CodeGym/Help with Java Tasks/Infinite loop somewhere?

Level 30

London

29.01.2020
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Infinite loop somewhere?

Question about the task

Tracking changes

Java Core, Level 9, Lesson 11

Resolved

My code keeps failing because : The program ran too long and was closed! No idea why though

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.*; import java.util.ArrayList; import java.util.List; /* Tracking changes */ public class Solution { public static List<LineItem> lines = new ArrayList<>(); public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String file1 = reader.readLine(); String file2 = reader.readLine(); reader.close(); ArrayList<String> file1Contents = fileReader(file1); ArrayList<String> file2Contents = fileReader(file2); sameLines(file1Contents, file2Contents); removedLines(file1Contents, file2Contents); addedLines(file1Contents, file2Contents); notConsecutive(lines); } 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; } } //read file lines and add to arraylist public static ArrayList<String> fileReader(String fileName) throws IOException { ArrayList<String> list = new ArrayList<>(); try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) { String s; while ((s = reader.readLine()) != null) list.add(s); } return list; } //check if lines are the same public static void sameLines(ArrayList<String> file1Contents, ArrayList<String> file2Contents){ for (String s : file1Contents){ if (file2Contents.contains(s)) lines.add(new LineItem(Type.ADDED, s)); } } //check if lines are removed public static void removedLines(ArrayList<String> file1Contents, ArrayList<String> file2Contents){ for (String s : file1Contents){ if (!file2Contents.contains(s)) lines.add(new LineItem(Type.REMOVED, s)); } } //check if lines are added public static void addedLines(ArrayList<String> file1Contents, ArrayList<String> file2Contents){ for (String s : file2Contents){ if (!file1Contents.contains(s)) lines.add(new LineItem(Type.ADDED, s)); } } // make sure removed & added are not consecutive public static void notConsecutive(List<LineItem> lines){ for (int i = 0; i<lines.size()-1; i++){ if (lines.get(i).type==lines.get(i+1).type && lines.get(i).type!=Type.SAME){ insertSame(lines, i+1); } } } static int count = 0; // insert same type between consecutive types public static void insertSame(List<LineItem> lines, int index){ while (lines.get(count).type!=Type.SAME){ if (count == lines.size()-1) count = 0; else count++; } lines.add(index, lines.get(count)); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

29 January 2020, 15:06

useful

The insertSame method has a while loop that run as long as the item does not have the type SAME. Looking through the code I see that at lines 64, 72, and 80 has ADDED, REMOVED, ADDED... but no SAME. This is causing your infinite loop. Now with that being said I don't think this will pass verification the way that it is. The 'lines' array should hold the merged result of both files in correct order. The way the program should work is that it should compare the lines starting from the top and moving sequentially. If they are the same then add it to the combined List as SAME, if they are different the code should figure out if it an ADDED line or REMOVED line, then add it to the List tagged correctly. A quick example: File1 File2 “test line” “test line” “not same” “this is different” “something ” “not same” “back to same” “back to same” Merged “test line” – SAME ““this is different” - ADDED “not same” - SAME “something ” – REMOVED “back to same” - SAME

Anthony Chalk

Level 30 , London, United Kingdom

29 January 2020, 15:11

Aha, silly mistake. Right, I'm so confused by the task requirements, especially the fact that: The ADDED and REMOVED labels can't be used consecutively—they must always separated by the SAME label. I mean, hypothetically if I had the following files File1 File2 “aaaa” “eeee” “bbbb” “ffff” “cccc ” “gggg” “dddd” “hhhh” how would that work?

Guadalupe Gagnon

Level 37 , Tampa, United States

29 January 2020, 15:18

"The ADDED and REMOVED labels can't be used consecutively—they must always separated by the SAME label." This is the best part about this task. When I did this task back in 2018 they didn't have that stated and my code was a mess. I had no idea how to determine what the tags were. This requirement made figuring out how to complete it So much easier, an easier way to keep things sequential.

Anthony Chalk

Level 30 , London, United Kingdom

29 January 2020, 15:20

So I should just write my code under the assumption that there won't be too many lines in a row that are ADDED or REMOVED?

Guadalupe Gagnon

Level 37 , Tampa, United States

29 January 2020, 15:22

solution

If you use the tag ADDED or REMOVED, the very next tag must be SAME.

Guadalupe Gagnon

Level 37 , Tampa, United States

29 January 2020, 15:23

So File1 File2 “aaaa” “eeee” “bbbb” “ffff” “cccc ” “gggg” “dddd” “hhhh” This would not be part of the verification because there are no lines that are the same.

Anthony Chalk

Level 30 , London, United Kingdom

29 January 2020, 15:29

Ah okay, that's where I was getting confused (I assume that must mean that the files are the same length (within 1 line) also) I'll try this again Thank you

Anthony Chalk

Level 30 , London, United Kingdom

29 January 2020, 22:49

Solved it; thank you

Gabriel Kieruzel

Level 26 , Katowice, Poland

17 March 2020, 19:45

Hello, Went to the same conclusion, even used your code snippet ( but with understanding how it works ). Anyway still have this validation error: "Be sure that the lines list has the ADDED label with the required lines in the correct places" No idea what next as results seem to be as expected, but no pass. Regards.

Anthony Chalk

Level 30 , London, United Kingdom

17 March 2020, 21:25

I pretty much completely redid my code to pass. In the posted one I was working under the (incorrect) assumption that there could potentially be added/removed lines consecutively and you would have to manually add SAME lines in between. What does your code look like

Gabriel Kieruzel

Level 26 , Katowice, Poland

18 March 2020, 06:06

Thank you for your answer. I'm just trying to follow what was explained in this forum, I was convinced it works as expected but now I'm stuck as the test engine is saying something is wrong with my ADDED lines, here is the code:

String file1;
        String file2;
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        file1 = bufferedReader.readLine();
        file2 = bufferedReader.readLine();
        bufferedReader.close();
        String[] files = {file1, file2};
        List<String> linesFromOriginal = new ArrayList<>();
        List<String> linesFromUpdated = new ArrayList<>();
        for (int i = 0; i < files.length; i++) {
            BufferedReader br = new BufferedReader(new FileReader(files[i]));
            while (br.ready()) {
                if (i == 0) {
                    linesFromOriginal.add(br.readLine());
                }
                else
                    {
                    linesFromUpdated.add(br.readLine());
                }
            }
            br.close();
        }
while ((updatedIndex < linesFromUpdated.size()) && (originalIndex < linesFromOriginal.size())) {
            String originalLine = linesFromOriginal.get(originalIndex);
            String updatedLine = linesFromUpdated.get(updatedIndex);
            if (updatedLine.equals(originalLine)) {
                lines.add(new LineItem(Type.SAME,   updatedLine));
                originalIndex++;
                updatedIndex++;
            }
            else if ((originalIndex + 1 < linesFromOriginal.size()) &&    (updatedLine.equals(linesFromOriginal.get(originalIndex +1)))) {
                lines.add(new LineItem(Type.REMOVED,  originalLine));
                originalIndex++;
            }
            else {
                lines.add(new LineItem(Type.ADDED,updatedLine));
                updatedIndex++;
            }