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Set question

Arad Chear
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Joined: Jan 05, 2007
Posts: 98


since Double is-a Number
Keith Lynn
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Joined: Feb 07, 2005
Posts: 2367
Yes, Double is a Number. But the elements of a TreeSet have to be mutually comparable.
Arad Chear
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Joined: Jan 05, 2007
Posts: 98
thanks so much lynn ,i got it
m ali
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Joined: Apr 12, 2007
Posts: 49
Hi Keith,

But we are declaring here the collection as type-safe number. Integer is a Number and Double is a Number? Why the above code fail to compile? please explain?

Thanks in advance.
Chandra Bhatt
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Joined: Feb 28, 2007
Posts: 1707


No, Ali, Did you compile the above code?
This code compiles fine but gives runtime exception because
of mutual incomparability between treeset objects. One object
is Integer and another is Double.

TreeSet uses Comparable interface's compareTo(...) method that
is implemented by the objects inserted into, tokeep the objects
in sorted manner. And an Integer and an Double can't be compared
because they are not mutually comparable as Keith said
already.




Regards,
cmbhatt
[ April 24, 2007: Message edited by: Chandra Bhatt ]

cmbhatt
m ali
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Joined: Apr 12, 2007
Posts: 49
Thank you Chandra,

I got it.
Zhao zhenhua
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Joined: Jul 17, 2006
Posts: 37

Thanks ,Chandra Bhatt.Yes!You are right!


Head first Servlet and JSP
 
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subject: Set question