说明：  工厂模式有：简单工厂模式；工厂方法模式；抽象工厂模式。抽象的程度越来越强，给出了三种模式的java代码，想完全理解还要仔细研究。
(Factory pattern: simple factory pattern factory method model abstract factory pattern. Growing degree of abstraction is given three kinds of models java code, and would like to fully understand but also careful study.)