Re: Counting char Occurences in ArrayList

From:

Richard Reynolds <richiereynolds@ntlworld.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 12 Mar 2008 21:38:10 GMT

Message-ID:

<v3pjyfkz3a31$.wqz9bma51igi$.dlg@40tude.net>

On Wed, 12 Mar 2008 12:55:33 -0700 (PDT), mnml wrote:

Hi,
I have some char stored in an ArrayList, I would like to know if there
is a way to
count the occurences of each of these char and return the one that
occurs the most.
Thanks

lots of ways, here's one that's easy to understand -

import java.util.*;

public class Oi
{
    public static void main(String[] args)
    {
        List<Character> l = new ArrayList<Character>();
        l.add('c');
        l.add('l');
        l.add('h');
        l.add('l');

        if(!l.isEmpty())
        {
            int maxOccurrences = 0;
            char mode = '0';

            Map<Character, Integer> m = new HashMap<Character, Integer>();

            for(char c : l)
            {
                m.put(c, m.get(c) == null ? 1 : m.get(c) + 1);
            }

            for(char c : m.keySet())
            {
                if(m.get(c) > maxOccurrences)
                {
                    maxOccurrences = m.get(c);
                    mode = c;
                }
                System.out.println(c + ":" + m.get(c));
            }
            System.out.println("Most frequent was " + mode +
                              " with " + maxOccurrences + " occurrences.");
        }
    }
}