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;
        }

    }
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
protostuff-parser/src/main/java/io/protostuff/parser/Mutable.java