As usual, constructors are different from other kinds of methods. This is also true when polymorphism is involved. Even though constructors are not polymorphic(they‘re actually static methods, but the static declaration is implicit), it‘s important to understand the way constructors work in complex hierarchies and with polymorphism. This understanding will help you avoid unpleasant entanglements.
Java:Constructors and polymorphism
原文：http://www.cnblogs.com/taoxiuxia/p/4456571.html