Java开发网 - 一个类被声明为protected意味着什么？

Topic: 一个类被声明为protected意味着什么？

1.一个类被声明为protected意味着什么？	Copy to clipboard
Posted by: jacksun Posted on: 2003-03-18 16:25 RT。另外，如果该声明为"protected"的类包含一些"abstract"的方法，那么"abstract"表示什么意思？可参考的文档如下： http://myhome.naver.com/pumila/doc/java.midp.siemens/com/siemens/mp/game/GraphicObject.html

2.Re:一个类被声明为protected意味着什么？ [Re: jacksun]

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Posted by: snowbug
Posted on: 2003-03-18 23:10

It seems that the class itself is still public while the constructor is protected. A protected constructor means that the class can not be directly instanciated but it can be accessed from the constructor of its sub-classes (as oppose to private constructor, which can not be accessed from the sub-classes).

The abstract keyword means that those methods are not implemented in the class and the sub class must provide a concrete implemenation if unless the sub-class is also declared abstract.

3.Re:一个类被声明为protected意味着什么？ [Re: jacksun]	Copy to clipboard
Posted by: jacksun Posted on: 2003-03-19 00:07 I got it. Thanks snowbug! But is it appropriate for a class contains an abstract method? It is supposed every method reside in a class should be implemented. I don't know whether it is correct to say that only interface and abstract class contains abstract method. Best regards.

4.Re:一个类被声明为protected意味着什么？ [Re: jacksun]	Copy to clipboard
Posted by: Tormz Posted on: 2003-03-19 13:17 Can a class be declare protect? only the field or the member method can be specify protect~

5.Re:一个类被声明为protected意味着什么？ [Re: Tormz]	Copy to clipboard
Posted by: learner Posted on: 2003-03-20 04:46 Tormz wrote: Can a class be declare protect? only the field or the member method can be specify protect~ A class can only have "public" or default modifier, except inner classes - which can also have "private" and "protected".

6.Re:一个类被声明为protected意味着什么？ [Re: jacksun]

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Posted by: learner
Posted on: 2003-03-20 04:53

jacksun wrote:
I got it. Thanks snowbug!

But is it appropriate for a class contains an abstract method? It is supposed every method reside in a class should be implemented. I don't know whether it is correct to say that only interface and abstract class contains abstract method.

Best regards.

A class must be declared abstract when it:
- has abstract method( s )
- is a subclass of another class that has abstract method( s ), which itself does not provide the implementation
- implements an interface that has abstract method( s ), which itself does not provide the implementation

7.Re:一个类被声明为protected意味着什么？ [Re: jacksun]	Copy to clipboard
Posted by: xiaopan Posted on: 2003-03-22 15:55 （缩略图，点击图片链接看原图）