMN] = columnSpan;
    span[startRow][startColumn][CellSpan.ROW]    =    rowSpan;
    
  }
 
  public void split(int row, int column) {
    if (isOutOfBounds(row, column)) return;
    int columnSpan = span[row][column][CellSpan.COLUMN];
    int    rowSpan = span[row][column][CellSpan.ROW];
    for (int i=0;i<rowSpan;i++) {
      for (int j=0;j<columnSpan;j++) {
        span[row +i][column +j][CellSpan.COLUMN] = 1;
        span[row +i][column +j][CellSpan.ROW]    = 1;
      }
    }
  }
 
 
  //
  // ColoredCell
  //
  public Color getForeground(int row, int column) {
    if (isOutOfBounds(row, column)) return null;
    return foreground[row][column];
  }
  public void setForeground(Color color, int row, int column) {
    if (isOutOfBounds(row, column)) return;
    foreground[row][column] = color;
  }
  public void setForeground(Color color, int[] rows, int[] columns) {
    if (isOutOfBounds(rows, columns)) return;
    setValues(foreground, color, rows, columns);
  }
  public Color getBackground(int row, int column) {
    if (isOutOfBounds(row, column)) return null;
    return background[row][column];
  }
  public void setBackground(Color color, int row, int column) {
    if (isOutOfBounds(row, column)) return;
    background[row][column] = color;
  }
  public void setBackground(Color color, int[] rows, int[] columns) {
    if (isOutOfBounds(rows, columns)) return;
    setValues(background, color, rows, columns);
  }
  //
 
 
  //
  // CellFont
  //
  public Font getFont(int row, int column) {
    if (isOutOfBounds(row, column)) return null;
    return font[row][column];
  }
  public void setFont(Font font, int row, int column) {
    if (isOutOfBounds(row, column)) return;
    this.font[row][column] = font;
  }
  public void setFont(Font font, int[] rows, int[] columns) {
    if (isOutOfBounds(rows, columns)) return;
    setValues(this.font, font, rows, columns);
  }
  //
 
 
  //
  // CellAttribute
  //
  public void addColumn() {
    int[][][] oldSpan = span;
    int numRows    = oldSpan.length;
    int numColumns = oldSpan[0].length;
    span = new int[numRows][numColumns + 1][2];
    System.arraycopy(oldSpan,0,span,0,numRows);
    for (int i=0;i<numRows;i++) {
      span[i][numColumns][CellSpan.COLUMN] = 1;
      span[i][numColumns][CellSpan.ROW]    = 1;
    }
  }
 
  public void addRow() {
    int[][][] oldSpan = span;
    int numRows    = oldSpan.length;
    int numColumns = oldSpan[0].length;
    span = new int[numRows + 1][numColumns][2];
    System.arraycopy(oldSpan,0,span,0,numRows);
    for (int i=0;i<numColumns;i++) {
      span[numRows][i][CellSpan.COLUMN] = 1;
      span[numRows][i][CellSpan.ROW]    = 1;
    }
  }
 
  public void insertRow(int row) {
    int[][][] oldSpan = span;
    int numRows    = oldSpan.length;
    int numColumns = oldSpan[0].length;
    span = new int[numRows + 1][numColumns][2];
    if (0 < row) {
      System.arraycopy(oldSpan,0,span,0,row-1);
    }
    System.arraycopy(oldSpan,0,span,row,numRows - row);
    for (int i=0;i<numColumns;i++) {
      span[row][i][CellSpan.COLUMN] = 1;
      span[row][i][CellSpan.ROW]    = 1;
    }
  }
 
  public Dimension getSize() {
    return new Dimension(rowSize, columnSize);
  }
 
  public void setSize(Dimension size) {
    columnSize = size.width;
    rowSize    = size.height;
    span = new int[rowSize][columnSize][2];   // 2: COLUMN,ROW
    foreground = new Color[rowSize][columnSize];
    background = new Color[rowSize][columnSize];
    font = new Font[rowSize][columnSize];
    initValue();
  }
 
  /*
  public void changeAttribute(int row, int column, Object command) {
  }
 
  public void changeAttribute(int[] rows, int[] columns, Object command) {
  }
  */
 
  protected boolean isOutOfBounds(int row, int column) {
    if ((row    < 0)||(rowSize    <= row)
      ||(column < 0)||(columnSize <= column)) {
      return true;
    }
    return false;
  }
 
  protected boolean isOutOfBounds(int[] rows, int[] columns) {
    for (int i=0;i<rows.length;i++) {
      if ((rows[i] < 0)||(rowSize <= rows[i])) return true;
    }
    for (int i=0;i<columns.length;i++) {
      if ((columns[i] < 0)||(columnSize <= columns[i])) return true;
    }
    return false;
  }
 
  protected void setValues(Object[][] target, Object value,
                           int[] rows, int[] columns) {
    for (int i=0;i<rows.length;i++) {
      int row = rows[i];
      for (int j=0;j<columns.length;j++) {
        int column = columns[j];
        target[row][column] = value;
      }
    }
  }
}

CellAttribute.java:

import java.awt.*;
 
/**
 * @version 1.0 11/22/98
 */ 
public interface CellAttribute {
 
  public void addColumn();
 
  public void addRow();
 
  public void insertRow(int row);
 
  public Dimension getSize();
 
  public void setSize(Dimension size);
}

ColoredCell.java:

import java.awt.*;
 
/**
 * @version 1.0 11/22/98
 */
 
public interface ColoredCell {
  public Color getForeground(int row, int column);
  public void setForeground(Color color, int row, int column);
  public void setForeground(Color color, int[] rows, int[] columns);
 
  public Color getBackground(int row, int column);
  public void setBackground(Color color, int row, int column);
  public void setBackground(Color color, int[] rows, int[] columns);
}

CellFont.java:

import java.awt.*;
 
/**
 * @version 1.0 11/22/98
 */
 
public interface CellFont {
  public Font getFont(int row, int column);
  public void setFont(Font font, int row, int column);
  public void setFont(Font font, int[] rows, int[] columns);
}

CellSpan.java:

/**
 * @version 1.0 11/22/98
 */
 
public interface CellSpan {
  public final int ROW    = 0;
  public final int COLUMN = 1;
   
  public int[] getSpan(int row, int column);
  public void setSpan(int[] span, int row, int column);
   
  public boolean isVisible(int row, int column);
   
  public void combine(int[] rows, int[] columns);
  public void split(int row, int column);

}

MultiSpanCellTable.java:

import java.util.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.plaf.basic.*;
import javax.swing.event.*;
 
/**
 * @version 1.0 11/26/98
 */
 
public class MultiSpanCellTable extends JTable {
 
  public MultiSpanCellTable(TableModel model) {
    super(model);
    setUI(new MultiSpanCellTableUI());
    getTableHeader().setReorderingAllowed(false);
    setCellSelectionEnabled(true);
    setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
  }
  
  public Rectangle getCellRect(int row, int column, boolean includeSpacing) {
    Rectangle sRect = super.getCellRect(row,column,includeSpacing);
    if ((row <0) || (column<0) ||
        (getRowCount() <= row) || (getColumnCount() <= column)) {
        return sRect;
    }
    CellSpan cellAtt = (CellSpan)((AttributiveCellTableModel)getModel()).getCellAttribute();
    if (! cellAtt.isVisible(row,column)) {
      int temp_row    = row;
      int temp_column = column;
      row    += cellAtt.getSpan(temp_row,temp_column)[CellSpan.ROW];
      column += cellAtt.getSpan(temp_row,temp_column)[CellSpan.COLUMN];      
    }
    int[] n = cellAtt.getSpan(row,column);
 
    int index = 0;
    int columnMargin = getColumnModel().getColumnMargin();
    Rectangle cellFrame = new Rectangle();
    int aCellHeight = rowHeight + rowMargin;
    cellFrame.y = row * aCellHeight;
    cellFrame.height = n[CellSpan.ROW] * aCellHeight;
    
    Enumeration enumeration = getColumnModel().getColumns();
    while (enumeration.hasMoreElements()) {
      TableColumn aColumn = (TableColumn)enumeration.nextElement();
      cellFrame.width = aColumn.getWidth() + columnMargin;
      if (index == column) break;
      cellFrame.x += cellFrame.width;
      index++;
    }
    for (int i=0;i< n[CellSpan.COLUMN]-1;i++) {
      TableColumn aColumn = (TableColumn)enumeration.nextElement();
      cellFrame.width += aColumn.getWidth() + columnMargin;
    }
     
    if (!includeSpacing) {
      Dimension spacing = getIntercellSpacing();
      cellFrame.setBounds(cellFrame.x +      spacing.width/2,
                          cellFrame.y +      spacing.height/2,
                          cellFrame.width -  spacing.width,
                          cellFrame.height - spacing.height);
    }
    return cellFrame;
  }
  
  
  private int[] rowColumnAtPoint(Point point) {
    int[] retValue = {-1,-1};
    int row = point.y / (rowHeight + rowMargin);
    if ((row <0)||(getRowCount() <= row)) return retValue;
    int column = getColumnModel().getColumnIndexAtX(point.x);
 
    CellSpan cellAtt = (CellSpan)((AttributiveCellTableModel)getModel()).getCellAttribute();
 
    if (cellAtt.isVisible(row,column)) {
      retValue[CellSpan.COLUMN] = column;
      retValue[CellSpan.ROW   ] = row;
      return retValue;
    }
    retValue[CellSpan.COLUMN] = column + cellAtt.getSpan(row,column)[CellSpan.COLUMN];
    retValue[CellSpan.ROW   ] = row + cellAtt.getSpan(row,column)[CellSpan.ROW];
    return retValue;
  }
 
  public int rowAtPoint(Point point) {
    return rowColumnAtPoint(point)[CellSpan.ROW];
  }
  public int columnAtPoint(Point point) {
    return rowColumnAtPoint(point)[CellSpan.COLUMN];
  }
 
 
  
  public void columnSelectionChanged(ListSelectionEvent e) {
    repaint();
  }
 
  public void valueChanged(ListSelectionEvent e) {
    int firstIndex = e.getFirstIndex();
    int  lastIndex = e.getLastIndex();
    if (firstIndex == -1 && lastIndex == -1) { // Selection cleared.
      repaint();
    }
    Rectangle dirtyRegion = getCellRect(firstIndex, 0, false);
    int numCoumns = getColumnCount();
    int index = firstIndex;
    for (int i=0;i<numCoumns;i++) {
      dirtyRegion.add(getCellRect(index, i, false));
    }
    index = lastIndex;
    for (int i=0;i<numCoumns;i++) {
      dirtyRegion.add(getCellRect(index, i, false));
    }
    repaint(dirtyRegion.x, dirtyRegion.y, dirtyRegion.width, dirtyRegion.height);
  }
 
}

MultiSpanCellTableUI.java:

import java.util.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.plaf.basic.*;
 
/**
 * @version 1.0 11/26/98
 */
 
public class MultiSpanCellTableUI extends BasicTableUI {
 
  public void paint(Graphics g, JComponent c) {
    Rectangle oldClipBounds = g.getClipBounds();
    Rectangle clipBounds    = new Rectangle(oldClipBounds);
    int tableWidth   = table.getColumnModel().getTotalColumnWidth();
    clipBounds.width = Math.min(clipBounds.width, tableWidth);
    g.setClip(clipBounds);
 
    int firstIndex = table.rowAtPoint(new Point(0, clipBounds.y));
    int  lastIndex = table.getRowCount()-1;
 
    Rectangle rowRect = new Rectangle(0,0,
      tableWidth, table.getRowHeight() + table.getRowMargin());
    rowRect.y = firstIndex*rowRect.height;
 
    for (int index = firstIndex; index <= lastIndex; index++) {
      if (rowRect.intersects(clipBounds)) {
        //System.out.println();                  // debug
        //System.out.print("" + index +": ");    // row
        paintRow(g, index);
      }
      rowRect.y += rowRect.height;
    }
    g.setClip(oldClipBounds);
  }
 
  private void paintRow(Graphics g, int row) {
    Rectangle rect = g.getClipBounds();
    boolean drawn  = false;
    
    AttributiveCellTableModel tableModel = (AttributiveCellTableModel)table.getModel();
    CellSpan cellAtt = (CellSpan)tableModel.getCellAttribute();
    int numColumns = table.getColumnCount();
 
    for (int column = 0; column < numColumns; column++) {
      Rectangle cellRect = table.getCellRect(row,column,true);
      int cellRow,cellColumn;
      if (cellAtt.isVisible(row,column)) {
        cellRow    = row;
        cellColumn = column;
          //  System.out.print("   "+column+" ");  // debug
      } else {
        cellRow    = row + cellAtt.getSpan(row,column)[CellSpan.ROW];
        cellColumn = column + cellAtt.getSpan(row,column)[CellSpan.COLUMN];
          //  System.out.print("  ("+column+")");  // debug
      }
      if (cellRect.intersects(rect)) {
        drawn = true;
        paintCell(g, cellRect, cellRow, cellColumn);
      } else {
        if (drawn) break;
      } 
    }
  }
 
  private void paintCell(Graphics g, Rectangle cellRect, int row, int column) {
    int spacingHeight = table.getRowMargin();
    int spacingWidth  = table.getColumnModel().getColumnMargin();
 
    Color c = g.getColor();
    g.setColor(table.getGridColor());
    g.drawRect(cellRect.x,cellRect.y,cellRect.width-1,cellRect.height-1);
    g.setColor(c);
 
    cellRect.setBounds(cellRect.x + spacingWidth/2, cellRect.y + spacingHeight/2,
                       cellRect.width - spacingWidth, cellRect.height - spacingHeight);
 
    if (table.isEditing() && table.getEditingRow()==row &&
        table.getEditingColumn()==column) {
      Component component = table.getEditorComponent();
      component.setBounds(cellRect);
      component.validate();
    }
    else {
      TableCellRenderer renderer = table.getCellRenderer(row, column);
      Component component = table.prepareRenderer(renderer, row, column);
 
      if (component.getParent() == null) {
        rendererPane.add(component);
      }
      rendererPane.paintComponent(g, component, table, cellRect.x, cellRect.y,
                                  cellRect.width, cellRect.height, true);
    }
  }    
}

Programmatically scroll a scrollable JTable to a specific cell or row

The scrollRectToVisible method is the magic one you need. The code fragment below assumes that selectedColumn and selectedRow indicate the cell that you want to make sure is visible. If your rows/columns are not all the same height/width you will have to change the calculations, but the concept is the same.

   table.scrollRectToVisible(
      new Rectangle(columnWidth*selectedColumn,
                    table.getRowHeight()*(selectedRow),
                    columnWidth,
                    table.getRowHeight()));

Getting the caret row and column positions on my JTextPane

Main.java:

import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
import java.awt.*;
 
public class Main extends JFrame {
   public Main() {
      setTitle("CaretPosition demo");
 
      final JEditorPane ep = new JEditorPane();
  
      JPanel panel = new JPanel(new FlowLayout(FlowLayout.LEFT));
 
      panel.add(new JLabel("Row:"));
      final JTextField rowTextField = new JTextField(5);
      rowTextField.setEditable(false);
      panel.add(rowTextField);
 
      panel.add(new JLabel("Col:"));
      final JTextField colTextField = new JTextField(5);
      colTextField.setEditable(false);
      panel.add(colTextField);
 
      getContentPane().add(BorderLayout.NORTH, panel);
      getContentPane().add(BorderLayout.CENTER, ep);
 
      ep.addCaretListener(new CaretListener() {
         public void caretUpdate(CaretEvent ce) {
            int pos = ep.getCaretPosition();
            Element map = ep.getDocument().getDefaultRootElement();
            int row = map.getElementIndex(pos);
            Element lineElem = map.getElement(row);
            int col = pos - lineElem.getStartOffset();
 
            rowTextField.setText(""+row);
            colTextField.setText(""+col);
         }
      });
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(300, 300);
      main.setVisible(true);        
   }
}

Writing out a DOM subtree to System.out

You can use the XSLT Transformer class to do this.

Here’s an example.

Test.xml

<?xml version="1.0" encoding="UTF-8"?>
<message>
   <content>Hello World!</content>
   <destinations>
      <dest>jmsqueue:myjmsqueue</dest>
      <dest>file:/home/filequeue</dest>
      <dest>123.30.230.90</dest>
   </destinations>
</message>

Main.java:

import org.w3c.dom.*;
 
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.dom.DOMSource;
  
import java.io.*;
 
public class Main
{
   public static void main(String []args) {
      Document doc;
  
      try {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         doc = db.parse(new File("test.xml"));
 
         NodeList nodeList = doc.getElementsByTagName("destinations");
         Node node = nodeList.item(0);
  
         // use the XSLT transformation package to output the subtree destinations
         TransformerFactory tf = TransformerFactory.newInstance();
         Transformer transformer = tf.newTransformer();
         transformer.transform(new DOMSource(node), new StreamResult(System.out));
      }
      catch(Exception e) {
         e.printStackTrace();
      }
   } 
}

outputs:

<?xml version="1.0" encoding="UTF-8"?>
<destinations>
      <dest>jmsqueue:myjmsqueue</dest>
      <dest>file:/home/filequeue</dest>
      <dest>123.30.230.90</dest>
   </destinations>

Return binary data with a Servlet

There are a couple possibilities. One way (if the binary file is in the subtree of your docroot) is to do a redirection inside your servlet to the binary file as shown in following example:

GetFileThroughServlet1.java:

import javax.servlet.http.*;
import javax.servlet.*;
 
import java.io.*;
 
public class GetFileThroughServlet1 extends HttpServlet
{ 
   public void doGet (HttpServletRequest request,
                       HttpServletResponse response) 
   {
      try {
         response.sendRedirect("http://www.yourdomain.com/test.zip");
      } catch (Exception e) {
      }
   }
}

A second, more flexible way, is to return a file as a binary stream. The file doesn’t need to be in the subtree of a docroot, for example you can get it off the network or from a database.

GetFileThroughServlet2.java:

import javax.servlet.http.*;
import javax.servlet.*;
 
import java.io.*;
 
public class GetFileThroughServlet2 extends HttpServlet
{ 
   public void doGet (HttpServletRequest request,
                       HttpServletResponse response) 
   {
      try {
         String pathToFile = "/dir1/dir2/dir3/";
         String fileToUpload = "test.zip"; 
         int filesize = 40768;   // test.zip filesize
  
         // set content type to octet-stream = binary file
         response.setContentType("application/octet-stream");
  
         // Content-Disposition is a field to specify presentation of entity or file name
         response.setHeader("Content-Disposition", "attachment; filename="" + fileToUpload + "";");
 
         response.setHeader("Cache-Control", "no-cache");         
 
         response.setContentLength(filesize);
 
         ServletOutputStream sos = response.getOutputStream(); 
         BufferedInputStream bis = new BufferedInputStream(new FileInputStream(pathToFile + fileToUpload)); 
         int data; 
         while((data = bis.read()) != -1) {  
            sos.write(data); 
         }  
         bis.close(); 
         sos.close();
      }
      catch(Exception e) {
      }
   }
}

Programmatically getting column information of a database table in Java

You can get meta information on a table by invoking getMetaData on a connection. With the method getColumns, you get back a number of rows containing information about each column of a particular table. Check the api to see what you can query.

Main.java:

import java.util.*;
import java.text.*;
import java.sql.*;
  
public class Main {
   public static void main(String []args) throws Exception {
      try {
         Class.forName("org.gjt.mm.mysql.Driver").newInstance();
         Connection conn = DriverManager.getConnection("jdbc:mysql://192.168.0.1/esus", 
                                                       "joris",
                                                       "mypass");
 
         DatabaseMetaData dbMeta = conn.getMetaData();
         ResultSet rs = dbMeta.getColumns(null, "", "orders", "%");
 
         while (rs.next()) {
            String column_name      = rs.getString(4);
            String sql_type         = rs.getString(5);
            String type_name        = rs.getString(6);
            String column_size      = rs.getString(7);
            String ordinal_position = rs.getString(17);
            String is_nullable      = rs.getString(18);
 
            System.out.println("Column " + column_name);
            System.out.println("tSQL_TYPE          = " + sql_type);
            System.out.println("tTYPE_NAME         = " + type_name);
            System.out.println("tCOLUMN_SIZE       = " + column_size);
            System.out.println("tORDINAL_POSITION  = " + ordinal_position);
            System.out.println("tIS_NULLABLE       = " + is_nullable);
         } 
      }
      catch(Exception e) {
         e.printStackTrace();
      }
   } 
}

outputs:

Column orderid
	SQL_TYPE          = 4
	TYPE_NAME         = int
	COLUMN_SIZE       = 10
	ORDINAL_POSITION  = 1
	IS_NULLABLE       = NO
Column custid
	SQL_TYPE          = 4
	TYPE_NAME         = int
	COLUMN_SIZE       = 10
	ORDINAL_POSITION  = 2
	IS_NULLABLE       = YES
Column timestamp
	SQL_TYPE          = 93
	TYPE_NAME         = datetime
	COLUMN_SIZE       = 19
	ORDINAL_POSITION  = 3
	IS_NULLABLE       = YES
Column status
	SQL_TYPE          = -6
	TYPE_NAME         = tinyint
	COLUMN_SIZE       = 4
	ORDINAL_POSITION  = 4
	IS_NULLABLE       = YES

Find out where a class has been loaded from

Main.java:

public class Main
{
   public static void main(String []args) throws Exception {
      String className = "/java/lang/String.class";
      String loadedFrom = "" + (new Object().getClass().getResource(className));
 
      System.out.println(loadedFrom);
   }
}

outputs:

jar:file:/C:/jdk1.2.2/jre/lib/rt.jar!/java/lang/String.class

Getting the list of network interfaces installed on your machine

If you have multiple IP addresses on one machine, it may be useful to specify which one to use for your networking stuff. Since JDK1.4, you can enumerate them and select one with the class java.net.NetworkInterface.

Main.java:

import java.util.*;
import java.net.*;
 
public class Main
{
   public static void main(String []args) {
      try {
         Enumeration enum = NetworkInterface.getNetworkInterfaces();
         while (enum.hasMoreElements()) {
            NetworkInterface ni = (NetworkInterface) enum.nextElement();
            System.out.println(ni);
         }
      }
      catch(SocketException e) {
         e.printStackTrace();
      }
   }
}

outputs on my Win2000 machine:

name:lan0 (Intel DC21140 PCI Fast Ethernet Adapter) index: 1 addresses:
/192.168.2.10;

name:lan1 (Intel DC21140 PCI Fast Ethernet Adapter) index: 2 addresses:

name:lo0 (MS TCP Loopback interface) index: 3 addresses:
/127.0.0.1;

Creating an underlined JLabel without using HTML

Main.java:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
public class Main extends JFrame
{
   public Main() {
      getContentPane().setLayout(new GridLayout(1, 2));
      JPanel panel1 = new JPanel();
      panel1.setLayout(new GridLayout(5, 1));
      panel1.add(new JLabel(&quot;JLabel/icon/LEFT&quot;, 
                           new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.LEFT));
      panel1.add(new JLabel(&quot;JLabel/icon/CENTER&quot;, 
                           new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.CENTER));
      panel1.add(new JLabel(&quot;JLabel/icon/RIGHT&quot;, 
                           new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.RIGHT));
      panel1.add(new JLabel(&quot;JLabel/icon/LEADING&quot;, 
                           new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.LEADING));
      panel1.add(new JLabel(&quot;JLabel/icon/TRAILING&quot;, 
                           new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.TRAILING));
 
      getContentPane().add(new JScrollPane(panel1));
 
      JPanel panel2 = new JPanel();
      panel2.setLayout(new GridLayout(5, 1));
      panel2.add(new UnderlinedJLabel(&quot;JLabel/icon/LEFT&quot;, 
                                      new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.LEFT));
      panel2.add(new UnderlinedJLabel(&quot;JLabel/icon/CENTER&quot;, 
                                      new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.CENTER));
      panel2.add(new UnderlinedJLabel(&quot;JLabel/icon/RIGHT&quot;, 
                                      new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.RIGHT));
      panel2.add(new UnderlinedJLabel(&quot;JLabel/icon/LEADING&quot;, 
                                      new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.LEADING));
      panel2.add(new UnderlinedJLabel(&quot;JLabel/icon/TRAILING&quot;, 
                                      new ImageIcon(&quot;tiffIcon.gif&quot;), SwingConstants.TRAILING));
 
      getContentPane().add(new JScrollPane(panel2));
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      });
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(300, 150);
      main.setVisible(true);   
   }
}
 
class UnderlinedJLabel extends JLabel
{
   public UnderlinedJLabel() {
   }
 
   public UnderlinedJLabel(Icon image) {
      super(image);
   }
 
   public UnderlinedJLabel(Icon image, int horizontalAlignment) {
      super(image, horizontalAlignment);
   }
 
   public UnderlinedJLabel(String text) {
      super(text);
   }

   public UnderlinedJLabel(String text, Icon icon, int horizontalAlignment) {
      super(text, icon, horizontalAlignment);
   }
 
   public UnderlinedJLabel(String text, int horizontalAlignment) {
      super(text, horizontalAlignment);
   }
 
   public void paint(Graphics g) {
      super.paint(g);
      underline(g);
   }
 
   protected void underline(Graphics g) {
      Insets insets = getInsets();
      FontMetrics fm = g.getFontMetrics();
      Rectangle textR = new Rectangle();
      Rectangle viewR = new Rectangle(
                                  insets.left, 
                                  insets.top, 
                                  getWidth() - (insets.right + insets.left), 
                                  getHeight() - (insets.bottom + insets.top));
  
      // compute and return location of the icons origin,
      // the location of the text baseline, and a possibly clipped
      // version of the compound label string.  Locations are computed 
      // relative to the viewR rectangle.
      String text = SwingUtilities.layoutCompoundLabel(
                         this,                        // this JLabel
                         fm,                          // current FontMetrics
                         getText(),                   // text
                         getIcon(),                   // icon
                         getVerticalAlignment(),      
                         getHorizontalAlignment(),
                         getVerticalTextPosition(),
                         getHorizontalTextPosition(), 
                         viewR,                       
                         new Rectangle(),             // don't care about icon rectangle
                         textR,                       // resulting text locations
                         getText() == null ? 0 : 
                            ((Integer)UIManager.get(&quot;Button.textIconGap&quot;)).intValue());
 
      // draw line
      int textShiftOffset = ((Integer) UIManager.get(&quot;Button.textShiftOffset&quot;)).intValue();
      g.fillRect(textR.x +
                 textShiftOffset - 4,
                 textR.y + fm.getAscent() + textShiftOffset + 2,
                 textR.width, 
                 1);
   }
}