CodeGym/Help with Java Tasks/Requirements are met, data is randomly stored in each thr...

Level 41

04.01.2021
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Requirements are met, data is randomly stored in each thread and displayed, yet not passing verification. Help pls!

Question about the task

Under discussion

If I introduce 3 and bing, bang, bong, the results are randomly stored in each list and they vary in storage every time. Yet it is not correct. Furthermore, if I introduce 0 or a negative number, the program terminates immediately. Therefore, what am I doing wrong?

1. Figure out what the program does.
1.1. Each thread should read lines from the console. Use the existing static BufferedReader reader.
1.2. Use AtomicInteger readStringCount to calculate how many lines all the threads have read from the console.
2. Implement the run method:
2.1. As long as a thread is not interrupted (!IsInterrupted), read lines from the console and add them to List<String> result.
2.2. Use readStringCount to count the strings read from the console.

Requirements:

The run method must run until the thread is terminated (!IsInterrupted).
The run method must NOT create its own InputStreamReaders or BufferedReaders.
The run method must read words from the reader and add them to the result list.
After each string is read, the run method must increment readStringCount by 1.
The program should display the data read by each thread.

package com.codegym.task.task16.task1628; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List; import java.util.concurrent.atomic.AtomicInteger; public class Solution { public static volatile AtomicInteger readStringCount = new AtomicInteger(0); public static volatile BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); public static void main(String[] args) throws IOException { // Read string count int count = Integer.parseInt(reader.readLine()); // Init threads ReaderThread consoleReader1 = new ReaderThread(); ReaderThread consoleReader2 = new ReaderThread(); ReaderThread consoleReader3 = new ReaderThread(); consoleReader1.start(); consoleReader2.start(); consoleReader3.start(); while (count > readStringCount.get()) { } consoleReader1.interrupt(); consoleReader2.interrupt(); consoleReader3.interrupt(); System.out.println("#1:" + consoleReader1); System.out.println("#2:" + consoleReader2); System.out.println("#3:" + consoleReader3); reader.close(); } public static class ReaderThread extends Thread { private List<String> result = new ArrayList<>(); public void run() { //write your code here String line = ""; while (!currentThread().isInterrupted()) { try { line = reader.readLine(); result.add(line); readStringCount.getAndIncrement(); } catch (IOException e) { e.printStackTrace(); } } } @Override public String toString() { return result.toString(); } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

4 January 2021, 15:38

Try removing: e.printStackTrace();

Andrei

Level 41

4 January 2021, 15:55

Nop, same result.

Guadalupe Gagnon

Level 37 , Tampa, United States

4 January 2021, 16:15

try:

while(!isInterrupted()){
   // rest of code
}

Andrei

Level 41

4 January 2021, 16:22

Yup, already had that modified, thought also that might be, but not, same result.

public static class ReaderThread extends Thread {
       private List<String> result = new ArrayList<>();

       public void run() {
           //write your code here
           String line = "";
           while (!isInterrupted()) {
               try {
                   line = reader.readLine();
                   result.add(line);
                   readStringCount.incrementAndGet();
               } catch (IOException e) {
                  // e.printStackTrace();
               }
           }
           readStringCount.set(0);
       }

Guadalupe Gagnon

Level 37 , Tampa, United States

4 January 2021, 16:34

Remove line 16 of that code. Also you can try testing that the String is not null before adding it to the result and incrementing the counter?

Andrei

Level 41

4 January 2021, 16:35

public static class ReaderThread extends Thread {
        private List<String> result = new ArrayList<>();

        public void run() {
            //write your code here
            String line = "";
            while (!isInterrupted()) {
                try {
                    line = reader.readLine();
                    result.add(line);
                    readStringCount.incrementAndGet();
                } catch (IOException e) {
                   // e.printStackTrace();
                }
            }
            //readStringCount.set(0);
        }
        @Override
        public String toString() {
            return result.toString();
        }
    }

Andrei

Level 41

4 January 2021, 16:35

Andrei

Level 41

4 January 2021, 16:36

The replies are to your previous, bigger comment, which I think you have edited

Andrei

Level 41

4 January 2021, 16:47

What I understand from the requirement is that each thread should store the same amount of strings. For example if I introduce 3, then each thread should store 3 strings. That's why I also added the counter reset on line 16 to take this into consideration. I tried adding

if (line.equals("")) break;

between lines 9 and 10 but did not work, it did not break out of the while loop. So I assume it is not correct?

Andrei

Level 41

4 January 2021, 15:25

Here is an updated version of the program but still not passing. I have only included the ReaderThread class :

public static class ReaderThread extends Thread {
        private List<String> result = new ArrayList<>();

        public void run() {
            //write your code here
            String line = "";
            while (!(currentThread().isInterrupted())) {
                try {
                    line = reader.readLine();
                    result.add(line);
                    readStringCount.incrementAndGet();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            readStringCount.set(0);
        }

Nouser

Level 36 , Germany

4 January 2021, 16:34

try putting the while loop inside of the try block or, as an alternative, replace e.printStackTrace(); with interrupt(); //or to get used to it (cause a lot of times you'll work with Runnable and here you can not access Thread methods directly) Thread.currentThread().interrrupt(); Edit: forget setting the interrupt again in the catch block... we have here no sleep() and hence no catching of InterruptedException... go with moving the while loop inside try

Andrei

Level 41

4 January 2021, 16:44

Nope, same errors as before, have tried putting the while loop inside the try. Furthermore, have tried with interrupt as well.

public static class ReaderThread extends Thread {
        private List<String> result = new ArrayList<>();

        public void run() {
            //write your code here
            String line = "";
                try {
                    while (!isInterrupted()) {
                    line = reader.readLine();
                    result.add(line);
                    readStringCount.incrementAndGet();}
                } catch (IOException e) {
                   // e.printStackTrace();
                }
            //readStringCount.set(0);
        }
        @Override
        public String toString() {
            return result.toString();
        }
    }

Andrei

Level 41

4 January 2021, 16:45

Nouser

Level 36 , Germany

4 January 2021, 17:14

No, it should run the threads as long as count hasn't been reached and then print the inputs of the three threads. And most probably the amounts of read strings are diffent. What does the mentor suggest? And my solution isn't that different. I additionally just check for null, however that shouldn't matter at all. My last idea would be to change the interrupted check to something more general. But isInterrupted() should work here without problem

Thread currentThread = Thread.currentThread();
while(!currentThread.isInterrupted()) {

in the end that should verify...

public void run() {
    while(!isInterrupted()) {
        try {
            result.add(reader.readLine());
            readStringCount.getAndIncrement();
         } catch (IOException ioe) {/* ignore */}
    }
}