CodeGym/Help with Java Tasks/Task1630 Output is correct

Level 20

SPb

07.05.2019
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Task1630 Output is correct

Question about the task

Sequential file output

Java Core, Level 6, Lesson 13

Resolved

Help, please. What's wrong in my code? Output is correct.

1. Figure out what the program does.
2. In a static block, read 2 filenames: firstFileName and secondFileName.
3. Inside the Solution class, create a public static ReadFileThread class that implements the ReadFileInterface interface (Think about what is more appropriate: Thread or Runnable).
3.1. The setFileName method must set the name of the file whose contents will be read.
3.2. The getFileContents method must return the contents of the file.
3.3. In the run method, read the contents of the file and close the stream. Separate the lines of the file with spaces.
4. Think about where you need to wait for the thread to finish to ensure that the files are displayed sequentially.
4.1. To do this, add a call to the appropriate method.

Expected output:
[entire contents of the first file] [entire contents of the second file]

Requirements:

The Solution class's static block should read from the console the names of two files and store them in the variables firstFileName and secondFileName.
In the Solution class, declare the public static ReadFileThread class.
The ReadFileThread class must implement the ReadFileInterface interface.
The ReadFileThread class must inherit the appropriate class.
The ReadFileThread class's run method should read lines from the file set by the setFileName method. And the getFileContents method of this same class must return the file contents. The return value is one string consisting of the lines of the file, separated by spaces.
The systemOutPrintln method must call the join method on the created object f.
The program's output should consist of 2 lines. Each line contains the contents of one file.

package com.codegym.task.task16.task1630; import java.io.*; import java.util.ArrayList; public class Solution { public static String firstFileName; public static String secondFileName; static { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); try { firstFileName = reader.readLine(); secondFileName = reader.readLine(); } catch (IOException e) { } } public static void main(String[] args) throws InterruptedException { systemOutPrintln(firstFileName); systemOutPrintln(secondFileName); } public static void systemOutPrintln(String fileName) throws InterruptedException { ReadFileInterface f = new ReadFileThread(); f.setFileName(fileName); f.start(); f.join(); System.out.println(f.getFileContent()); } public interface ReadFileInterface { void setFileName(String fullFileName); String getFileContent(); void join() throws InterruptedException; void start(); } public static class ReadFileThread extends Thread implements ReadFileInterface { String fullFileName; String stringStart; String stringFinish = ""; ArrayList<String> list = new ArrayList<>(); @Override public void setFileName(String fullFileName) { this.fullFileName = fullFileName; } public void run() { try { FileInputStream fileInputStream = new FileInputStream(fullFileName); BufferedReader reader = new BufferedReader(new InputStreamReader(fileInputStream)); while ((stringStart = reader.readLine()) != null) { list.add(stringStart); } reader.close(); fileInputStream.close(); } catch (FileNotFoundException e) { } catch (IOException e) { } } @Override public String getFileContent() { for (String stringFromList : list) { stringFinish = stringFinish + " " + stringFromList; stringFinish.trim(); } return stringFinish.trim(); } } }

Comments (14)

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nickyy

Level 18 , Diou, France

24 September 2020, 09:30

You could simplify your code significantly by having the run method look like that:

@Override
public void run() {
    try {
        BufferedReader reader = new BufferedReader(new FileReader(new File(fileName)));
        fileContent = reader.lines().collect(Collectors.joining(" "));
        reader.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

With fileContent being a class declared String.

Juanf Software Developer at EPAM

5 October 2019, 19:31

Can anyone tell me why that way of comparing a String is valid (with != instead of .equal)?:

while ((stringStart = reader.readLine()) != null) {
                   list.add(stringStart);
               }

shouldn't it be like this?:

while ((!(stringStart = reader.readLine()).equals(null))) {
                    list.add(stringStart);
                }

Darko Jakimovski

Level 18 , Kriva Palanka, Macedonia, The Former Yugoslav Republic of

29 May 2019, 13:02

public String getFileContents() {
            if (list.isEmpty()) return "";
            String toReturn = "";
            for (String s : list) {
                toReturn += s + " ";
            }
            return toReturn;
        }

Nothing fancy, just wanted to share. Everything else is give or take the same. Salute.

Guadalupe Gagnon

Level 37 , Tampa, United States

7 May 2019, 18:10

Try removing the .trim from line 75 and remove line 73. By trimming it could be removing space characters that are actually in place on purpose from the lines read in. I don't know if that is the issue or not, does the mentor give any advice?

Ramilya

Level 20 , SPb, Russian Federation

7 May 2019, 18:24

If I delete trim, there is space before lines in output... For example: " 1 1 1 1" Can you recommend how can I avoid this space any another ways?

Guadalupe Gagnon

Level 37 , Tampa, United States

7 May 2019, 18:53

This is what I do. The only problem is the first entry. Do that one first before you start looping so that you can add it with no leading space. Then make a loop that adds a space plus each new line starting at the second entry:

public String getFileContent() {
   stringFinish = list.get(0);
   for (int i =1; i < list.size(); i ++)
      stringFinish = stringFinish + " " + list.get(i);

   return stringFinish;
}

Ramilya

Level 20 , SPb, Russian Federation

7 May 2019, 19:40

Thanks! But again output is correct and there is the mistake in Requirement No.6...

Guadalupe Gagnon

Level 37 , Tampa, United States

7 May 2019, 20:28

how about this: getFileContents() <-- with an 's' change that at lines 36 and 70

Ramilya

Level 20 , SPb, Russian Federation

8 May 2019, 15:31

Doesn't help...

Guadalupe Gagnon

Level 37 , Tampa, United States

8 May 2019, 15:47

What does your code look like now?

Ramilya

Level 20 , SPb, Russian Federation

9 May 2019, 10:32

It's ReadFileThread class.

public static class ReadFileThread extends Thread implements ReadFileInterface {
    String fullFileName;
    String stringStart;
    String stringFinish = "";
    ArrayList<String> list = new ArrayList<>();

    @Override
    public void setFileName(String fullFileName) {
        this.fullFileName = fullFileName;
    }

    public void run() {

        try {
            FileInputStream fileInputStream = new FileInputStream(fullFileName);
            BufferedReader reader = new BufferedReader(new InputStreamReader(fileInputStream));
            while ((stringStart = reader.readLine()) != null) {
                list.add(stringStart);
            }
            reader.close();
            fileInputStream.close();
        } catch (FileNotFoundException e) {
        } catch (IOException e) {
        }
    }

    @Override
    public String getFileContents() {
        stringFinish = list.get(0);
        for (int i =1; i < list.size(); i ++)
            stringFinish = stringFinish + " " + list.get(i);

        return stringFinish;
    }
}

Guadalupe Gagnon

Level 37 , Tampa, United States

9 May 2019, 13:28

try this: in the above code, change lines 15-16 to:

FileReader fileInputStream = new FileReader(fullFileName);
BufferedReader reader = new BufferedReader(fileInputStream);

You wont need to change anything else in your code because this will still function the same. I am thinking that the InputStreamReader may be causing the problem. I don't know for sure. When the code works exactly as it is supposed to according to task conditions, then there is most likely 1 of 2 things (or both) that are causing verification failure: 1) some small spelling error, or 2) some unnecessary code or over complicated code. I though for sure that adding the s on the end of getFileContents would pass you, but that didn't happen...... so now its option 2, which is a lot harder to diagnose and find a solution.

Guadalupe Gagnon

Level 37 , Tampa, United States

9 May 2019, 13:40

useful

Here is my suggestion for the ReadFileInterface:

public static class ReadFileThread extends Thread implements ReadFileInterface {
        String fullFileName;
        ArrayList<String> list = new ArrayList<>();

        @Override
        public void setFileName(String fullFileName) {
            this.fullFileName = fullFileName;
        }

        public void run() {
            try {
                FileInputStream fileInputStream = new FileInputStream(fullFileName);
                BufferedReader reader = new BufferedReader(new InputStreamReader(fileInputStream));

                while (reader.ready())
                    list.add(reader.readLine());

                reader.close();
                fileInputStream.close();
            } catch (IOException e) { }
        }

        @Override
        public String getFileContent() {
            if(list.isEmpty()) return "";
            String stringFinish = list.get(0);

            for (int i = 1; i < list.size(); i++)
                stringFinish = stringFinish + " " + list.get(i);

            return stringFinish;
        }
    }

I just removed the 2 strings you were using as class properties, stringStart and stringFinish. The first you can do without as the BufferedReader class has a method that returns true/false depending on whether there is more data to read in (BufferedReader.ready(), used on line 15). The stringFinish variable I just made a local variable in the getFileContents() class, used exactly as you were using it prior. Also added a check to the getFileContents that returns a blank string if the list is empty.

Ramilya

Level 20 , SPb, Russian Federation

10 May 2019, 16:44

It works. Thank you very much!