Display words in decreasing order of their occurance

Question

I have to count the occurrences of words and display them by number of occurrences (in decreasing order). I can count the words but don't know how to proceed further. It may be I'm not doing it efficiently. If possible please suggest a solution.

import java.io.*;
import java.util.*;

public class MaxOccurence
{
    public static void main(String[] args)
    {
        Map<String, Integer> map = new HashMap<>();
        try
        {
            BufferedReader br = new BufferedReader(new FileReader(new File(
                "F:/Demo/file_reading/bin/demo/hello.txt")));
            String str;
            while ((str = br.readLine()) != null)
            {
                Scanner sc = new Scanner(str);
                while (sc.hasNext())
                {
                    String word = sc.next();
                    if (map.containsKey(word))
                        map.put(word, map.get(word) + 1);
                    else
                        map.put(word, 1);
                }
            }
            System.out.println("yes");
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        System.out.println(map);
    }
}

score 1 · Accepted Answer · answered Apr 17 '15 at 22:12

I think your approach of using the HashMap class with map.containsKey method is an efficient approach for the word count you solved so what is left is to order and print the map in a descending order, here is a clean and efficient example on how to achieve this:

map.entrySet().stream()
          .sorted(Collections.reverseOrder(Map.Entry.comparingByValue()))
          .forEachOrdered(System.out::println);

Note that if you remove the Collection.reverseOrder call the order will be ascending.

Adding this to your code will look like this:

import java.io.*;
import java.util.*;
import java.util.stream.*;

public class MaxOccurence {

  public static void main(String[] args) {

    Map<String, Integer> map = new HashMap<>();
    try {
        BufferedReader br = new BufferedReader(new FileReader(new File(
                "F:/Demo/file_reading/bin/demo/hello.txt")));
        String str;
        while ((str = br.readLine()) != null) {
            Scanner sc = new Scanner(str);
            while (sc.hasNext()) {
                String word = sc.next();
                if (map.containsKey(word))
                    map.put(word, map.get(word) + 1);
                else
                    map.put(word, 1);
            }
        }
        System.out.println("yes");
    } catch (IOException e) {
        e.printStackTrace();
    }
    map.entrySet().stream()
              .sorted(Collections.reverseOrder(Map.Entry.comparingByValue()))
              .forEachOrdered(System.out::println);

  }

}

thanks but it does not complile in java7 so i compiled it online and got result like this...... — Gaurav Rajput, Apr 18 '15 at 10:37
str1=5 str2=4 str3=2 ......so if i want only string to print not their corresponding values how will it be — Gaurav Rajput, Apr 18 '15 at 10:47
what do mean by "i want only string to print not their corresponding values" ? what is in your text file you are reading here ? — Alok Mishra, May 08 '15 at 05:39

score 1 · Answer 2 · answered Apr 20 '15 at 10:01

Here is my code using tree map and comparator and gives correct output

import java.io.*;
import java.util.*;

public class DemoComprator {

public static void main(String[] args) {
    Map<String, Integer> map = new LinkedHashMap<>();

        try {
            BufferedReader br = new BufferedReader(new FileReader(new  File(
                    "/home/netiq/Documents/input.txt")));
            String str;
            while ((str = br.readLine()) != null) {
                Scanner sc = new Scanner(str);
                while (sc.hasNext()) {
                    String word = sc.next();
                    if (map.containsKey(word))
                        map.put(word, map.get(word) + 1);
                    else
                        map.put(word, 1);
                }

            }
           // System.out.println("yes");
        } catch (IOException e) {
            e.printStackTrace();
        }
     //   System.out.println(map);
        Comparator<String> comparator=new MyDemoComprator(map);
         Map<String,Integer> treemap=new TreeMap<String, Integer>(comparator);
        treemap.putAll(map);
     //   System.out.println(treemap);
        for(Map.Entry<String, Integer> entry:treemap.entrySet())
        {
            System.out.print(entry.getKey());
            //System.out.println(" :  "+entry.getValue());
            System.out.println();
        }

}

}

class MyDemoComprator implements Comparator<String>
    {
    Map<String,Integer> map;

   public MyDemoComprator(Map<String, Integer> map) {
      super();
       this.map = map;
    }

@Override
public int compare(String o1, String o2) {
    if(map.get(o1)>=map.get(o2))
        return -1;
    else
        return 1;
    //return 0;
}

}

Display words in decreasing order of their occurance

2 Answers2

Here is my code using tree map and comparator and gives correct output