Re: [List handling]number of occurences

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.help

Date:

Fri, 27 Jul 2007 09:10:36 -0700

Message-ID:

<f8d5e0$j08$1@ihnp4.ucsd.edu>

Daniel Moyne wrote:

I have this type of list :
private static ArrayList<String> firstJurisdictionInPlace=new
ArrayList<String>();
private static Collator myCollator;
firstJurisdictionInPlace.removeAll(firstJurisdictionInPlace);
if (_place.equals(my_PLAC)) {
        if (!firstJurisdictionInPlace.contains(firstJurisdiction)) {
                firstJurisdictionInPlace.add(firstJurisdiction);
                firstJurisdictionCount+=1;
                }
        }
}
/* we sort alphabetically all lieux-dits */
Collections.sort(firstJurisdictionInPlace,myCollator);

So basically I update my list with a new "firstJurisdiction" each time
the "if condition" is true ; besides I count the number of entries in my
list ; it works fine.

When I meet a "firstJurisdiction" already in the list I do nothing but now I
want to count the number of occurences of each entry of my list by doing
something like this :
        if (!firstJurisdictionInPlace.contains(firstJurisdiction)) {
                firstJurisdictionInPlace.add(firstJurisdiction);
                firstJurisdictionCount+=1;
                }
        }
        else {
                _count_for_this_jurisdictio+=1;
                ......
        }

How to manage this for me to be able to retrieve the number of occurences of
each item of my list ; I would like to avoid using typical array as here I
do not care about dimension of my list.

Thanks.

If, at any given time, you want the count for a particular value, and
the list may change before you need another:

int count = 0;
for(String fj: firstJurisdictionInPlace){
   if(fj.equals(firstJurisdiction)){
     count++;
   }
}

If you need many or all of the counts for the same value of the list,
use a similar loop but maintaining a map with a counter for each value.

Patricia