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A question about abstract classes

jayram
Ranch Hand

Joined: Oct 30, 2000
Posts: 94
hello!!!
This is about abstract classes.From whatever I have learnt till now abstract classes can not be instantiated.But if we look at URL class it has got a method url.openConnection() which according to jdk documentation

"Returns a URLConnection object that represents a connection to the remote object referred to by the URL. "
Now URLConnection class as per my knowledge is an abstract class...so whats the magic in openConnection method which causes instantiation of an abstract class.
Please correct me if i am wrong...

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Cheers
Jayram
Paul Anilprem
Enthuware Software Support
Ranch Hand

Joined: Sep 23, 2000
Posts: 3253
    
    2
There is no magic. What happens when you do, hashtable.keys() ? It returns an Enumeration. But Enumeration is an interface!! How can it instantiate an interface?
In all such cases, the method returns an object of either a class that implements the interface or a class that extends from the abstract class... as the case may be.
You can actually try this:
Enumeration enum = hashtable.keys();
System.out.println( enum.getClass());
HTH,
-Paul.


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