Is there a smarter way to do this? Anyway, h - java help on CodeGym

Let me know if there is a better way to do this. I was thinking of using some kind of a sorted map instead of iterating through the entrySet and storing the highest values, but I did not find relevant information regarding this.

package com.codegym.task.task18.task1823;

import java.io.*;
import java.security.KeyStore;
import java.util.*;

/*
Threads and bytes

*/

public class Solution {
    public static Map<String, Integer> resultMap = new HashMap<String, Integer>();

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        //read filenames from the console until the word "exit" is entered
        //pass the filename to the readthread thread
        //the thread should find the byte (so the element, not how many times it occurs)
        //that occurs most frequently in the file and add it to
        //the resultMap where the String parameter is the fileName and the Integer parameter is
        //the relevant byte.

        while (true){
            String fileName = br.readLine();
            if (fileName.equals("exit")) {
                br.close();
                break;
            }
            ReadThread readThread = new ReadThread(fileName);
            readThread.start();
        }
    }

    public static class ReadThread extends Thread {
        String fileName;
        public ReadThread(String fileName) throws FileNotFoundException {
            // Implement constructor body
            this.fileName = fileName;

        }
        public void run(){
        // Implement file reading here
            //I have created a map in which I will add all of the elements from the file
            //and the number of times they are found
            HashMap<Integer, Integer> sortedMap = new HashMap<>();
            try {
                FileInputStream fileInputStream = new FileInputStream(fileName);
                //here I am reading the bytes from the file
                while (fileInputStream.available()>0){
                    int byteRead = fileInputStream.read();
                    //the condition below checks if the file is present and increments value
                    //or adds the key to the map and value 1 because it is the 1st time it shows up
                    if (sortedMap.containsKey(byteRead)){
                        sortedMap.replace(byteRead, sortedMap.get(byteRead) + 1);
                    } else sortedMap.put(byteRead, 1);
                }
                //here I declare a value and key which will store value and key when I iterate
                //through the map
                int value = Integer.MIN_VALUE;
                int key = 0;
                //declaring the entry set -a clone- of the sortedMap
                Set<Map.Entry<Integer,Integer>> entries = sortedMap.entrySet();
                //iterating through the clone
                for(Map.Entry<Integer,Integer> entry:entries) {
                    if(entry.getValue() >= value) {
                        value = entry.getValue();
                        key = entry.getKey();
                    }
                }
                resultMap.put(fileName, key);
                fileInputStream.close();

            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

public void run() { try (BufferedInputStream in = new BufferedInputStream(new FileInputStream(fileName))) { while (in.available() > 0) { //used a lambda for the BiFunction as it is better readable for me than a method reference (Integer::sum here) map.merge((char) in.read(), 1, (a, b) -> a + b); } } catch (IOException ioe) { /* ignore */ } //find highest value for (Map.Entry<Character, Integer> pair : map.entrySet()) { if (pair.getValue() > mostFrequentByte) { mostFrequentByte = pair.getKey(); } } }

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Nouser

Level 36 , Germany

2 February 2021, 15:48

I've solved that using map merge (compute should do as well but you need more code in the BiFunction and take care of the null value). Disadvantage is that it is hard to understand. I have to look up the implementation of the merge method to get the hang of it. On the other side you have very short code. And once you know about that method you not only can merge one value into a map but entire collections.

Andrei

Level 41

2 February 2021, 16:18

I got to say, the map merge function, currently is above my bag of knowledge 😁

Guadalupe Gagnon

Level 37 , Tampa, United States

28 January 2021, 15:50

solution

This isn't a bad solve. The thing that I would change is the reading of the file. If you are going to use a FileIntputStream then reading 1 byte at a time is exponentially slower than other methods. If you had a file that was 1 mb in length, reading 1 byte at a time would take close to 10 seconds. You can either use a BufferedReader, BufferedInputStream, or the raw FileIntputStream with a buffer and read the file in one shot. I timed each method on my computer with a 1 mb file: FileInputStream reading 1 at a time: 9845 ms <<< slow reading all at once: 1 ms BufferedReader: 1 at a time: 74 ms line by line: 33 ms BufferedInputStream 1 at a time: 3003 ms <<< fairly slow all at once: 1 ms

28 January 2021, 16:11

Yes, good idea, thanks!

Is there a smarter way to do this? Anyway, here is a solution: USE AS A GUIDE, NOT COPY-PASTE! It's best if you try and reproduce the exercise from your mind, this way you will learn better