Variable in while loop from run() method

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Hi, I deleted last request because I didn't knew how to edit it. AzjaLevel 30 , Krakow 36 minutes ago Your code is working fine and "end" variable is updated but it is recommended to use "StringBuilder class" for string concatenation and it should use "getFileContents method" in "run method" because now this code doesn't use created thread. Also you don't have to override "start method" because it's already overridden from inheriting "Thread class". P.S: There is useful method with working with String when you have additional spaces at the end of the line called "trim". It just remove additional spaces from the end and from the beginning. There is how it works https://www.tutorialspoint.com/java/java_string_trim.htm Reply gmb55Level 18 , Krakow 3 minutes ago Ok, but how about now? When I put it in run() to get Threads it dosen't work.

"C:\Program Files\Java\jre\bin\java.exe" -Dfile.encoding=windows-1250 -jar D:\Programowanie\Aplikacje\test_java\out\artifacts\test_java_jar\test_java.jar
null
null
Process finished with exit code 0

There is null, because this doesn't update end variable from while loop in run() method. And I don't know why :/

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.*; public class Solution { public static String firstFileName; // = "C:\\Users\\micha\\Documents\\1.txt"; public static String secondFileName; // = "C:\\Users\\micha\\Documents\\2.txt"; //write your code here static { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); try { firstFileName = reader.readLine(); secondFileName = reader.readLine(); } catch (IOException e) { e.printStackTrace(); } } public static void main(String[] args) throws InterruptedException, IOException { systemOutPrintln(firstFileName); systemOutPrintln(secondFileName); } public static void systemOutPrintln(String fileName) throws InterruptedException, IOException { ReadFileInterface f = new ReadFileThread(); f.setFileName(fileName); f.start(); f.join(); //write your code here System.out.println(f.getFileContents()); } public interface ReadFileInterface { void setFileName(String fullFileName); String getFileContents() throws IOException; void join() throws InterruptedException; void start(); } //write your code here public static class ReadFileThread extends Thread implements ReadFileInterface { String fullFileName; private String end; @Override public void setFileName(String fullFileName) { this.fullFileName = fullFileName; } @Override public void start() { } @Override public void run() { try { FileReader file = new FileReader(fullFileName); BufferedReader reader = new BufferedReader(file); while (reader.ready()) { String print = reader.readLine(); end += print + " "; } reader.close(); } catch (Exception e) { } } @Override public String getFileContents() throws IOException { return end; } } }

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Azja

Level 32 , Krakow, Poland

19 August 2019, 09:02

Now you get null because code in systemOutPrintln method just call getFileContents method and this method return "end" variable which is not updated, and remove start method from ReadFileThread class

Azja

Level 32 , Krakow, Poland

19 August 2019, 08:55

useful

Try like this "getFileContents":

@Override
        public String getFileContents() throws IOException {

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

            while (reader.ready()) {
                String print = reader.readLine();
                end += print + " ";

            }
            reader.close();

            return  end.trim();
        }

I used "trim()" it's removing last unnecessary space from the end of the string But I recommended to use String builder

@Override
       public String getFileContents() throws IOException {

           FileReader file = new FileReader(fullFileName);
           BufferedReader reader = new BufferedReader(file);
           StringBuilder builder = new StringBuilder();

           while (reader.ready()) {
               String print = reader.readLine();
               builder.append(print).append(" ");
           }
           reader.close();

           return  builder.toString().trim();
       }

And "run":

@Override
        public void run() {
            try {
                System.out.println(getFileContents());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

and just start new thread like this in systemOutPrintln method:

public static void systemOutPrintln(String fileName) throws InterruptedException, IOException {
       ReadFileInterface f = new ReadFileThread();
       f.setFileName(fileName);
       f.start();
       f.join();
   }

gmb55

Level 25 , Tarnów, Poland

19 August 2019, 09:20

Dzięki :) Everything was OK, I had to add only one variable to run() method . Now it looks like:

public void run() {
String print = "";
    try {
    FileReader file = new FileReader(fullFileName);
    BufferedReader reader = new BufferedReader(file);

    while (reader.ready()) {
      String start = reader.readLine();
        print += start + " ";
    }
    end = print;
} catch (Exception e) {}}

If I used "end" directly in whlie loop it wasn't updated. PS. Thanks for trim(), I didn't knew it before.

Azja

Level 32 , Krakow, Poland

19 August 2019, 09:58

Nie ma sprawy :D