问题描述
我是JAVA的新手，刚刚开始学习IS-A和HAS-A关系，但却无法获得太多。我想想象一下这两者是如何不同的以及我们何时应该使用IS-A和HAS-A？
I am new to JAVA and just started learning IS-A and HAS-A relation but couldn't get much .I want to visualize how these two are different and when we should be using IS-A and HAS-A ?
推荐答案
IS-A关系是遗产。继承的类称为子类或子类。另一方面，HAS - A关系是组合
An IS-A relationship is inheritances. The classes which inherit are known as sub classes or child classes. On the other hand, HAS - A relationship is composition
在OOP中，IS - 关系是完全继承的。这意味着，子类是一种父类。例如，苹果是一种水果。所以你会扩展水果以获得苹果。
In OOP, IS - A relationship is completely inheritance. This means, that the child class is a type of parent class. For example, an apple is a fruit. So you will extend fruit to get apple.
class Apple extends Fruit{
.
.
}
另一方面，组合意味着创建具有对其他对象的引用的实例。例如，一个房间有一张桌子。
所以你将创建一个教室，然后在该类中创建一个类型表的实例。
On the other hand, composition means creating instances which have references to other objects. For example, a room has a table.So you will create a class room and then in that class create an instance of type table.
class Room{
:
Table table = new Table ();
:
:
}
HAS-A关系是动态（运行时）绑定，而继承是静态（编译时）绑定。
如果您只是想重用代码，并且您知道两者不是同一类，请使用组合。例如，你不能从厨房烤箱。厨房有一个烤箱。
当你觉得像Apple这样的自然关系是Fruit使用继承。
A HAS-A relationship is dynamic (run time ) binding while inheritance is a static (compile time ) binding.If you just want to reuse the code and you know that the two are not of same kind use composition. For example, you cannot an oven from a kitchen. A kitchen HAS-A oven.When you feel there is a natural relationship like Apple is a Fruit use inheritance.
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