Why does it not work?

Question about the task

Symbol frequency

Java Core, Level 8, Lesson 11

Under discussion

While testing on IntelliJ it works fine, output is also fine. Any help?

The program is started with one argument: the name of a file that contains text.
Calculate how often each symbol is encountered.
Sort the results by increasing ASCII code (read about it online).

Example:
','=44, 's'=115, 't'=116.

Display the sorted results:
[symbol1] frequency1
[symbol2] frequency2
Close the streams.

Example output:
, 19 - 7 f 361

Requirements:

You don't need to read anything from the console.
Create a stream to read from the file passed as the first argument of the main method.
You need to calculate the frequency of each symbol in the file and display the results.
The displayed results should be sorted by ascending ASCII code.
The stream used to read the file must be closed.

package com.codegym.task.task18.task1821; /* Symbol frequency */ import java.io.*; import java.util.Map; import java.util.TreeMap; public class Solution { public static void main(String[] args) throws IOException, FileNotFoundException { BufferedReader reader = new BufferedReader(new FileReader(args[0])); TreeMap<Character,Integer> map = new TreeMap<>(); int counter = 0; while (reader.ready()) { String data = reader.readLine(); char[] arr = data.toCharArray(); for (int i = 0; i<arr.length; i++) { for (int j = 0; j<arr.length; j++) { if (arr[i] == arr[j]) { counter++; } } map.put(arr[i],counter); counter = 0; } } reader.close(); for (Map.Entry<Character,Integer> copy : map.entrySet()) { System.out.println(copy.getKey()+ " "+copy.getValue()); } } }

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hidden #10611437

Level 24

13 May 2020, 12:50

I'm struggling to understand your reasoning for the nested the loops. A single loop would suffice in this case. Loop through the char array and on each character check whether the map already contains the character, if not add the character and the value of 1, if it does then just increment the value. Hope that makes sense :)

Rafał Pawłowski

Level 22 , Southampton, United Kingdom

13 May 2020, 12:57

package com.codegym.task.task18.task1821;

/*
Symbol frequency

*/

import java.io.*;
import java.util.Map;
import java.util.TreeMap;

public class Solution {
    public static void main(String[] args) throws IOException, FileNotFoundException {
        BufferedReader reader = new BufferedReader(new FileReader(args[0]));
        TreeMap<Character,Integer> map = new TreeMap<>();
        int counter = 0;

        while (reader.ready()) {
            String data = reader.readLine();
            char[] arr = data.toCharArray();

            for (int i = 0; i<arr.length; i++) {
                if (map.containsKey(arr[i])) {
                    counter++;
                }
                else {
                    map.put(arr[i], counter=1);
                }
            }
        }
        reader.close();

        for (Map.Entry<Character,Integer> copy : map.entrySet()) {
            System.out.println(copy.getKey()+ " "+copy.getValue());
        }
    }
}

Still the same, did not helped out. I have found double loop easier. First loop checks character, seconds checks if next character is the same. If it is counter goes up by 1

hidden #10611437

Level 24

13 May 2020, 13:02

Try this and remove your counter variable.

for (int i = 0; i<arr.length; i++) {
                if (map.containsKey(arr[i])) {
                    map.put(arr[i], map.get(arr[i])++);
                }
                else {
                    map.put(arr[i], 1);
                }
            }

hidden #10611437

Level 24

13 May 2020, 13:03

I think the problem with your solution is that every time you read a new line you end up overwriting the values you've already put inside of the map

Rafał Pawłowski

Level 22 , Southampton, United Kingdom

13 May 2020, 13:09

Still not working. Even if doing map.get(arr[i])++); will make character go up by one. My solution works if you will open it up with any text file which you can check on your own. Unfortunately you cannot test it with args[0] so I usually make my own file with my own path and use it to test my solutions. I do not know why it does not work on the server tho

Thomas

Level 41 , Bayreuth, Germany

13 May 2020, 13:46

A BufferedReader isn't the best solution here. Better would be a FileInputStream as it gives you 'really' all data saved in the file. BufferedReader gives you lines and afaik it removes the endline symbol. And my guess is, that's the problem here, If you use FIS, then the rest is a one liner (with a TreeMap as you have and map.merge)

while (fis.available() > 0) map.merge((char) fis.read(), 1, Integer::sum);