Why do I fail the test?

Question about the task

Resolved

Is si because I use Scanner and I should use a bufferedReader? if so why? And what is the difference between: allLines.removeAll(linesForRemoval); && linesForRemoval.clear(); ??

Make the joinData method transactional, i.e. if it fails, then the data must not be changed.
1. Read 2 file names from the console.
2. Read from the files line by line. Read from the first file into allLines, from the second file — into linesForRemoval.
In the joinData method:
3. If the allLines list contains all the lines from linesForRemoval, then remove from the allLines list all the lines that are in linesForRemoval.
4. If the condition in Item 3 is not satisfied, then:
4.1. clear the data in allLines
4.2. throw a CorruptedDataException
The joinData method should be called in main. Handle all exceptions in the main method.
Don't forget to close the streams.

Requirements:

The Solution class must contain a public static List<String> field called allLines.
The Solution class must contain a public static List<String> field called linesForRemoval.
The Solution class must have a public void joinData() method that can throw a CorruptedDataException.
The program should read the names of two files from the console.
The program must read line by line from the first file into the allLines list.
The program must read line by line from the second file into the linesForRemoval list.
The joinData method must remove from the allLines list all lines in the linesForRemoval list if allLines contains all the lines in the linesForRemoval list.
The joinData method must clear the allLines list and throw a CorruptedDataException, if allLines does not contain all the lines in the linesForRemoval list.
The joinData method should be called in main.

package com.codegym.task.task17.task1721; import java.io.*; import java.util.ArrayList; import java.util.List; import java.util.Scanner; /* Transactionality */ public class Solution { public static List<String> allLines = new ArrayList<>(); public static List<String> linesForRemoval = new ArrayList<>(); public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String filename1 = ""; String filename2 = ""; try { filename1 = reader.readLine(); filename2 = reader.readLine(); } catch (IOException e) { e.printStackTrace(); } Scanner scanner = new Scanner(new File(filename1)); Scanner scanner2 = new Scanner(new FileReader(filename2)); String line; while (!scanner.nextLine().isEmpty()) { line = scanner.nextLine(); allLines.add(line); } while (!scanner2.nextLine().isEmpty()) { line = scanner2.nextLine(); linesForRemoval.add(line); } reader.close(); scanner.close(); scanner2.close(); Solution solution = new Solution(); solution.joinData(); } public void joinData() throws CorruptedDataException { if (allLines.containsAll(linesForRemoval)) { allLines.removeAll(linesForRemoval);//what is the difference with linesForRemoval.clear() } else { allLines.clear(); throw new CorruptedDataException(); } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

29 December 2020, 18:53

Each call to the scanner.nextLine() method reads the next line:

while (!scanner.nextLine().isEmpty()) { // one read
   line = scanner.nextLine(); // two read
   allLines.add(line);
}

This bit of code reads two lines, one on the first line and one on the second line, at a time but only adds one of those lines to the allLines List.

Liliane Top Backend Developer at Procura

29 December 2020, 18:57

Scanner scanner = new Scanner(new FileReader(filename1));
       String line;
       while (scanner.hasNextLine()) {
           line = scanner.nextLine();
           allLines.add(line);
       }

       try {
           filename2 = reader.readLine();
       } catch (IOException e) {
           e.printStackTrace();
       }

       Scanner scanner2 = new Scanner(new FileReader(filename2));
       while (scanner.hasNextLine()) {
           line = scanner2.nextLine();
           linesForRemoval.add(line);
       }

       reader.close();
       scanner.close();
       scanner2.close();

if I run this code it accept the the first scanner but not the second

Nouser

Level 36 , Germany

29 December 2020, 19:09

solution

in line 15 you meant to write scanner2

Guadalupe Gagnon

Level 37 , Tampa, United States

29 December 2020, 19:10

useful

The problem is line 15 on the code above (scanner2, not scanner). Something I tell most everyone is that you should try to only have one stream open at any given time. The reason is that streams are very resource intensive. In this code I would recommend opening the first stream to read the file names then closing that stream; then open each file reading stream one a time and closing it upon finishing:

BufRd  r= new BR(ISR(S.I)); // open
//do work ↓
file1 = r.rL();
file2 = r.rL();
r.close; //close

scan1 = new S(file1); // open
//do work ↓
while(/**/) {
   //...
}
scan1.close(); // close

scan2 = new S(file2); // open
//do work ↓
while(/**/) {
   //...
}
scan2.close(); // close

This would make your code more efficient.

Liliane Top Backend Developer at Procura

29 December 2020, 19:16

I 'm so annoyed with myself. 👿I spend so much time figuring out why it wasn't working and it was just a typo!! Thanks for pointing it out to me otherwise it would have been a long night.🤪