Architecture is full of examples of items designed to do more than one thing. Your smart phone is a flash light. From my last examples, a chair is also a clothes hanger. A seat cushion is a flotation device.
Robert Martin said in his book Agile Software Development, Principles, Patterns, and Practice (http://en.wikipedia.org/wiki/Robert_Cecil_Martin), that every class should have a single responsibility over a part of the function. The function-part should be encapsulated and the class should do that and only that.