Why is this wrong?

Question about the task

Tracking changes

Java Core, Level 9, Lesson 11

Resolved

The feedback I get from. my mentor doesn't make sense...

Read 2 file names from the console: file1 and file2.
Both files contain text, but file2 is an updated version of file1. Some of the lines are still the same.
You need to create a merged version of the lines by writing them to the lines list.
The ADDED and REMOVED labels can't be used consecutively—they must always separated by the SAME label.
The example includes empty lines for clarity.
Neither the original file nor the updated file have empty lines!

Example 1:
original updated merged file1: file2: Result: (lines) line1 line1 SAME line1 line2 REMOVED line2 line3 line3 SAME line3 line4 REMOVED line4 line5 line5 SAME line5 line0 ADDED line0 line1 line1 SAME line1 line2 REMOVED line2 line3 line3 SAME line3 line4 ADDED line4 line5 line5 SAME line5 line0 REMOVED line0

Example 2:
original updated merged file1: file2: Result: (lines) line1 line1 SAME line1 line0 ADDED line0

In the example, empty lines mean that the line is not in the specified file.

Requirements:

The Solution class must contain a LineItem class.
The Solution class must have an enum called Type.
The Solution class must have a public static List<LineItem> field called lines that is initialized immediately.
In the main(String[] args) method, the program must read file names from the console (use BufferedReader).
In the main(String[] args) method, the BufferedReader used for reading input from the console must be closed after use.
The program must read the contents of the first and second file (use FileReader).
The file input streams (FileReader) must be closed.
The lines list should contain the merged version of the lines from the files. Each line should start with the label ADDED, REMOVED, or SAME, depending on the action taken.

package com.codegym.task.task19.task1916; import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List; /* Tracking changes */ public class Solution { //3. The Solution class must have a public static List<LineItem> field called lines that is initialized immediately. public static List<LineItem> lines = new ArrayList<>(); public static void main(String[] args) throws IOException { //4. In the main(String[] args) method, the program must read file names from the console (use BufferedReader). BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String file1 = reader.readLine(); String file2 = reader.readLine(); //5. In the main(String[] args) method, the BufferedReader used for reading input from the console must be closed after use. reader.close(); //6. The program must read the contents of the first and second file (use FileReader). //Wrap it in a buffered reader as I want to use readLine() BufferedReader reader1 = new BufferedReader(new FileReader(file1)); BufferedReader reader2 = new BufferedReader(new FileReader(file2)); //8. The lines list should contain the merged version of the lines from the files. // Each line should start with the label ADDED, REMOVED, or SAME, depending on the action taken. String line1, line2; while(reader1.ready() && reader2.ready()){ line1 = reader1.readLine(); line2 = reader2.readLine(); if(line1.equals(line2)) lines.add(new LineItem(Type.SAME, line1)); else if (line2.isEmpty()) lines.add(new LineItem(Type.REMOVED, line1)); else lines.add(new LineItem(Type.ADDED, line2)); } //7. The file input streams (FileReader) must be closed. reader1.close(); reader2.close(); } //2. The Solution class must have an enum called Type. public static enum Type { ADDED, // New line added REMOVED, // Line deleted SAME // No change } //1. The Solution class must contain a LineItem class. public static class LineItem { public Type type; public String line; public LineItem(Type type, String line) { this.type = type; this.line = line; } } }

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Nouser

Level 36 , Germany

10 January 2021, 16:06

The task conditions here are very confusing as there are no empty lines in the files that you could use as markers to compare with. it's more like File1: text-line1 text-line2 text-line3 text-line5 File2: text-line1 text-line3 text-line4 text-line5 result: SAME --- text-line1 REMOVED --- text-line2 SAME --- text-line3 ADDED --- text-line4 SAME --- text-line5 text-line2 doesn't exist in file2, hence removed text-line4 exist just in file2, therfore you need to write added And for a final check if all works you add text-line6 to one of the files (alternate)

Liliane Top Backend Developer at Procura

10 January 2021, 16:41

rewrote the code but I just realised that I have't taken into account that the files can have different lengths....

Liliane Top Backend Developer at Procura

10 January 2021, 16:43

Now I have to think of a solution about the different lenghts of the files

for (int i = 0; i < lines1.size(); ) {
           for (int j = 0; j < lines2.size(); ) {
               if (lines1.get(i).equals(lines2.get(j))) {
                   lines.add(new LineItem(Type.SAME, lines1.get(i)));
                   i++;
                   j++;
                   //if they are not the same a line is either added to file2 or removed
                   //which will always be followed with 2 lines the SAME;
               } else {
                   if (lines1.get(i + 1).equals(lines2.get(j))) {
                       lines.add(new LineItem(Type.REMOVED, lines1.get(i)));
                       i++;
                   } else {
                       lines.add(new LineItem(Type.ADDED, lines2.get(j)));
                       j++;
                   }
               }
           }

       }

Nouser

Level 36 , Germany

10 January 2021, 16:49

You should consider, that every second result needs to be a SAME: The ADDED and REMOVED labels can't be used consecutively—they must always separated by the SAME label. So if you find line_x ----- line_y then you know.. the previous labale was SAME and the next will be SAME and here you find a pair if you compare line_x with the line following line_y or you when you compare the following line of line_x with line_y It is a big help to read this line and the following line into a variable... and that of course for both files.

Liliane Top Backend Developer at Procura

10 January 2021, 19:54

for (int i = 0, j = 0; i < lines1.size() || j < lines2.size();) {
            int pos = checkSize(i, j, lines1.size(), lines2.size());
            switch (pos) {
                case 1:
                    addLineAdded(lines2.get(j));
                    j++;
                    break;
                case 2:
                    addLineRemoved(lines1.get(i));
                    i++;
                    break;
                case 3:
                    //step2: check if they are the same
                    int compare = checkSameness(lines1.get(i), lines2.get(j), lines1.get(i + 1));
                    switch (compare) {
                        case 1:
                            addLineSame(lines1.get(i));
                            i++;
                            j++;
                            break;
                        case 2:
                            addLineRemoved(lines1.get(i));
                            i++;
                            break;
                        case 3:
                            addLineAdded(lines2.get(j));
                            j++;
                            break;
                    }
                    break;
            }
        }
        for (LineItem x : lines) {
            System.out.println(x.type.toString() + " " + x.line);
        }
    }
   public static int checkSize(int i, int j, int sizeA, int sizeB) {
        return (i == sizeA && j < sizeB) ? 1 : (i < sizeA && j == sizeB) ? 2 : 3;
    }
    private static int checkSameness(String s1, String s2, String s3) {
        return (s1.equals(s2)) ? 1 : s3.equals(s2) ? 2 : 3;
    }
    public static void addLineAdded(String s) {
        lines.add(new LineItem(Type.ADDED, s));
    }
    public static void addLineRemoved(String s) {
        lines.add(new LineItem(Type.REMOVED, s));
    }
    public static void addLineSame(String s) {
        lines.add(new LineItem(Type.SAME, s));

Liliane Top Backend Developer at Procura

10 January 2021, 19:55

I solved it then refactored it but now I fail the test and I do not know why. Can you help me please? It says : Be sure that the lines list has the SAME label with the required lines in the correct places. My output seems to be fine....

Liliane Top Backend Developer at Procura

10 January 2021, 20:49

solution

I had to change case 3: but now my code is becoming spaghetti again. Time to move on:

case 3:
                   //step2: check if they are the same
                   if (checkSameness(lines1.get(i), lines2.get(j))) {
                       addLineSame(lines1.get(i));
                       i++;
                       j++;
                   } else if (i != (lines1.size() - 1)) {
                       if (checkSameness(lines1.get(i + 1), lines2.get(j))) {
                           addLineRemoved(lines1.get(i));
                           i++;
                       } else {
                           addLineAdded(lines2.get(j));
                           j++;
                       }
                   } else if (j != (lines2.size() - 1)) {
                       addLineAdded(lines2.get(j));
                       j++;
                   }
                   break;

Nouser

Level 36 , Germany

10 January 2021, 21:15

text-line1 text-line2 text-line3 text-line1 text-line2 add text-line3 this fails cause of your loop (int i = 0, j = 0; i < lines1.size() || j < lines2.size();) together with checking sameness checkSameness(lines1.get(i), lines2.get(j), lines1.get(i + 1)) when lines1 is already at its limit you still can excess its limits with the +1 in the check. Means you need a lot of more checking here, pita And I love your code... ;) Edit: Oh, OK, you already have found your solution, congrats