问一个java语言规范纯理论问题
无名老僧 2012-06-12 03:18:20 A variable of an interface type can hold a null reference or a reference to any
instance of any class that implements the interface.
Note that a variable is not guaranteed to always refer to a subtype of its declared type, but
only to subclasses or subinterfaces of the declared type. This is due to the possibility of
heap pollution discussed below.
------The Java™ Language Specification Java SE 7 Edition 第4章 4.12.2
请问上面讲到的subtype 跟subclass,subinterface分别指的是什么?