Hashmap implementation to count the occurrences of each character

Question

The below code is to count the occurrence of each character and it should print the count. But with the code, I have tried I get only a 1 and I don’t know the changes I should make.

import java.io.BufferedReader;

import java.io.DataInputStream;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.util.HashMap;

import java.util.Map;

class Count_CharMap {

public static void main(String[] args) {

    try

    {

        FileInputStream file = new FileInputStream("D:\\trial.txt");

        DataInputStream dis = new DataInputStream(file);

        BufferedReader br = new BufferedReader(new InputStreamReader(dis));

        String Contents="";

        String str="";

        while ((Contents = br.readLine()) != null) {

            str+=Contents;

        }

        char[]char_array =str.toCharArray();

        int count = 0;

        char ch = char_array[count];

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

        for(int i=0;i<str.length();i++)

        {

            if(charCounter.containsKey(char_array[i]))

            {

                charCounter.put(ch, charCounter.get(ch)+1);

            } 

            else

            {

                charCounter.put(ch, 1);

            }

       }

       for(Character key:charCounter.keySet())

       {

           System.out.println(key+""+charCounter.get(key));

       }

    } 

    catch(IOException e1){

        System.out.println(e1);

    }

    }

}

The actual output should be like if I have abcdabc in my text file  it should print a 2 b 2 c 2 d 1

Answer 1

You are leaving char ch set as the same character through each execution of the loop.

It should be:

ch = char_array[i]; 

if(charCounter.containsKey(ch)){

     charCounter.put(ch, charCounter.get(ch)+1);

}

else

{

    charCounter.put(ch, 1);

}

Inside the for loop.

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