| /******************************************************************************* |
| * Copyright (c) 2006 Sybase, Inc. and others. |
| * |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/epl-v10.html |
| * |
| * Contributors: |
| * Sybase, Inc. - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.jst.pagedesigner.jsp.core; |
| |
| /** |
| * Local version of org.eclipse.jface.util.ListenerList (modified) |
| * @author mengbo |
| * @version 1.5 |
| */ |
| public class ListenerList { |
| /** |
| * The current number of listeners. Maintains invariant: 0 <= fSize <= |
| * listeners.length. |
| */ |
| private int _size; |
| |
| /** |
| * The list of listeners. Initially <code>null</code> but initialized to |
| * an array of size capacity the first time a listener is added. Maintains |
| * invariant: listeners != null if and only if fSize != 0 |
| */ |
| private Object[] _listeners = null; |
| |
| /** |
| * The empty array singleton instance, returned by getListeners() when size == |
| * 0. |
| */ |
| private static final Object[] EmptyArray = new Object[0]; |
| |
| /** |
| * Creates a listener list with the given initial capacity. |
| * |
| * @param capacity |
| * the number of listeners which this list can initially accept |
| * without growing its internal representation; must be at least |
| * 1 |
| */ |
| public ListenerList(int capacity) { |
| if (capacity < 1) { |
| throw new IllegalArgumentException(); |
| } |
| _listeners = new Object[capacity]; |
| _size = 0; |
| } |
| |
| /** |
| * Adds a listener to the list. Has no effect if an identical listener is |
| * already registered. |
| * |
| * @param listener |
| * a listener |
| */ |
| public synchronized void add(Object listener) { |
| if (listener == null) { |
| throw new IllegalArgumentException(); |
| } |
| // check for duplicates using identity |
| for (int i = 0; i < _size; ++i) { |
| if (_listeners[i] == listener) { |
| return; |
| } |
| } |
| // grow array if necessary |
| if (_size == _listeners.length) { |
| Object[] temp = new Object[(_size * 2) + 1]; |
| System.arraycopy(_listeners, 0, temp, 0, _size); |
| _listeners = temp; |
| } |
| _listeners[_size++] = listener; |
| } |
| |
| /** |
| * Returns an array containing all the registered listeners. The resulting |
| * array is unaffected by subsequent adds or removes. If there are no |
| * listeners registered, the result is an empty array singleton instance (no |
| * garbage is created). Use this method when notifying listeners, so that |
| * any modifications to the listener list during the notification will have |
| * no effect on the notification itself. |
| * @return the array of registered listeners |
| */ |
| public synchronized Object[] getListeners() { |
| if (_size == 0) { |
| return EmptyArray; |
| } |
| Object[] result = new Object[_size]; |
| System.arraycopy(_listeners, 0, result, 0, _size); |
| return result; |
| } |
| |
| /** |
| * Removes a listener from the list. Has no effect if an identical listener |
| * was not already registered. |
| * |
| * @param listener |
| * a listener |
| */ |
| public synchronized void remove(Object listener) { |
| if (listener == null) { |
| throw new IllegalArgumentException(); |
| } |
| |
| for (int i = 0; i < _size; ++i) { |
| if (_listeners[i] == listener) { |
| if (--_size == 0) { |
| _listeners = new Object[1]; |
| } else { |
| if (i < _size) { |
| _listeners[i] = _listeners[_size]; |
| } |
| _listeners[_size] = null; |
| } |
| return; |
| } |
| } |
| } |
| |
| /** |
| * Removes all the listeners from the list. |
| */ |
| public void removeAll() { |
| _listeners = new Object[0]; |
| _size = 0; |
| } |
| |
| /** |
| * Returns the number of registered listeners |
| * |
| * @return the number of registered listeners |
| */ |
| public int size() { |
| return _size; |
| } |
| } |