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Collection VS ArrayList.

Suresh Rajadurai
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Joined: Feb 22, 2007
Posts: 58
Hi Folks,

I compiled the following 2 java programs, the first one gives compilation error, the 2nd one compiles fine.
The first program, the compiler does not recognize the command "Collections.sort(s)". Could anyone please throw some light on it please.

Program 1:




Program 2:




Thanks in advance.

Suresh
Dawn Charangat
Ranch Hand

Joined: Apr 26, 2007
Posts: 249
Hello Suresh..,

The sort() method in Collections utility class takes in only objects of the type "List". Just since
the List interface extends from Collection interface doesn't mean you can directly cast it into the method.
May be this could help solve your confusion.

Dawn
Paul Beckett
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Joined: Jun 14, 2008
Posts: 96
The reason the sort method is applied to a List and not just any Collection is because not all Collection implementations are ordered.

Lists are ordered, that iteration over the elements is guaranteed to return them in a consistent order.

Sets are unordered, that is iteration over the elements is not guaranteed to return them in a consistent order.
Suresh Rajadurai
Ranch Hand

Joined: Feb 22, 2007
Posts: 58
Hi Paul , Dawn,

Thank you so much for the beautiful explanation. Much appreciated.


Regards

Suresh.
 
 
subject: Collection VS ArrayList.