英文:
Question about Abstract Classes when classes are nested
问题
如果ClassB被声明为abstract因为它包含抽象方法，那么ClassA是否也必须被声明为Abstract？
英文:
So let's say ClassB is a class defined inside ClassA (Nested Classes), my question is, if ClassB is declared abstract as it contains abstract Methods, would ClassA also have to be declared Abstract ?
答案1
得分: 1
No. 每个类的方法属于它自己。一个类不拥有其他嵌套在其中的类（或接口！）的方法，并且包含嵌套抽象类或嵌套接口不要求容器类是抽象的。
英文:
No. The methods of each class are its own. A class does not own the methods of other classes (or interfaces!) nested within, and containing a nested abstract class or a nested interface does not require the container class to be abstract.
答案2
得分: 1
不，它并不会。无论外部类还是父类是否为abstract，在Java中都没有强制要求类是abstract的规定。
一个例子：
class classA {
abstract class classB { // 也可以是静态的
abstract void foo();
}
}
另一方面，方法略有不同：abstract方法必须只能放在abstract类或接口（隐式抽象）中。
英文:
Nope, it doesn't. It doesn't matter whether the outer or parent class is abstract, there is no rule in Java enforcing a class being abstract.
An example:
class classA {
abstract class classB { // can also be static
abstract void foo();
}
}
On the other hand, it's a bit different with the methods: abstract methods must be placed only inside the abstract classes or interfaces (implicitely abstract).
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