Pardon the poetry. But the validator does not let me pass still.

Question about the task

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My strategy was to create copy arraylists and then insert the word "empty" to the list where an item got added or removed. The examples worked perfectly but it didn't pass the validator.

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.util.ArrayList; import java.util.List; import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.FileNotFoundException; import java.io.IOException; import java.io.FileReader; /* Tracking changes */ public class Solution { public static List<LineItem> lines = new ArrayList<>(); public static void main(String[] args) { try(BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); BufferedReader fileReaderOne = new BufferedReader(new FileReader(reader.readLine())); BufferedReader fileReaderTwo = new BufferedReader(new FileReader(reader.readLine()))) { ArrayList<String> fileOneLines = new ArrayList<>(); ArrayList<String> fileTwoLines = new ArrayList<>(); while(fileReaderOne.ready()) { String line = fileReaderOne.readLine(); fileOneLines.add(line); } while(fileReaderTwo.ready()) { String line = fileReaderTwo.readLine(); fileTwoLines.add(line); } ArrayList<String> fileOneCopy = new ArrayList<>(); ArrayList<String> fileTwoCopy = new ArrayList<>(); fileOneCopy.addAll(fileOneLines); fileTwoCopy.addAll(fileTwoLines); int x = 0; int y = 0; for (int i = 0; i < fileOneLines.size(); i++) { if (fileOneCopy.get(x).equals(fileTwoCopy.get(y))) { x++; y++; } else { x++; if (fileOneCopy.get(x).equals(fileTwoCopy.get(y))) { fileTwoCopy.add(x - 1, "empty"); y++; } else { x--; } y++; if (fileOneCopy.get(x).equals(fileTwoCopy.get(y))) { fileOneCopy.add(y - 1, "empty"); x++; } else { y--; } } } while(fileOneCopy.size() != fileTwoCopy.size()) { if (fileOneCopy.size() > fileTwoCopy.size()) { fileTwoCopy.add("empty"); } else if (fileOneCopy.size() < fileTwoCopy.size()){ fileOneCopy.add("empty"); } } for (int i = 0; i < fileOneCopy.size(); i++) { if (fileOneCopy.get(i).equals(fileTwoCopy.get(i))) { lines.add(new LineItem(Type.SAME, fileOneCopy.get(i))); } else if (fileOneCopy.get(i).equals("empty")) { lines.add(new LineItem(Type.ADDED, fileTwoCopy.get(i))); } else if (fileTwoCopy.get(i).equals("empty")) { lines.add(new LineItem(Type.REMOVED, fileOneCopy.get(i))); } } for (LineItem lineItem : lines) { switch (lineItem.type) { case ADDED: System.out.println("ADDED " + lineItem.line); break; case REMOVED: System.out.println("REMOVED " + lineItem.line); break; case SAME: System.out.println("SAME " + lineItem.line); break; } } } catch (FileNotFoundException e) { System.out.println("File not found"); } catch (IOException e) { System.out.println("Something went wrong"); } } public static enum Type { ADDED, // New line added REMOVED, // Line deleted SAME // No change } 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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Thomas

Level 41 , Bayreuth, Germany

22 May 2023, 06:40

When accessing arrays (or array lists) you need to be extra careful to stay inside the bounds of that array. Let's look at your loop over fileOneLines. Here you not only access fileOneLines but also fileTwoCopy with the same index. Not only that. In certain cases you even access loopCounter + 1 of the second list. Now you just need to think about a test case where list 1 has elements at loop index i and list 2 not and you get eg.: line1 line1 line2 Just that primitive example will throw the IndexOutOfBoundsException. You need to fix this bug to validate the task. And that is a really difficult task. So do not be discouraged.

Untitled by Anon

Level 49 , Germany

22 May 2023, 09:57

Thank you for your advice. Will continue to find a new solution for it.

alberto weber

Level 28 , Poland, Poland

21 May 2023, 17:00

I recomend using anwser given by codegym to compare Your code. At first sight I can tell that it should work but maybe validator doesn't like adding labels this way. Additionally it's a good practice to not define List in declaration what I mean is instead of

ArrayList<String> fileOneLines = new ArrayList<>();
//it's better to write
List<String> fileOneLines = new ArrayList<>();

It's beacuse if in the future you will want to change array list to other list you will have a lot of work to do and types won't match. Hope u will find Your soulution soon !

Untitled by Anon

Level 49 , Germany

22 May 2023, 09:58

Thanks. I changed the declaration.