Restricting editable length of a JTable column

Question

Hello,
Is there a way to restrict the length of a JTable cell when being edited? i.e. I have a column of my JTable that should only contain strings of 3 characters at the most.
Many thanks,
Ian.

Answer 1

Hello,
import javax.swing.*;
import javax.swing.text.*;
public class TestCustomTable extends JFrame implements TableData
     public static void main(String[] args)
          new TestCustomTable();
     private JTable customTable = null;
     public TestCustomTable()
          setDefaultCloseOperation(EXIT_ON_CLOSE);
          initTable();
          pack();
          setLocationRelativeTo(null);
          setVisible(true);
     private void initTable()
          customTable = new JTable(DATA, COLHEADS);
          //create custom-TextField with maximum Characters
          MaxCharTextField maxCharField = new MaxCharTextField(3);
          DefaultCellEditor maxCharEditor = new DefaultCellEditor(maxCharField);
                //all Objects in the table have the same restriction
          customTable.setDefaultEditor(Object.class, maxCharEditor);
          getContentPane().add(new JScrollPane(customTable));
* MaxCharTextField.java
class MaxCharTextField extends JTextField
     int maxChar = 10;
     public MaxCharTextField()
          super();
     public MaxCharTextField(int maxChar)
          super();
          this.maxChar = maxChar;
     public void setMaxChar(int maxChar)
          this.maxChar = maxChar;
     public int getMaxChar()
          return maxChar;
     protected Document createDefaultModel()
          return new PlainDocument()
               public void insertString(int offs, String str, AttributeSet a)
                    throws BadLocationException
                    int length = getLength();
                    // fields don't want to have multiple lines.  We may provide a field-specific
                    // model in the future in which case the filtering logic here will no longer
                    // be needed.
                    Object filterNewlines = getProperty("filterNewlines");
                    if ((filterNewlines instanceof Boolean)
                         && filterNewlines.equals(Boolean.TRUE))
                         if ((str != null) && (str.indexOf('\n') >= 0))
                              StringBuffer filtered = new StringBuffer(str);
                              int n = filtered.length();
                              for (int i = 0; i < n; i++)
                                   if (filtered.charAt(i) == '\n')
                                        filtered.setCharAt(i, ' ');
                              str = filtered.toString();
                    if ((length += str.length()) > maxChar)
                         //don't insert if current chars > max chars
                         return;
                    super.insertString(offs, str, a);
* TableData.java
* test-data for custom table
interface TableData
     public static final Object[][] DATA =
          { { "Mary", "Campione", "Snowboarding", new Integer(5), new Boolean(false)}, {
               "Alison", "Huml", "Rowing", new Integer(3), new Boolean(true)
               "Kathy",
                    "Walrath",
                    "Chasing toddlers",
                    new Integer(2),
                    new Boolean(false)
               "Sharon",
                    "Zakhour",
                    "Speed reading",
                    new Integer(20),
                    new Boolean(true)
               "Angela",
                    "Lih",
                    "Teaching high school",
                    new Integer(4),
                    new Boolean(false)
     public static final String[] COLHEADS =
          { "First Name", "Last Name", "Sport", "# of Years", "Vegetarian" };
}regards,
Tim