I am probably overthinking this question....

Question about the task

Under discussion

Appreciate if you could point me in the right direction. Thanks in advance.

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 Thread current = this.currentThread(); try { while (!current.isInterrupted()) { result.add(reader.readLine()); readStringCount.set(readStringCount.incrementAndGet()); } } catch (IOException e) { e.printStackTrace(); } readStringCount.set(0); } @Override public String toString() { return result.toString(); } } }

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Gellert Varga

Level 23 , Szekesfehervar, Hungary

2 September 2021, 11:00

P.s.1: Since threads are a more complicated topic for me too, and I'm not 100% sure if I said everything right, I'd appreciate your feedback. Even if you can pass the task, and even if you still have problems with it. Thank you:) P.s.2: I don't use IntelliJ IDE, I use an online IDE. And I'm not using it in interactive mode. So the readLine() command is not waiting for me while I type the strings. Instead, I write the whole input list (in this case 5 1 2 3 4 5) into the input field in advance, and then the program reads them from there. (This may be necessary to understand why the program reads so many nulls in my testing.)

Gellert Varga

Level 23 , Szekesfehervar, Hungary

2 September 2021, 10:52

0.) I think point IV will be the most important. I) I tried the program, it worked. So I don't quite understand why there was a red question mark next to all the requirements. I thought it only happens when JVM can't compile the prg. This is just a guess: maybe you should try change this code: Thread current = this.currentThread(); to this code: Thread current = Thread.currentThread(); In a previous task, they specifically requested that currentThread() be created statically on Thread rather than on 'this'. Unfortunately, I don't know what the significant difference between the two versions is, but that may be why the validator is stuck. Maybe there is no difference, I don't know. But I would try to replace this line. - I would be happy if a more experienced student than me, if she/he reads this, would give his opinion on this:) II) I ran your program 2 times and got the following outputs: #1:[1, 3, 4, , null] #2:[2, 5, null] #3:[] #1:[1, 2, 3, 4, 5, , null, null, null, null, null] #2:[] #3:[null, null, null] And my own program (which passed) now gives me outputs like this: #1:[1, 2, 3, 4, 5, ] #2:[] #3:[] #1:[1, 3, 5] #2:[2, 4, ] #3:[] From this you can see the difference. When the JVM is executing thread1 or thread3, and has not yet jumped back to the main thread to continue the while cycle and give the interrupt, the thread can continue the read cycle for a long time, longer than the specified 5. I added a condition to the read, that if it reads a null, it should not put it in the list. III) This is an unnecessarily over-complicated command: readStringCount.set(readStringCount.incrementAndGet()); Instead, it is sufficient to write this: readStringCount.incrementAndGet(); // this will increment the value by 1, too. IV) In line 56, the set(0) command is, in my opinion, a misstep. Because our goal is to count the number of lines read by all threads, so each thread should increment this common variable by 1! I think it should never be reset to zero.