MapChanges.java

/*
 * MapChanges.java
 * Copyright 2008 (C) James Dempsey
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Created on 19/09/2008 08:49:44
 *
 * $Id: $
 */
package pcgen.rules.context;

import java.util.Map;


/**
 * The Class {@code MapChanges} is responsible for tracking changes to
 * a map so that the changes can be committed or rolled back at a later 
 * stage. Items can be added to the map, removed from the map or the map 
 * can be cleared.
 * 
 * 
 * @author James Dempsey <jdempsey@users.sourceforge.net>
 */
public class MapChanges<K, V>
{
	private final Map<K, V> positive;
	private final Map<K, V> negative;
	private final boolean clear;

	/**
	 * Instantiates a new map changes object.
	 * 
	 * @param added the map of items added
	 * @param removed the map of items removed
	 * @param globallyCleared has the map been cleared
	 */
	public MapChanges(Map<K, V> added, Map<K, V> removed,
		boolean globallyCleared)
	{
		positive = added;
		negative = removed;
		clear = globallyCleared;
	}

	/**
	 * Includes global clear.
	 * 
	 * @return true, if the map was cleared
	 */
	public boolean includesGlobalClear()
	{
		return clear;
	}

	/**
	 * Checks if the change set is empty.
	 * 
	 * @return true, if is empty
	 */
	public boolean isEmpty()
	{
		return !clear && !hasAddedItems() && !hasRemovedItems();
	}

	/**
	 * Gets the map of added items.
	 * 
	 * @return the added items
	 */
	public Map<K, V> getAdded()
	{
		return positive;
	}

	/**
	 * Checks for added items.
	 * 
	 * @return true, if there are items to add
	 */
	public boolean hasAddedItems()
	{
		return positive != null && !positive.isEmpty();
	}

	/**
	 * Gets the map of removed items.
	 * 
	 * @return the removed items
	 */
	public Map<K, V> getRemoved()
	{
		return negative;
	}

	/**
	 * Checks for removed items.
	 * 
	 * @return true, if there are items to remove
	 */
	public boolean hasRemovedItems()
	{
		return negative != null && !negative.isEmpty();
	}
}