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ComparingPair.java
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ComparingPair.java
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/*
* Copyright 2013, Red Hat, Inc. and individual contributors as indicated by the
* @author tags. See the copyright.txt file in the distribution for a full
* listing of individual contributors.
*
* This 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 software 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 software; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA, or see the FSF
* site: http://www.fsf.org.
*/
package org.zanata.webtrans.client.presenter;
import org.zanata.webtrans.shared.model.TransHistoryItem;
/**
* This class holds two distinct translation history items at most. They are then used for comparison.
* The object created is immutable. See test for more detail.
*
* @author Patrick Huang <a href="mailto:pahuang@redhat.com">pahuang@redhat.com</a>
*/
class ComparingPair
{
private final TransHistoryItem one;
private final TransHistoryItem two;
private ComparingPair(TransHistoryItem one, TransHistoryItem two)
{
this.one = one;
this.two = two;
}
public static ComparingPair empty()
{
return new ComparingPair(null, null);
}
TransHistoryItem one()
{
return one;
}
TransHistoryItem two()
{
return two;
}
/**
* Add item to this holder.
* If item already exist in this holder, it will be removed.
* If current holder is full (already contains two items), new item won't be added in. i.e. no op.
* Otherwise it will be added to the holder.
*
* @param newItem to be added/removed item
* @return a new object of this class
*/
public ComparingPair addOrRemove(TransHistoryItem newItem)
{
if (isEmpty())
{
return new ComparingPair(newItem, null);
}
if (newItem == one)
{
return new ComparingPair(two, null);
}
if (newItem == two)
{
return new ComparingPair(one, null);
}
if (isFull())
{
return this;
}
return new ComparingPair(one, newItem);
}
private boolean isEmpty()
{
return one == null && two == null;
}
public boolean isFull()
{
return one != null && two != null;
}
public boolean contains(TransHistoryItem item)
{
return one == item || two == item;
}
}