how to find number of same value in a array list using java

Question

I have array list with value like

In above list,it has value 125 for 4 time I have the value 125 from another and i can check whether list having 125 or not. But not able to find how many times it occur or present in list

How about adding the code you already have to check whether the number is present or not? Hints can flow from there — Pablo, Sep 30 '13 at 07:08
Here it is http://stackoverflow.com/questions/505928/how-to-count-occurrence-of-an-element-in-a-list — Balaji Dhanasekar, Sep 30 '13 at 07:12

score 11 · Answer 1 · edited Sep 30 '13 at 07:14

11

Use Collections#frequency() method:

List<Integer> list = Arrays.asList(125, 154, 166, 125, 125, 222, 125);
int totalCount = Collections.frequency(list, 125);

edited Sep 30 '13 at 07:14

Bohemian

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answered Sep 30 '13 at 07:09

Rohit Jain

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+1 don't reinvent the wheel! – Bohemian Sep 30 '13 at 07:13

Subhrajyoti Majumder · Answer 2 · 2013-09-30T07:14:06.933

2

You can use Guava libraries Multiset, elements of a Multiset that are equal to one another are referred to as occurrences of the same single element.

Multiset<Integer> myMultiset = HashMultiset.create();
myMultiset.addAll(list);
System.out.println(myMultiset.count(125)); // 4

edited Sep 30 '13 at 07:14

answered Sep 30 '13 at 07:09

Subhrajyoti Majumder

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score 1 · Answer 3 · answered Sep 30 '13 at 07:12

1

List<Integer> list = Arrays.asList(125,154,166,125,125,222,125);

int count = Collections.frequency(list, 125);

System.out.println("total count: " + tcount);

Output:

total count: 4

answered Sep 30 '13 at 07:12

Maxim Shoustin

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score 1 · Answer 4 · answered Sep 30 '13 at 07:20

Also possible to map it into a map. Bit more code though:

package com.stackoverflow.counter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Count {
    public Map<Integer,Integer> convertToMap(List<Integer> integerList) {
        Map<Integer,Integer> integerMap = new HashMap<>();
        for (Integer i: integerList) {
            Integer numberOfOccurrences = integerMap.get(i);
            if (numberOfOccurrences == null)
                numberOfOccurrences = 0;
            integerMap.put(i,++numberOfOccurrences);
        }
        return integerMap;
    }
    public static void main(String[] args) {
        List<Integer> integerList = new ArrayList<>();
        integerList.add(1);
        integerList.add(3);
        integerList.add(2);
        integerList.add(1);
        integerList.add(3);
        integerList.add(2);
        integerList.add(4);
        integerList.add(5);
        integerList.add(5);
        Count count = new Count();
        Map<Integer, Integer> integerMap = count.convertToMap(integerList);
        for (Integer i: integerMap.keySet()) {
            System.out.println("Number: " + i + ", found " + integerMap.get(i) + " times.");
        }
    }
}

how to find number of same value in a array list using java

4 Answers4