How to count duplicate values in the list object in Java? [duplicate]

Question

in java, i have an array like this:

String[] city = {"texas", "ny", "sydney", "ny", "paris", "texas", "ny"};

i want to sort/group them with count...like-

texas = 2
ny = 3
sydney = 1
paris = 1

Have you tried anything at all? (Helpful links for asking better questions: How to Ask, FAQ) — tckmn
– tckmn, Commented Mar 28, 2013 at 12:30

AmitG · Accepted Answer · 2013-03-28 13:22:48Z

10

Use Collections.frequency() method.

import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Test{
    public static void main(String[] args) {
        String[] city = {"texas", "ny", "sydney", "ny", "paris", "texas", "ny"};
        List<String> asList = Arrays.asList(city);
        Map<String, Integer> map= new HashMap<String, Integer>();
        for(String s: city){
            map.put(s,Collections.frequency(asList,s));
        }
        System.out.println(map);

    }
}

edited Mar 28, 2013 at 13:22

answered Mar 28, 2013 at 12:41

AmitG

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1 Comment

tmwanik Over a year ago

+1 for Collections#frequency(java.util.Collection, Object)

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