Analysis of my code

Question about the task

Inverted words

Java Multithreading, Level 2, Lesson 9

Resolved

Could someone please explain to me what is wrong with my code????

In the main method, read the name of a file that contains words separated by spaces from the console.
In the text of the file, find all pairs of words that are mirror images of each other. Add them to result.
Use StringBuilder.
The file encoding is UTF-8.

Example of file contents

rat tar tart a
a tot tot tot

Output:

rat tar
a a
tot tot

Requirements:

The main method must read the filename from the keyboard.
The main method must use StringBuilder.
The Solution class must contain a nested Pair class with equals, hashCode, and toString methods. Don't delete or change these methods.
The Pair class must declare a constructor without parameters, i.e. a default constructor.
The result list must be filled with correct pairs according to the task conditions.

package com.codegym.task.task22.task2207; import java.io.*; import java.nio.charset.StandardCharsets; import java.nio.file.Files; import java.nio.file.Paths; import java.util.*; /* Inverted words */ public class Solution { public static List<Pair> result = new LinkedList<>(); public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); //We create a list containing all the lines of our file List<String> list = readFileInList(reader.readLine()); Map<String,String> map1 = new HashMap<String, String>(); Map<String,String> map2 = new HashMap<String, String>(); StringBuilder sb = new StringBuilder(); for(String s: list){ sb.append(s); } String k = sb.toString(); //We create pairs of words by avoiding duplicates. For this we use maps for(String l : list){ String[] tabl = l.split(" "); for(String m : tabl){ String j = (new StringBuilder(m)).reverse().toString(); if(k.contains(j)){ if(m.equals(j)) map1.put(m,m); else map2.put(m,j); } } } //pairs are created from couples for(Map.Entry<String,String> map : map1.entrySet()){ Pair pair = new Pair(); pair.first = map.getKey(); pair.second= map.getValue(); result.add(pair); } for(Map.Entry<String,String> mapy : map2.entrySet()){ Pair pair1 = new Pair(); pair1.first = mapy.getKey(); pair1.second = mapy.getValue(); result.add(pair1); } //Finally, the result is shown for(Pair pair2 : result){ System.out.println(pair2); } } public static class Pair { String first; String second; @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Pair pair = (Pair) o; if (first != null ? !first.equals(pair.first) : pair.first != null) return false; return second != null ? second.equals(pair.second) : pair.second == null; } public Pair() { } @Override public int hashCode() { int result = first != null ? first.hashCode() : 0; result = 31 * result + (second != null ? second.hashCode() : 0); return result; } @Override public String toString() { return first == null && second == null ? "" : first == null ? second : second == null ? first : first.compareTo(second) < 0 ? first + " " + second : second + " " + first; } } //Reading the whole file in a List: Read all lines from a file. This method ensures // that the file is closed when all bytes have been read or an I/O error, or other runtime exception, // is thrown. Bytes from the file are decoded into characters using the specified charset. //public static List readAllLines(Path path,Charset cs)throws IOException /*\u000D followed by \u000A, CARRIAGE RETURN followed by LINE FEED*/ //u000A, LINE FEE /*\u000D, CARRIAGE RETURN*/ public static List<String> readFileInList(String fileName) { List<String> lines = Collections.emptyList(); try { lines = Files.readAllLines(Paths.get(fileName), StandardCharsets.UTF_8); } catch (IOException e) { // do something e.printStackTrace(); } return lines; } }

Comments (7)

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Nouser

Level 36 , Germany

4 March 2021, 18:06

useful

There should only be one pair of matching words in the result list rat tar tar rat should result in rat tar your code spits out rat tar rat tar

Banak

Level 29 , Saint-Gratien, France

5 March 2021, 11:45

here are the modifications that have been made but it still doesn't work !!! for(String l : liste){ String j = (new StringBuilder(l)).reverse().toString(); if(x.contains(j)){ map1.put(l,j); x = x.replace(j,""); } } //pairs are created from couples for(Map.Entry<String,String> map : map1.entrySet()){ Pair pair = new Pair(); pair.first = map.getKey(); pair.second= map.getValue(); result.add(pair); } //Finally, the result is shown for(Pair pair2 : result){ System.out.println(pair2); }

Nouser

Level 36 , Germany

5 March 2021, 13:41

You should post the entire code of the main method, liste and x aren't defined anywhere

Banak

Level 29 , Saint-Gratien, France

5 March 2021, 13:49

BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); //We create a list containing all the lines of our file List<String> list = readFileInList(reader.readLine()); Map<String,String> map1 = new HashMap<String, String>(); StringBuilder sb = new StringBuilder(); for(String s : list){ sb.append(s); } String[] k = sb.toString().split(" "); String x = sb.toString(); ArrayList<String> liste = new ArrayList<>(Arrays.asList(k)); //We create pairs of words by avoiding duplicates. For this we use maps for (String l : liste) { String j = (new StringBuilder(l)).reverse().toString(); if (x.contains(j)) { map1.put(l, j); x = x.replace(j,""); } } //pairs are created from couples for(Map.Entry<String,String> map : map1.entrySet()){ Pair pair = new Pair(); pair.first = map.getKey(); pair.second= map.getValue(); result.add(pair); } //Finally, the result is shown for(Pair pair2 : result){ System.out.println(pair2); }

Nouser

Level 36 , Germany

5 March 2021, 14:11

useful

First I have to admit that I believe I remembered that task in a wrong way ;) You have to display all possible pairs. So the above said was wrong... shame above me. But still your code is doing exactly this. Where it fails is detecting mirror words spawning lines tot tot didn't get fetched You should do some code cleanup. First you read everything into a list, then a BufferedReader into a stringbuilder, from here you split everything... instead you just could read one line, split it and do your searching like

//as long as file has a next line
while (in.ready()) {
    //Iterate through the words of each line
    for (String search : in.readLine().split("\\s+")) {

The problem of your code as it is now, is that you use stringbuilder to append the lines like line1: "abc def ghi" line2: "xyz" result: "abc def ghixyz"

Guadalupe Gagnon

Level 37 , Tampa, United States

5 March 2021, 18:33

solution

I can explain what I did: First read in all the data and split each word. As Nouser said, the words that end a line are being compounded with the words that begin a line. I find it easier to do this: - create FileInputStream - create a byte[] buffer that is the length of the FIS's bytes - read all the bytes to buffer - create string from that buffer - remove all carraige returns - replace all new lines with " " - then split by " " Its only a few lines of code and works well. Create a new list of Strings Then, for each word above, I reverse it (Stringbuilder has a reverse function), see if it is contained in the list. If it is contained, then I remove it from the list, create a new pair with the word and its reverse, and add it to the result list. If it is not contained then I add the word to the list psuedo code: read all data, split by unique word create an ArrayList<String> temp foreach word in dataSplit { create a Stringbuilder(word) reverse that Stringbuilder check if the reverse word (toString()) is in list true { remove word from temp list create a new pair (word, reversedWord) and add to result } false { add word to list } }

Banak

Level 29 , Saint-Gratien, France

8 March 2021, 21:00

thank you, you are very helpful.