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parser for .proto files

There is a newer version: 3.1.40

//========================================================================
//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 io.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;
    }

}