Add tool tips to a JTable using a renderer in Java

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import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;

import javax.swing.DefaultCellEditor;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumn;

public class Main extends JPanel {
  private boolean DEBUG = false;

  public Main() {
    super(new GridLayout(1, 0));

    JTable table = new JTable(new MyTableModel());
    table.setPreferredScrollableViewportSize(new Dimension(500, 70));

    // Create the scroll pane and add the table to it.
    JScrollPane scrollPane = new JScrollPane(table);

    // Set up column sizes.
    initColumnSizes(table);

    // Fiddle with the Sport column's cell editors/renderers.
    setUpSportColumn(table, table.getColumnModel().getColumn(2));

    // Add the scroll pane to this panel.
    add(scrollPane);
  }

  /*
   * This method picks good column sizes. If all column heads are wider than the
   * column's cells' contents, then you can just use column.sizeWidthToFit().
   */
  private void initColumnSizes(JTable table) {
    MyTableModel model = (MyTableModel) table.getModel();
    TableColumn column = null;
    Component comp = null;
    int headerWidth = 0;
    int cellWidth = 0;
    Object[] longValues = model.longValues;
    TableCellRenderer headerRenderer = table.getTableHeader().getDefaultRenderer();

    for (int i = 0; i < 5; i++) {
      column = table.getColumnModel().getColumn(i);

      comp = headerRenderer.getTableCellRendererComponent(null, column.getHeaderValue(), false,
          false, 0, 0);
      headerWidth = comp.getPreferredSize().width;

      comp = table.getDefaultRenderer(model.getColumnClass(i)).getTableCellRendererComponent(table,
          longValues[i], false, false, 0, i);
      cellWidth = comp.getPreferredSize().width;

      if (DEBUG) {
        System.out.println("Initializing width of column " + i + ". " + "headerWidth = "
            + headerWidth + "; cellWidth = " + cellWidth);
      }

      // XXX: Before Swing 1.1 Beta 2, use setMinWidth instead.
      column.setPreferredWidth(Math.max(headerWidth, cellWidth));
    }
  }

  public void setUpSportColumn(JTable table, TableColumn sportColumn) {
    // Set up the editor for the sport cells.
    JComboBox comboBox = new JComboBox();
    comboBox.addItem("Snowboarding");
    comboBox.addItem("Rowing");
    comboBox.addItem("Knitting");
    comboBox.addItem("Speed reading");
    comboBox.addItem("Pool");
    comboBox.addItem("None of the above");
    sportColumn.setCellEditor(new DefaultCellEditor(comboBox));

    // Set up tool tips for the sport cells.
    DefaultTableCellRenderer renderer = new DefaultTableCellRenderer();
    renderer.setToolTipText("Click for combo box");
    sportColumn.setCellRenderer(renderer);
  }

  class MyTableModel extends AbstractTableModel {
    private String[] columnNames = { "First Name", "Last Name", "Sport", "# of Years", "Vegetarian" };

    private Object[][] data = {
        { "Mary", "Campione", "Snowboarding", new Integer(5), new Boolean(false) },
        { "Alison", "Huml", "Rowing", new Integer(3), new Boolean(true) },
        { "Kathy", "Walrath", "Knitting", new Integer(2), new Boolean(false) },
        { "Sharon", "Zakhour", "Speed reading", new Integer(20), new Boolean(true) },
        { "Philip", "Milne", "Pool", new Integer(10), new Boolean(false) } };

    public final Object[] longValues = { "Sharon", "Campione", "None of the above",
        new Integer(20), Boolean.TRUE };

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

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

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

    public Object getValueAt(int row, int col) {
      return data[row][col];
    }

    /*
     * JTable uses this method to determine the default renderer/ editor for
     * each cell. If we didn't implement this method, then the last column would
     * contain text ("true"/"false"), rather than a check box.
     */
    public Class getColumnClass(int c) {
      return getValueAt(0, c).getClass();
    }

    /*
     * Don't need to implement this method unless your table's editable.
     */
    public boolean isCellEditable(int row, int col) {
      // Note that the data/cell address is constant,
      // no matter where the cell appears onscreen.
      if (col < 2) {
        return false;
      } else {
        return true;
      }
    }

    /*
     * Don't need to implement this method unless your table's data can change.
     */
    public void setValueAt(Object value, int row, int col) {
      if (DEBUG) {
        System.out.println("Setting value at " + row + "," + col + " to " + value
            + " (an instance of " + value.getClass() + ")");
      }

      data[row][col] = value;
      fireTableCellUpdated(row, col);

   
    }

  }

  public static void main(String[] args) {
    JFrame frame = new JFrame("TableRenderDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Create and set up the content pane.
    Main newContentPane = new Main();
    newContentPane.setOpaque(true); // content panes must be opaque
    frame.setContentPane(newContentPane);

    // Display the window.
    frame.pack();
    frame.setVisible(true);
  }
}


/*
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 * Copyright (c) 1998 Sun Microsystems, Inc. All Rights Reserved.
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