Java DefaultListCellRenderer extend

import java.awt.Color;
import java.awt.Component;
import java.awt.FlowLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.DefaultListCellRenderer;
import javax.swing.DefaultListModel;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
import javax.swing.UIManager;
import javax.swing.border.Border;
import javax.swing.border.EmptyBorder;

public class Main extends JFrame {
  public Main() {
    super("");

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLayout(new FlowLayout());

    CheckBoxList list = new CheckBoxList();
    DefaultListModel model = (DefaultListModel)list.getModel();
    model.addElement(new CheckBoxListEntry("CSS", true));
    model.addElement(new CheckBoxListEntry("HTML", true));
    model.addElement(new CheckBoxListEntry("Java", false));
    model.addElement(new CheckBoxListEntry("Javascript", true));
    //  ww w  . j  a va 2  s.  c  o  m

    getContentPane().add(new JScrollPane(list));
  }

  public static void main(String[] args) {
    Main frame = new Main();
    frame.pack();
    frame.setVisible(true);
  }
}
 class CheckBoxList extends JList {

  public CheckBoxList() {
    super();

    setModel(new DefaultListModel());
    setCellRenderer(new CheckboxCellRenderer());

    addMouseListener(new MouseAdapter() {
      @Override
      public void mousePressed(MouseEvent e) {
        int index = locationToIndex(e.getPoint());

        if (index != -1) {
          Object obj = getModel().getElementAt(index);
          if (obj instanceof JCheckBox) {
            JCheckBox checkbox = (JCheckBox) obj;

            checkbox.setSelected(!checkbox.isSelected());
            repaint();
          }
        }
      }
    }

    );

    setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
  }

  @SuppressWarnings("unchecked")
  public int[] getCheckedIdexes() {
    java.util.List list = new java.util.ArrayList();
    DefaultListModel dlm = (DefaultListModel) getModel();
    for (int i = 0; i < dlm.size(); ++i) {
      Object obj = getModel().getElementAt(i);
      if (obj instanceof JCheckBox) {
        JCheckBox checkbox = (JCheckBox) obj;
        if (checkbox.isSelected()) {
          list.add(new Integer(i));
        }
      }
    }

    int[] indexes = new int[list.size()];

    for (int i = 0; i < list.size(); ++i) {
      indexes[i] = ((Integer) list.get(i)).intValue();
    }

    return indexes;
  }

  @SuppressWarnings("unchecked")
  public java.util.List getCheckedItems() {
    java.util.List list = new java.util.ArrayList();
    DefaultListModel dlm = (DefaultListModel) getModel();
    for (int i = 0; i < dlm.size(); ++i) {
      Object obj = getModel().getElementAt(i);
      if (obj instanceof JCheckBox) {
        JCheckBox checkbox = (JCheckBox) obj;
        if (checkbox.isSelected()) {
          list.add(checkbox);
        }
      }
    }
    return list;
  }
}
class CheckboxCellRenderer extends DefaultListCellRenderer {
  protected static Border noFocusBorder = new EmptyBorder(1, 1, 1, 1);

  public Component getListCellRendererComponent(JList list, Object value, int index,
      boolean isSelected, boolean cellHasFocus) {
    if (value instanceof CheckBoxListEntry) {
      CheckBoxListEntry checkbox = (CheckBoxListEntry) value;
      checkbox.setBackground(isSelected ? list.getSelectionBackground() : list.getBackground());
      if (checkbox.isRed()) {
        checkbox.setForeground(Color.red);
      } else {
        checkbox.setForeground(isSelected ? list.getSelectionForeground() : list.getForeground());
      }
      checkbox.setEnabled(isEnabled());
      checkbox.setFont(getFont());
      checkbox.setFocusPainted(false);
      checkbox.setBorderPainted(true);
      checkbox.setBorder(isSelected ? UIManager.getBorder("List.focusCellHighlightBorder")
          : noFocusBorder);

      return checkbox;
    } else {
      return super.getListCellRendererComponent(list, value.getClass().getName(), index,
          isSelected, cellHasFocus);
    }
  }
}
class CheckBoxListEntry extends JCheckBox {

  private Object value = null;

  private boolean red = false;

  public CheckBoxListEntry(Object itemValue, boolean selected) {
    super(itemValue == null ? "" : "" + itemValue, selected);
    setValue(itemValue);
  }

  public boolean isSelected() {
    return super.isSelected();
  }

  public void setSelected(boolean selected) {
    super.setSelected(selected);
  }

  public Object getValue() {
    return value;
  }

  public void setValue(Object value) {
    this.value = value;
  }

  public boolean isRed() {
    return red;
  }

  public void setRed(boolean red) {
    this.red = red;
  }

}