Java：has a ; is a意义

题目

Java：has a ; is a意义
1． Which statement is true about has-a and is-a relationships?A
A.Inheritance represents an is-a relationship.
B.Inheritance represents a has-a relationship.
C.Interfaces must be use when creating a has-a relationship.
D.Instance variables must be used when creating an is-a relationship.
这道题中的has-a和is-a是什么意思?

答案

has-a 有一个, is-a 是一个.
比如继承 ,有一个图形类和一个圆形类,圆形类继承于图形类.可以说圆形是一个图形,就是is-a的意思.
比如组合,一个汽车类和一个轮子类,汽车有轮子,就是has-a的意思.