public ArrayList<Value> getUniqueSortedValues()
    {
        if (uniqueSortedValues != null)
            return uniqueSortedValues;

        uniqueSortedValues = new ArrayList<Value>();
        Value last = null;
        for (Value v : sortedValues)
        {
            if (last == null || v.number != last.number)
                uniqueSortedValues.add(v);
            last = v;
        }
        return uniqueSortedValues;
    }
Disabled by default (the earlier protoc 2.x versions enabled this by default, but was changed later on).
protostuff-parser/src/main/java/io/protostuff/parser/EnumGroup.java