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# multi elements in a set.

meow00 asked
on
Medium Priority
362 Views
Last Modified: 2010-10-05
Hello experts,

Can I have one elements to appear several times in a set ? if not, how do I do it ?

thanks.
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Top Expert 2016

Commented:
No - use a LIst
Java Developer
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Top Expert 2010

Commented:
not if the elements are equals

you need to use a different collection, such as a List
Java Developer
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Top Expert 2010

Commented:
Sets are for containing uniqueue elements, ie. no duplicates

what is it u are trying to achieve?
Java Developer
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Top Expert 2010

Commented:
If you see here, it explains what a Set is used for

http://java.sun.com/docs/books/tutorial/collections/interfaces/set.html

Have a look thru here to determine the type of Collection that best suits your needs:

http://java.sun.com/docs/books/tutorial/collections/interfaces/index.html

Commented:
So I have two collections:

list1 = "A", "A", "B", "C", "C"
and
list2 = "C", "A", "A", "C","B"

if the order I added to the list are different ...
how do I check if they are the same ( ps. I need the above to list to be EQUAL) ... can list do that ?

thanks.
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Top Expert 2016
Commented:
sort them first then apply list1.equals(list2)

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Java Developer
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Top Expert 2010

Commented:
use an ArrayList and first sort them
Java Developer
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Top Expert 2010

Commented:
Collections.sort(list1);
Collections.sort(list2);
if (list1.equals(list2))
{
...
Java Developer
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Top Expert 2010
Commented:
you couls also use the List's containsAll() method

Commented:
Add a new class with weight value
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