How do we ensure the alteration of labels properly?

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This is quite an interesting task, actually. I'm supposed to create a list that merges lines from two files: the original one and its updated version. The lines should be preceded by suitable labels: SAME, REMOVED OR ADDED. The tricky requirement is that the ADDED and REMOVED labels should not be used consecutively: there always has to be a line with the SAME label between them. I can't imagine how it is possible to fully satisfy this condition, taking into consideration that the number of SAME lines might be just insufficient to ensure the alteration. I tried checking for the previous label used before adding every new line, but that strategy didn't get me anywhere (just the code became cumbersome). For instance, if the previous label is ADDED or REMOVED, and the next label is also ADDED or REMOVED, what should I do with it? Should I postpone adding the next lines to the list before a line with the SAME label is found? But what if there are too many postponed lines? So, here is my code attached. I tried it with with some files of my own, here is the input and output I got. File1 ("original"): I love the sunset. It's a beautiful time. The day is all ahead. The buses are not making any noise. The birds are singing. It's neither hot, nor cold. Cool! File2 ("updated"): I love the sunset. It's a romantic time. Could one imagine a better one? The day is all ahead. The buses start going around the city. The birds are singing. It's neither hot, nor cold. Cool! Precious! Output (the contents of the "lines" list): SAME : I love the sunset. ADDED : It's a romantic time. REMOVED : It's a beautiful time. ADDED : Could one imagine a better one? SAME : The day is all ahead. ADDED : The buses start going around the city. REMOVED : The buses are not making any noise. SAME : The birds are singing. It's neither hot, nor cold. SAME : Cool! ADDED : Precious! What can I do about the sequence of labels?

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 javax.sound.sampled.Line; import java.io.BufferedReader; import java.io.FileReader; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List; import java.io.IOException; /* Tracking changes Compare the lines at the current positions of the pointers: */ public class Solution { public static List<LineItem> lines = new ArrayList<>(); public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String file1 = br.readLine(); String file2 = br.readLine(); br.close(); //String file1 = "C:\\Users\\passe\\Documents\\File1.txt"; //String file2 = "C:\\Users\\passe\\Documents\\File2.txt"; BufferedReader reader1 = new BufferedReader(new FileReader(file1)); List<String> original = new ArrayList<>(); String s = null; while ((s = reader1.readLine()) != null) { original.add(s); } reader1.close(); BufferedReader reader2 = new BufferedReader(new FileReader(file2)); List<String> updated = new ArrayList<>(); String l = null; while ((l = reader2.readLine()) != null) { updated.add(l); } reader2.close(); int orCounter = 0; int updCounter = 0; int i = 0, j = 0; //String lastLabel = ""; while (i < original.size() && j < updated.size()) { String or = original.get(i); String upd = updated.get(j); if (or.equals(upd)) { lines.add(new LineItem(Type.SAME, or)); i++; j++; //lastLabel = "SAME"; } else { if (original.contains(upd)) { lines.add(new LineItem(Type.SAME, upd)); j++; i++; } else { lines.add(new LineItem(Type.ADDED, upd)); j++; } if (updated.contains(or)) { lines.add(new LineItem(Type.SAME, or)); i++; j++; } else { lines.add(new LineItem(Type.REMOVED, or)); i++; } } } while (i < original.size()) { if (updated.contains(original.get(i))) { lines.add(new LineItem(Type.SAME, original.get(i))); //lastLabel = "SAME"; } else { lines.add(new LineItem(Type.REMOVED, original.get(i))); //lastLabel = "REMOVED"; } i++; } while (j < updated.size()) { if (original.contains(updated.get(j))) { lines.add(new LineItem(Type.SAME, updated.get(j))); //lastLabel = "SAME"; } else { lines.add(new LineItem(Type.ADDED, updated.get(j))); //lastLabel = "ADDED"; } j++; } for (LineItem li : lines) { System.out.println(li.type + " : " + li.line); } } 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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Guadalupe Gagnon

Level 37 , Tampa, United States

25 September, 17:30

Your example would be invalid because the task guarantees that the test values will not have two consecutive lines that are ADDED and/or REMOVED, there will always be a line that is SAME in between. You could do it like this instead: File1 ("original"): It's a beautiful time. I love the sunset. The day is all ahead. The buses are not making any noise. The birds are singing. It's neither hot, nor cold. Cool! File2 ("updated"): I love the sunset. It's a romantic time. The day is all ahead. The birds are singing. It's neither hot, nor cold. Could one imagine a better one? Cool! The buses start going around the city. Output (the contents of the "lines" list): REMOVED : It's a beautiful time. SAME : I love the sunset. ADDED : It's a romantic time. SAME : The day is all ahead. REMOVED : The buses are not making any noise. SAME : The birds are singing. It's neither hot, nor cold. ADDED : Could one imagine a better one? SAME : Cool! ADDED : The buses start going around the city. This would be valid input that the validator could use to test and your code does not need to do anything more to check for invalid inputs.

Thomas

Level 41 , Bayreuth, Germany

25 September, 10:33

I'm not really sure what you're asking. Do you want to enhance the code so it has more functionality? The requirement that a ADDED or REMOVED needs to be followed by a SAME is just to make the task easier. The example you posted above violates that requirement and makes it hard(er). So eg. you start with a SAME A A SAME then it can be followed by a ADDED or REMOVED B C C here we have a REMOVED that's followed again by a SAME So it is clear what to do; you compare lines. If the current line from file a is the same as the current line from file b you have a next. If not: If the current line from file a matches the next line of file b you have an ADDED if not: If the current line from file b matches the next line of file a you have a REMOVED then you just need to get out of the loop if either side has no more entries and as a last thing you need to check if the other side has an entry left that (then you have another ADDED or REMOVED). The way you have it now is trying to do way more than asked.

Evgeniia Shabaeva

Level 32 , Budapest, Hungary

1 October, 10:50

Thank you very much for the advice. My basic worry is what happens if the merged file, for instance, has only three SAME lines, while, idk, ten lines are REMOVED and nine are ADDED. How is it possible to have SAME every second time then?

Thomas

Level 41 , Bayreuth, Germany

1 October, 12:35

It is a requirement to the source. Means Codegym just uses such files to test your code that fullfill the requirement. Ever REMOVED or ADDED needs to be followed by a SAME (except the last). But a SAME can be followed by a SAME. So basically it can not happen that the merged file has lots more ADDED/REMOVE than SAME (max one more).

Evgeniia Shabaeva

Level 32 , Budapest, Hungary

15 October, 08:26

Well, I see now, thank you. If the source material meets the requirements, that must be possible...