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extending two classes from a single class

 
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extending two classes from a single class
nila
post 3 Jul, 2008 - 01:50 AM
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Hi,
I need to extend two classes from a single class.How can i do this in a servlet

like
A class OutboundServlet extends HttpServlet should also extends AbstractManagerEventListener.How can i do this?
please assist me.

Thanks.
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Programmist
post 3 Jul, 2008 - 02:54 AM
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You can't. Java allows only single class inheritance. Classes can, however, implement multiple interfaces.

This post has been edited by Programmist: 3 Jul, 2008 - 02:54 AM
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nila
post 3 Jul, 2008 - 03:00 AM
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Is there any other way to do this?
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baavgai
post 3 Jul, 2008 - 03:16 AM
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The way to do it is to write a "wrapper" class that holds objects of the type you wanted to multi inherit and exposes the methods you want from the two classes.

As stated, you can only extend one class, but implement multiple interfaces. For extra OO goodness, you can make an interface to each of the two classes and have your third class implement both. This will essentially give you the functionality you'd get from fusing the things together, anyway.
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nila
post 3 Jul, 2008 - 03:53 AM
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how can i make an interface for a class?
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JeroenFM
post 3 Jul, 2008 - 04:06 AM
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QUOTE(nila @ 3 Jul, 2008 - 03:53 AM) *

how can i make an interface for a class?


I believe the following should explain a few things

http://java.sun.com/docs/books/tutorial/ja.../interface.html
http://java.sun.com/docs/books/tutorial/ja...einterface.html
http://java.sun.com/docs/books/tutorial/ja...subclasses.html
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nila
post 3 Jul, 2008 - 10:43 PM
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How can i create a concrete class for an abstract class using reflection.please show me in code.

Thanks
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JeroenFM
post 4 Jul, 2008 - 01:47 AM
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QUOTE(nila @ 3 Jul, 2008 - 10:43 PM) *

How can i create a concrete class for an abstract class using reflection.please show me in code.

Thanks


Short answer: You can't

Long answer: Due to the ClassLoader mechanism you can't determine possible subclasses for a given class since there is no way of knowing all existing classes or obtaining them, and the java.lang.Class class therefore has no "getSubClasses" method. So using reflection, you can not determine concrete classes for an abstract class.
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