Updated: Displaying a jTable inside another jTable // JTable cellRenderer

// We initialize the Objects where we'll store our data
// First an array Object which will be our main table
Object[][] data = null;
// We create an Array String to hold the name of the main table columns
//In this example case we are going to store a contact name,
//his email address(es) and his phone numer(s)
//We're also going to store the creation date.
String[] columns = {"Name", "E-Mail","Phone","Creation Date"};

public void populateData() {
  // Two contacts
  data = new Object[3][columns.length];
  data[0][0] = "Peter";
  String[] emails = {"peter@yahoo.com", "strange@name.com"};
  data[0][1] = emails;
  String[] phones = {"555 35 25 65" , "555 35 24 63"};
  data[0][2] = phones;
  data[0][3] = new Date();
  data[1][0] = "Jackson";
  data[1][1] = "Jack@hotmail.com";
  String[] phones2 = {"555 35 24 33" , "555 11 88 88", "332 55 25 34"};
  data[1][2] = phones2;
  data[1][3] = new Date();
  data[2][0] = "Robert";
  data[2][1] = "rob@hotmail.com";
  data[2][2] = "555 28 95 81";
  data[2][3] = new Date();
  // As you can see, we've stored two contacts one with two e-mail
  // accounts and two phone numbers, and another member with three phone numbers
}

// Next we create our table models
public void createModel(){
  /* First we create the main model We overide the AbstractTableModel necessary methods*/
  AbstractTableModel modelo = new AbstractTableModel() {
    public String getColumnName(int col) {
      return columns[col];
    }
    public Class getColumnClass(int col) {
      if(getRowCount() <1) {
        return null;
      }
      return data[0][col].getClass();
    }
    public int getRowCount() {
      return data.length;
    }
    public int getColumnCount() {
      return columns.length;
    }
    public Object getValueAt(int row, int col) {
      return data[row][col];
    }
    public boolean isCellEditable(int row, int col){
      return true;
    }
    public void setValueAt(Object value, int row, int col) {
      data[row][col] = value;
      fireTableCellUpdated(row, col);
    }
  };
  // We apply the model to the main jTable
  jTableData.setModel(modelo);
  // We create a cell Renderer to display the data of the multivalue fields
  TableCellRenderer jTableCellRenderer = new TableCellRenderer() {
    /* Magic Happens */
    public Component getTableCellRendererComponent(
        JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
      /* If what we're displaying isn't an array of values we return the normal renderer*/
      if(!value.getClass().isArray()){
        return table.getDefaultRenderer(value.getClass())
            .getTableCellRendererComponent( table, value, isSelected, hasFocus,row, column);
      } else {
        final Object[] passed = (Object[])value;
        //  We create the table that will hold the multivalue
        // fields and that will be embedded in the main table
        JTable embedded = new JTable(new AbstractTableModel() {
          public int getColumnCount() {
            return 1;
          }
          public int getRowCount() {
            return passed.length;
          }
          public Object getValueAt(int rowIndex, int columnIndex) {
            return passed[rowIndex];
          }
          public boolean isCellEditable(int row, int col){
            return true;
          }
        });
        if(isSelected){
          embedded.setBackground(jTableData.getSelectionBackground());
          embedded.setForeground(jTableData.getSelectionForeground());
        }
        if(hasFocus){
          embedded.setRowSelectionInterval(0,1);
        }
        // If this is what you plan to enable mouseClick detection,
        // in your table, IT WONT WORK. Have a look at TableCellEditor.
        embedded.addMouseListener(new MouseAdapter() {
          public void mouseClicked(java.awt.event.MouseEvent evt) {
            System.out.println("PEPE");
          }
        });
        setPreferredSize(embedded.getPreferredSize());
        if(getPreferredSize().height != table.getRowHeight(row)) {
          table.setRowHeight(row, getPreferredSize().height);
        }
        return embedded;
      }
    }
  };
  // Finally we apply the new cellRenderer to the whole table
  TableColumnModel tcm = jTableData.getColumnModel();
  for(int it = 0; it < tcm.getColumnCount(); it++){
    tcm.getColumn(it).setCellRenderer(jTableCellRenderer);
    // tcm.getColumn(it).setCellEditor(jTableCellEditor);
  }
  // Note: if we need to edit the values inside the embedded jtable
  // we will need to create a TableCellEditor too.
}