I don't understand the recommendation

Question about the task

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Could you explain what the following recommendation from mentor means: "Be sure that the getFileContents method returns an empty string if the run method has not been started."? What should I change in my code? I've tried this, but it doesn't work:

public String getFileContents(){
            if (!isAlive()){
                return "";
            } else{
                return fileContents;
            }
        }

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.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.io.InputStreamReader; public class Solution { public static String firstFileName; public static String secondFileName; static { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); try{ firstFileName = br.readLine(); secondFileName = br.readLine(); br.close(); } catch (IOException e){ e.getMessage(); } } 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.getFileContents()); } public interface ReadFileInterface { void setFileName(String fullFileName); String getFileContents(); void join() throws InterruptedException; void start(); } public static class ReadFileThread extends Thread implements ReadFileInterface{ private String fileName; private String fileContents; public void setFileName(String fullFileName) { this.fileName = fullFileName; } public String getFileContents(){ return fileContents; } public void run(){ try { BufferedReader br = new BufferedReader(new FileReader(this.fileName)); while (br.ready()) { String line = br.readLine(); fileContents += line + " "; } br.close(); } catch (IOException e){ e.getMessage(); } } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

20 April 2019, 14:55

Try making a class property boolean set to false. In the run method, when the file has been downloaded completely set it to true. Then use that flag to either return a blank string or the file contents.

Zbigniew

Level 23 , Dabrowa Tarnowska, Poland

23 April 2019, 08:27

I've tried your idea, but i don't know if i did it the right way. The code below shows recomendation from mentor: "Be sure that the getFileContents method returns only the file contents, and does not add anything extra to it." (unsatisfied fifth condition) The code:

public static class ReadFileThread extends Thread implements ReadFileInterface{
        private String fileName;
        private String fileContents;
        private boolean isDownloaded = false;

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

        public String getFileContents(){
            if (!isDownloaded) return "";
             else return fileContents;
        }

        public void run(){
            try {
                BufferedReader br = new BufferedReader(new FileReader(this.fileName));

                while (br.ready()) {
                    String line = br.readLine();
                    fileContents += line + " ";
                }
                br.close();

            } catch (IOException e){ e.getMessage(); }
            this.isDownloaded = true;
        }
    }
}

Guadalupe Gagnon

Level 37 , Tampa, United States

23 April 2019, 13:10

Try line 26 inside the try block. If an error occurs while downloading then you don't want the isDownloaded to be true.

Azja

Level 32 , Krakow, Poland

20 April 2019, 11:20

solution

Maybe you should set fileContents to "" immediately in line 52

Zbigniew

Level 23 , Dabrowa Tarnowska, Poland

23 April 2019, 08:19

It worked! Thank you.