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Collection

preeti khane
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Joined: Mar 12, 2003
Posts: 93
Which of these statements concerning the collection interfaces are true?
1) Set extends Collection.
2) All methods defined in Set are also defined in Collection.
3) List extends Collection.
4) All methods defined in List are also defined in Collection.
5) Map extends Collection.
Answer is 1,2,3
I thought it was 1,2
I mean if Set extends then how can evrything in Set be defined in Collecion
Manish Hatwalne
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Joined: Sep 22, 2001
Posts: 2578

Originally posted by preeti khane:
Which of these statements concerning the collection interfaces are true?
1) Set extends Collection.
2) All methods defined in Set are also defined in Collection.
3) List extends Collection.
4) All methods defined in List are also defined in Collection.
5) Map extends Collection.
Answer is 1,2,3
I thought it was 1,2
I mean if Set extends then how can evrything in Set be defined in Collecion

I think, you meant you thought 1 and 3 were correct.
As for Set, it contains no methods of its own, all its methods are inherited from Collection, hence 2 is correct.
HTH,
- Manish
preeti khane
Ranch Hand

Joined: Mar 12, 2003
Posts: 93
manish,
yes I meant 1,3
I see now , Set is an interface with no methods of its own.. kept thinking it was a concrete implementation... duh!!
thanks
Pallavi Chakraborty
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Joined: Jan 18, 2003
Posts: 93
Hey everybody,
What about option 4 ?
Pallavi
Rattan Mann
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Joined: Jan 21, 2003
Posts: 44
Map does not extend Collection.Collection is a set of elements but map is a key-value pair. So Map and SortedMap (which extends Map)form a group of their own. Finally, HashMap implements Map.
Rattan
Rattan Mann
Ranch Hand

Joined: Jan 21, 2003
Posts: 44
Map does not extend Collection.Collection is a set of elements but map is a key-value pair. So Map and SortedMap (which extends Map)form a group of their own. Finally, HashMap implements Map.
Rattan
Monisha Talwar
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Joined: Feb 11, 2003
Posts: 102
What about list? Does it have its own methods? Besides what it gets from Collection?


Hey! It compiles! Ship it!
William Brogden
Author and all-around good cowpoke
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Joined: Mar 22, 2000
Posts: 12675
    
    5
Thats the kind of question you should be answering by referring to the JavaDocs for the java.util package.
Bill
Rattan Mann
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Joined: Jan 21, 2003
Posts: 44
As Bill says, this can be found out easily from APIs and docs. Moreover, set having no more methods than collection is more of an exception than a rule. In general, if there are no more (behaviour-specific) methods in subinterfaces then what is the point of extension! List definitely has more methods which are list-specific.
Rattan
 
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