path: root/libjava/classpath/javax/swing/DefaultListSelectionModel.java

/* DefaultListSelectionModel.java --
   Copyright (C) 2002, 2004, 2005 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02110-1301 USA.

Linking this library statically or dynamically with other modules is
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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modules, and to copy and distribute the resulting executable under
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package javax.swing;

import java.io.Serializable;
import java.util.BitSet;
import java.util.EventListener;

import javax.swing.event.EventListenerList;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

/**
 * The default implementation of {@link ListSelectionModel},
 * which is used by {@link javax.swing.JList} and
 * similar classes to manage the selection status of a number of data
 * elements.
 *
 * <p>The class is organized <em>abstractly</em> as a set of intervals of
 * integers. Each interval indicates an inclusive range of indices in a
 * list -- held by some other object and unknown to this class -- which is
 * considered "selected". There are various accessors for querying and
 * modifying the set of intervals, with simplified forms accepting a single
 * index, representing an interval with only one element. </p>
 */
public class DefaultListSelectionModel implements Cloneable,
                                                  ListSelectionModel,
                                                  Serializable
{
  private static final long serialVersionUID = -5718799865110415860L;

  /** The list of ListSelectionListeners subscribed to this selection model. */
  protected EventListenerList listenerList = new EventListenerList();


  /**
   * The current list selection mode. Must be one of the numeric constants
   * <code>SINGLE_SELECTION</code>, <code>SINGLE_INTERVAL_SELECTION</code>
   * or <code>MULTIPLE_INTERVAL_SELECTION</code> from {@link
   * ListSelectionModel}. The default value is
   * <code>MULTIPLE_INTERVAL_SELECTION</code>.
   */
  int selectionMode = MULTIPLE_INTERVAL_SELECTION;

  /**
   * The index of the "lead" of the most recent selection. The lead is the
   * second argument in any call to {@link #setSelectionInterval}, {@link
   * #addSelectionInterval} or {@link #removeSelectionInterval}. Generally
   * the lead refers to the most recent position a user dragged their mouse
   * over.
   */
  int leadSelectionIndex = -1;

  /**
   * The index of the "anchor" of the most recent selection. The anchor is
   * the first argument in any call to {@link #setSelectionInterval},
   * {@link #addSelectionInterval} or {@link
   * #removeSelectionInterval}. Generally the anchor refers to the first
   * recent position a user clicks when they begin to drag their mouse over
   * a list.
   *
   * @see #getAnchorSelectionIndex
   * @see #setAnchorSelectionIndex
   */
  int anchorSelectionIndex = -1;

  /**
   * controls the range of indices provided in any {@link
   * ListSelectionEvent} fired by the selectionModel. Let
   * <code>[A,L]</code> be the range of indices between {@link
   * #anchorSelectionIndex} and {@link #leadSelectionIndex} inclusive, and
   * let <code>[i0,i1]</code> be the range of indices changed in a given
   * call which generates a {@link ListSelectionEvent}. Then when this
   * property is <code>true</code>, the {@link ListSelectionEvent} contains
   * the range <code>[A,L] union [i0,i1]</code>; when <code>false</code> it
   * will contain only <code>[i0,i1]</code>. The default is
   * <code>true</code>.
   *
   * @see #isLeadAnchorNotificationEnabled
   * @see #setLeadAnchorNotificationEnabled
   */
  protected boolean leadAnchorNotificationEnabled = true;

  /**
   * Whether the selection is currently "adjusting". Any {@link
   * ListSelectionEvent} events constructed in response to changes in this
   * list selection model will have their {@link
   * ListSelectionEvent#isAdjusting} field set to this value.
   *
   * @see #getValueIsAdjusting
   * @see #setValueIsAdjusting
   */
  boolean valueIsAdjusting = false;


  /**
   * The current set of "intervals", represented simply by a {@link
   * java.util.BitSet}. A set bit indicates a selected index, whereas a
   * cleared bit indicates a non-selected index.
   */
  BitSet sel = new BitSet();

  /**
   * A variable to store the previous value of sel.
   * Used to make sure we only fireValueChanged when the BitSet
   * actually does change.
   */
  Object oldSel;

  /**
   * Whether this call of setLeadSelectionInterval was called locally
   * from addSelectionInterval
   */
  boolean setLeadCalledFromAdd = false;

  /**
   * Returns the selection mode, which is one of {@link #SINGLE_SELECTION},
   * {@link #SINGLE_INTERVAL_SELECTION} and
   * {@link #MULTIPLE_INTERVAL_SELECTION}.  The default value is
   * {@link #MULTIPLE_INTERVAL_SELECTION}.
   *
   * @return The selection mode.
   *
   * @see #setSelectionMode(int)
   */
  public int getSelectionMode()
  {
    return selectionMode;
  }

  /**
   * Sets the value of the {@link #selectionMode} property.
   *
   * @param mode The new value of the property
   */
  public void setSelectionMode(int mode)
  {
    if (mode < ListSelectionModel.SINGLE_SELECTION
        || mode > ListSelectionModel.MULTIPLE_INTERVAL_SELECTION)
      throw new IllegalArgumentException("Unrecognised mode: " + mode);
    selectionMode = mode;
  }

  /**
   * Gets the value of the {@link #anchorSelectionIndex} property.
   *
   * @return The current property value
   *
   * @see #setAnchorSelectionIndex
   */
  public int getAnchorSelectionIndex()
  {
    return anchorSelectionIndex;
  }

  /**
   * Sets the value of the {@link #anchorSelectionIndex} property.
   *
   * @param index The new property value
   *
   * @see #getAnchorSelectionIndex
   */
  public void setAnchorSelectionIndex(int index)
  {
    if (anchorSelectionIndex != index)
      {
        int old = anchorSelectionIndex;
        anchorSelectionIndex = index;
        if (leadAnchorNotificationEnabled)
          fireValueChanged(index, old);
      }
  }

  /**
   * Gets the value of the {@link #leadSelectionIndex} property.
   *
   * @return The current property value
   *
   * @see #setLeadSelectionIndex
   */
  public int getLeadSelectionIndex()
  {
    return leadSelectionIndex;
  }

  /**
   * <p>Sets the value of the {@link #anchorSelectionIndex} property. As a
   * side effect, alters the selection status of two ranges of indices. Let
   * <code>OL</code> be the old lead selection index, <code>NL</code> be
   * the new lead selection index, and <code>A</code> be the anchor
   * selection index. Then if <code>A</code> is a valid selection index,
   * one of two things happens depending on the seleciton status of
   * <code>A</code>:</p>
   *
   * <ul>
   *
   * <li><code>isSelectedIndex(A) == true</code>: set <code>[A,OL]</code>
   * to <em>deselected</em>, then set <code>[A,NL]</code> to
   * <em>selected</em>.</li>
   *
   * <li><code>isSelectedIndex(A) == false</code>: set <code>[A,OL]</code>
   * to <em>selected</em>, then set <code>[A,NL]</code> to
   * <em>deselected</em>.</li>
   *
   * </ul>
   *
   * <p>This method generates at most a single {@link ListSelectionEvent}
   * despite changing multiple ranges. The range of values provided to the
   * {@link ListSelectionEvent} includes only the minimum range of values
   * which changed selection status between the beginning and end of the
   * method.</p>
   *
   * @param leadIndex The new property value
   *
   * @see #getAnchorSelectionIndex
   */
  public void setLeadSelectionIndex(int leadIndex)
  {
    // Only set the lead selection index to < 0 if anchorSelectionIndex < 0.
    if (leadIndex < 0)
      {
        if (anchorSelectionIndex < 0)
          leadSelectionIndex = -1;
        else
          return;
      }

    // Only touch the lead selection index if the anchor is >= 0.
    if (anchorSelectionIndex < 0)
      return;

    if (selectionMode == SINGLE_SELECTION)
      setSelectionInterval (leadIndex, leadIndex);

    int oldLeadIndex = leadSelectionIndex;
    if (oldLeadIndex == -1)
      oldLeadIndex = leadIndex;
    if (setLeadCalledFromAdd == false)
      oldSel = sel.clone();
    leadSelectionIndex = leadIndex;

    if (anchorSelectionIndex == -1)
      return;

    int R1 = Math.min(anchorSelectionIndex, oldLeadIndex);
    int R2 = Math.max(anchorSelectionIndex, oldLeadIndex);
    int S1 = Math.min(anchorSelectionIndex, leadIndex);
    int S2 = Math.max(anchorSelectionIndex, leadIndex);

    int lo = Math.min(R1, S1);
    int hi = Math.max(R2, S2);

    if (isSelectedIndex(anchorSelectionIndex))
      {
        sel.clear(R1, R2+1);
        sel.set(S1, S2+1);
      }
    else
      {
        sel.set(R1, R2+1);
        sel.clear(S1, S2+1);
      }

    int beg = sel.nextSetBit(0), end = -1;
    for(int i=beg; i >= 0; i=sel.nextSetBit(i+1))
      end = i;

    BitSet old = (BitSet) oldSel;

    // The new and previous lead location requires repainting.
    old.set(oldLeadIndex, !sel.get(oldLeadIndex));
    old.set(leadSelectionIndex, !sel.get(leadSelectionIndex));

    fireDifference(sel, old);
  }

  /**
   * Moves the lead selection index to <code>leadIndex</code> without
   * changing the selection values.
   *
   * If leadAnchorNotificationEnabled is true, send a notification covering the
   * old and new lead cells.
   *
   * @param leadIndex the new lead selection index
   * @since 1.5
   */
  public void moveLeadSelectionIndex (int leadIndex)
  {
    if (leadSelectionIndex == leadIndex)
      return;

    leadSelectionIndex = leadIndex;
    if (isLeadAnchorNotificationEnabled())
      fireValueChanged(Math.min(leadSelectionIndex, leadIndex),
                       Math.max(leadSelectionIndex, leadIndex));
  }

  /**
   * Gets the value of the {@link #leadAnchorNotificationEnabled} property.
   *
   * @return The current property value
   *
   * @see #setLeadAnchorNotificationEnabled
   */
  public boolean isLeadAnchorNotificationEnabled()
  {
    return leadAnchorNotificationEnabled;
  }

  /**
   * Sets the value of the {@link #leadAnchorNotificationEnabled} property.
   *
   * @param l The new property value
   *
   * @see #isLeadAnchorNotificationEnabled
   */
  public void setLeadAnchorNotificationEnabled(boolean l)
  {
    leadAnchorNotificationEnabled = l;
  }

  /**
   * Gets the value of the {@link #valueIsAdjusting} property.
   *
   * @return The current property value
   *
   * @see #setValueIsAdjusting
   */
  public boolean getValueIsAdjusting()
  {
    return valueIsAdjusting;
  }

  /**
   * Sets the value of the {@link #valueIsAdjusting} property.
   *
   * @param v The new property value
   *
   * @see #getValueIsAdjusting
   */
  public void setValueIsAdjusting(boolean v)
  {
    valueIsAdjusting = v;
  }

  /**
   * Determines whether the selection is empty.
   *
   * @return <code>true</code> if the selection is empty, otherwise
   * <code>false</code>
   */
  public boolean isSelectionEmpty()
  {
    return sel.isEmpty();
  }

  /**
   * Gets the smallest index which is currently a member of a selection
   * interval.
   *
   * @return The least integer <code>i</code> such that <code>i >=
   *     0</code> and <code>i</code> is a member of a selected interval, or
   *     <code>-1</code> if there are no selected intervals
   *
   * @see #getMaxSelectionIndex
   */
  public int getMinSelectionIndex()
  {
    if (isSelectionEmpty())
      return -1;

    return sel.nextSetBit(0);
  }

  /**
   * Gets the largest index which is currently a member of a selection
   * interval.
   *
   * @return The greatest integer <code>i</code> such that <code>i >=
   *     0</code> and <code>i</code> is a member of a selected interval, or
   *     <code>-1</code> if there are no selected intervals
   *
   * @see #getMinSelectionIndex
   */
  public int getMaxSelectionIndex()
  {
    if (isSelectionEmpty())
      return -1;

    int mx = -1;
    for(int i=sel.nextSetBit(0); i >= 0; i=sel.nextSetBit(i+1))
      {
        mx = i;
      }
    return mx;
  }

  /**
   * Determines whether a particular index is a member of a selection
   * interval.
   *
   * @param a The index to search for
   *
   * @return <code>true</code> if the index is a member of a selection interval,
   *     otherwise <code>false</code>
   */
  public boolean isSelectedIndex(int a)
  {
    // TODO: Probably throw an exception here?
    if (a >= sel.length() || a < 0)
      return false;
    return sel.get(a);
  }

  /**
   * If the {@link #selectionMode} property is equal to
   * <code>SINGLE_SELECTION</code> equivalent to calling
   * <code>setSelectionInterval(index1, index2)</code>;
   * If the {@link #selectionMode} property is equal to
   * <code>SINGLE_INTERVAL_SELECTION</code> and the interval being
   * added is not adjacent to an already selected interval,
   * equivalent to <code>setSelectionInterval(index1, index2)</code>.
   * Otherwise adds the range <code>[index0, index1]</code>
   * to the selection interval set.
   *
   * @param index0 The beginning of the range of indices to select
   * @param index1 The end of the range of indices to select
   *
   * @see #setSelectionInterval
   * @see #removeSelectionInterval
   */
  public void addSelectionInterval(int index0, int index1)
  {
    if (index0 == -1 || index1 == -1)
      return;

    if (selectionMode == SINGLE_SELECTION)
      setSelectionInterval(index0, index1);
    else
    {
    int lo = Math.min(index0, index1);
    int hi = Math.max(index0, index1);
    oldSel = sel.clone();


    // COMPAT: Like Sun (but not like IBM), we allow calls to
    // addSelectionInterval when selectionMode is
    // SINGLE_SELECTION_INTERVAL iff the interval being added
    // is adjacent to an already selected interval
    if (selectionMode == SINGLE_INTERVAL_SELECTION)
      if (!(isSelectedIndex(index0) ||
            isSelectedIndex(index1) ||
            isSelectedIndex(Math.max(lo-1,0)) ||
            isSelectedIndex(Math.min(hi+1,sel.size()))))
        sel.clear();

    // We have to update the anchorSelectionIndex and leadSelectionIndex
    // variables

    // The next if statements breaks down to "if this selection is adjacent
    // to the previous selection and going in the same direction"
    if ((isSelectedIndex(leadSelectionIndex))
        && ((index0 - 1 == leadSelectionIndex
             && (index1 >= index0)
             && (leadSelectionIndex >= anchorSelectionIndex))
            || (index0 + 1 == leadSelectionIndex && (index1 <= index0)
                && (leadSelectionIndex <= anchorSelectionIndex)))
        && (anchorSelectionIndex != -1 || leadSelectionIndex != -1))
      {
        // setting setLeadCalledFromAdd to true tells setLeadSelectionIndex
        //   not to update oldSel
        setLeadCalledFromAdd = true;
        setLeadSelectionIndex(index1);
        setLeadCalledFromAdd = false;
      }
    else
      {
        leadSelectionIndex = index1;
        anchorSelectionIndex = index0;
        sel.set(lo, hi+1);
        fireDifference(sel, (BitSet) oldSel);
      }
    }
  }


  /**
   * Deselects all indices in the inclusive range
   * <code>[index0,index1]</code>.
   *
   * @param index0 The beginning of the range of indices to deselect
   * @param index1 The end of the range of indices to deselect
   *
   * @see #addSelectionInterval
   * @see #setSelectionInterval
   */
  public void removeSelectionInterval(int index0,
                                      int index1)
  {
    if (index0 == -1 || index1 == -1)
      return;

    oldSel = sel.clone();
    int lo = Math.min(index0, index1);
    int hi = Math.max(index0, index1);

    // if selectionMode is SINGLE_INTERVAL_SELECTION and removing the interval
    //   (index0,index1) would leave two disjoint selection intervals, remove all
    //   selected indices from lo to the last selected index
    if (getMinSelectionIndex() > 0 && getMinSelectionIndex() < lo &&
        selectionMode == SINGLE_INTERVAL_SELECTION)
      hi = sel.size() - 1;

    sel.clear(lo, hi+1);
    //update anchorSelectionIndex and leadSelectionIndex variables
    //TODO: will probably need MouseDragged to test properly and know if this works
    setAnchorSelectionIndex(index0);
    leadSelectionIndex = index1;

    fireDifference(sel, (BitSet) oldSel);
  }

  /**
   * Removes all intervals in the selection set.
   */
  public void clearSelection()
  {
    // Find the selected interval.
    int from = sel.nextSetBit(0);
    if (from < 0)
      return; // Empty selection - nothing to do.
    int to = from;

    int i;

    for (i = from; i>=0; i=sel.nextSetBit(i+1))
      to = i;

    sel.clear();
    fireValueChanged(from, to, valueIsAdjusting);
  }

  /**
   * Fire the change event, covering the difference between the two sets.
   *
   * @param current the current set
   * @param x the previous set, the object will be reused.
   */
  private void fireDifference(BitSet current, BitSet x)
  {
    x.xor(current);
    int from = x.nextSetBit(0);
    if (from < 0)
      return; // No difference.
    int to = from;
    int i;

    for (i = from; i >= 0; i = x.nextSetBit(i+1))
      to = i;

    fireValueChanged(from, to, valueIsAdjusting);
  }

  /**
   * Clears the current selection and marks a given interval as "selected". If
   * the current selection mode is <code>SINGLE_SELECTION</code> only the
   * index <code>index2</code> is selected.
   *
   * @param anchor  the anchor selection index.
   * @param lead  the lead selection index.
   */
  public void setSelectionInterval(int anchor, int lead)
  {
    if (anchor == -1 || lead == -1)
      return;
    if (selectionMode == SINGLE_SELECTION)
      {
        int lo = lead;
        int hi = lead;
        int selected = sel.nextSetBit(0);
        if (selected == lead)
          return;  // the selection is not changing
        if (selected >= 0)
          {
            lo = Math.min(lo, selected);
            hi = Math.max(hi, selected);
          }
        if (anchorSelectionIndex >= 0)
          {
            lo = Math.min(lo, anchorSelectionIndex);
            hi = Math.max(hi, anchorSelectionIndex);
          }
        sel.clear();
        sel.set(lead);
        leadSelectionIndex = lead;
        anchorSelectionIndex = lead;
        fireValueChanged(lo, hi);
      }
    else if (selectionMode == SINGLE_INTERVAL_SELECTION)
      {
        // determine the current interval
        int first = sel.nextSetBit(0);
        int last = first;
        if (first >= 0)
          last += (sel.cardinality() - 1);

        // update the selection
        int lo = Math.min(anchor, lead);
        int hi = Math.max(anchor, lead);
        if (lo == first && hi == last)
          return;  // selected interval is not being changed
        sel.clear();
        sel.set(lo, hi + 1);

        // include the old selection in the event range
        if (first >= 0)
          lo = Math.min(lo, first);
        if (last >= 0)
          hi = Math.max(hi, last);
        if (anchorSelectionIndex >= 0)
          {
            lo = Math.min(lo, anchorSelectionIndex);
            hi = Math.max(hi, anchorSelectionIndex);
          }
        anchorSelectionIndex = anchor;
        leadSelectionIndex = lead;
        fireValueChanged(lo, hi);
      }
    else
    {
      BitSet oldSel = (BitSet) sel.clone();
      sel.clear();
      if (selectionMode == SINGLE_SELECTION)
        anchor = lead;

      int lo = Math.min(anchor, lead);
      int hi = Math.max(anchor, lead);
      sel.set(lo, hi+1);
      // update the anchorSelectionIndex and leadSelectionIndex variables
      setAnchorSelectionIndex(anchor);
      leadSelectionIndex = lead;

      fireDifference(sel, oldSel);
    }
  }

  /**
   * Inserts a number of indices either before or after a particular
   * position in the set of indices. Renumbers all indices after the
   * inserted range. The new indices in the inserted range are not
   * selected. This method is typically called to synchronize the selection
   * model with an inserted range of elements in a {@link ListModel}.
   *
   * @param index The position to insert indices at
   * @param length The number of indices to insert
   * @param before Indicates whether to insert the indices before the index
   *     or after it
   */
  public void insertIndexInterval(int index,
                                  int length,
                                  boolean before)
  {
    if (!before)
      {
        index++;
        length--;
      }
    BitSet tmp = sel.get(index, sel.size());
    sel.clear(index, sel.size());
    int n = tmp.size();
    for (int i = 0; i < n; ++i)
      sel.set(index + length + i, tmp.get(i));
  }

  /**
   * Removes a range from the set of indices. Renumbers all indices after
   * the removed range. This method is typically called to synchronize the
   * selection model with a deleted range of elements in a {@link
   * ListModel}.
   *
   * @param index0 The first index to remove (inclusive)
   * @param index1 The last index to remove (inclusive)
   */
  public void removeIndexInterval(int index0,
                                  int index1)
  {
    int lo = Math.min(index0, index1);
    int hi = Math.max(index0, index1);

    BitSet tmp = sel.get(hi, sel.size());
    sel.clear(lo, sel.size());
    int n = tmp.size();
    for (int i = 0; i < n; ++i)
      sel.set(lo + i, tmp.get(i));
  }

  /**
   * Fires a {@link ListSelectionEvent} to all the listeners of type {@link
   * ListSelectionListener} registered with this selection model to
   * indicate that a series of adjustment has just ended.
   *
   * The values of {@link #getMinSelectionIndex} and
   * {@link #getMaxSelectionIndex} are used in the {@link ListSelectionEvent}
   * that gets fired.
   *
   * @param isAdjusting <code>true</code> if this is the final change
   *     in a series of adjustments, <code>false/code> otherwise
   */
  protected void fireValueChanged(boolean isAdjusting)
  {
    fireValueChanged(getMinSelectionIndex(), getMaxSelectionIndex(),
                     isAdjusting);
  }

  /**
   * Fires a {@link ListSelectionEvent} to all the listeners of type {@link
   * ListSelectionListener} registered with this selection model.
   *
   * @param firstIndex The low index of the changed range
   * @param lastIndex The high index of the changed range
   */
  protected void fireValueChanged(int firstIndex, int lastIndex)
  {
    fireValueChanged(firstIndex, lastIndex, getValueIsAdjusting());
  }

  /**
   * Fires a {@link ListSelectionEvent} to all the listeners of type {@link
   * ListSelectionListener} registered with this selection model.
   *
   * @param firstIndex The low index of the changed range
   * @param lastIndex The high index of the changed range
   * @param isAdjusting Whether this change is part of a seqence of adjustments
   *     made to the selection, such as during interactive scrolling
   */
  protected void fireValueChanged(int firstIndex, int lastIndex,
                                  boolean isAdjusting)
  {
    ListSelectionEvent evt = new ListSelectionEvent(this, firstIndex,
                                                    lastIndex, isAdjusting);
    ListSelectionListener[] listeners = getListSelectionListeners();
    for (int i = 0; i < listeners.length; ++i)
      listeners[i].valueChanged(evt);
  }

  /**
   * Adds a listener.
   *
   * @param listener The listener to add
   *
   * @see #removeListSelectionListener
   * @see #getListSelectionListeners
   */
  public void addListSelectionListener(ListSelectionListener listener)
  {
    listenerList.add(ListSelectionListener.class, listener);
  }

  /**
   * Removes a registered listener.
   *
   * @param listener The listener to remove
   *
   * @see #addListSelectionListener
   * @see #getListSelectionListeners
   */
  public void removeListSelectionListener(ListSelectionListener listener)
  {
    listenerList.remove(ListSelectionListener.class, listener);
  }

  /**
   * Returns an array of all registerers listeners.
   *
   * @param listenerType The type of listener to retrieve
   *
   * @return The array
   *
   * @see #getListSelectionListeners
   * @since 1.3
   */
  public <T extends EventListener> T[] getListeners(Class<T> listenerType)
  {
    return listenerList.getListeners(listenerType);
  }

  /**
   * Returns an array of all registerd list selection listeners.
   *
   * @return the array
   *
   * @see #addListSelectionListener
   * @see #removeListSelectionListener
   * @see #getListeners
   * @since 1.4
   */
  public ListSelectionListener[] getListSelectionListeners()
  {
    return (ListSelectionListener[]) getListeners(ListSelectionListener.class);
  }

  /**
   * Returns a clone of this object.
   * <code>listenerList</code> don't gets duplicated.
   *
   * @return the cloned object
   *
   * @throws CloneNotSupportedException if an error occurs
   */
  public Object clone()
    throws CloneNotSupportedException
  {
    DefaultListSelectionModel model =
      (DefaultListSelectionModel) super.clone();
    model.sel = (BitSet) sel.clone();
    model.listenerList = new EventListenerList();
    return model;
  }
}