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//========================================================================
//Copyright 2007-2010 David Yu [email protected]
//------------------------------------------------------------------------
//Licensed under the Apache License, Version 2.0 (the "License");
//you may not use this file except in compliance with the License.
//You may obtain a copy of the License at
//http://www.apache.org/licenses/LICENSE-2.0
//Unless required by applicable law or agreed to in writing, software
//distributed under the License is distributed on an "AS IS" BASIS,
//WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//See the License for the specific language governing permissions and
//limitations under the License.
//========================================================================
package com.dyuproject.protostuff.parser;
/**
* An entity whose values can be overriden with new value.
* It can also be reset to its initial state.
*
* @author David Yu
* @created May 10, 2010
*/
public class Mutable
{
private T current, last;
public Mutable(T value)
{
if(value == null)
throw new IllegalArgumentException("The arg 'value' cannot be null.");
current = value;
}
public void override(T newValue)
{
// can only override once.
// needs to be reset before it can be overriden again.
if(last == null)
{
last = current;
current = newValue;
}
}
public void reset()
{
if(last != null)
{
current = last;
last = null;
}
}
public T getValue()
{
return current;
}
public T getLast()
{
return last;
}
public boolean isOverridden()
{
return last != null;
}
}