Hints required: sequential vs parallel

Question about the task

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Java Core, Level 6, Lesson 13

Under discussion

1. In the Solution class, create a public static Read3Strings class that inherits Thread.
2. In the run method, read three lines from the console.
3. Three lines should be read in succession on one thread and combined into one space-delimited string.
4. In the main method, display the result for each thread.
5. Use join.

Example:

Input:
a b c d e f

Output:
a b c d e f

Requirements:

In the Solution class, declare the public static Read3Strings class.
The Read3Strings class should inherit the Thread class.
The Read3Strings class's run method must read three lines.
The Read3Strings class must have a public printResult method.
The printResult method should display the 3 read lines, separating them with spaces.
The main method should call the created threads' start methods.
The main method should call the created threads' join methods.
The program's output should indicate that the threads read the lines sequentially, not in parallel.

package com.codegym.task.task16.task1629; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; public class Solution { public static volatile BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); static String word1, word2,word3; public static void main(String[] args) throws InterruptedException { Read3Strings t1 = new Read3Strings(); Read3Strings t2 = new Read3Strings(); //write your code here t1.start(); t2.join(); // t1.join(); t2.start(); t1.join(); // t1.start(); // t2.join(); t1.printResult(); t2.printResult(); } //write your code here public static class Read3Strings extends Thread { public void run() { // String word1, word2,word3; try{ word1=reader.readLine(); word2=reader.readLine(); word3=reader.readLine(); } catch(IOException e) { } } public void printResult() { System.out.print(word1+" "); System.out.print(word2+" "); System.out.println(word3+" "); } } }

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Patryk

Level 24 , Warsaw, Poland

29 December 2019, 17:38

I wouldn't write array as a public and static cause it doesn't meet encapsulation principle and simply you don't need this :)

package com.codegym.task.task16.task1629;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class Solution {
    public static volatile BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws InterruptedException {
        Read3Strings t1 = new Read3Strings();
        Read3Strings t2 = new Read3Strings();

        //write your code here
        t1.start();
        t1.join();
        t2.start();
        t2.join();


        t1.printResult();
        t2.printResult();
    }

    public static class Read3Strings extends Thread {
        private List<String> stringList = new ArrayList<>();
        private int count = 0;

        @Override
        public void run() {
            while (count < 3) {
                try {
                    stringList.add(reader.readLine());
                    count++;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        public void printResult() {
            for (String x : stringList) {
                System.out.print(x + " ");
            }
            System.out.println();
        }

    }

}

Salim

Level 26 , Bukhara, Uzbekistan

23 November 2019, 09:22

package com.codegym.task.task16.task1629; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.concurrent.atomic.AtomicInteger; public class Solution { public static volatile BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); //public static volatile AtomicInteger prntcount = new AtomicInteger(0); public static ArrayList<String> arrlist = new ArrayList<>(); public static String str[] = new String[5]; public static void main(String[] args) throws InterruptedException { Read3Strings t1 = new Read3Strings(); t1.start(); t1.printResult(); t1.join(); Read3Strings t2 = new Read3Strings(); t2.start(); t2.join(); t2.printResult(); //write your code here str = arrlist.toArray(str); } public static class Read3Strings extends Thread { public void run() { try { for (int i = 0; i < 3; i++) { arrlist.add(reader.readLine()); } } catch (Exception e) {} } public void printResult() { for (int j = 0; j < arrlist.size(); j++) { System.out.print(arrlist.get(j) + " "); } System.out.println(); } } //write your code here }

Kateřina Fořtová

Level 24 , Czech Republic

23 August 2019, 15:13

this works: Read3Strings t1 = new Read3Strings(); t1.start(); t1.printResult(); t1.join(); Read3Strings t2 = new Read3Strings(); t2.start(); t2.join(); t2.printResult();

Yuchen

Level 17 , Los Angeles, America

26 August 2019, 00:19

Actually it still cannot pass the last condition

Yuchen

Level 17 , Los Angeles, America

26 August 2019, 00:22

It should be: Read3Strings t1 = new Read3Strings(); t1.start(); t1.join(); t1.printResult(); Read3Strings t2 = new Read3Strings(); t2.start(); t2.join(); t2.printResult();

Boris the Llama

Level 20 , Maidstone, United Kingdom

14 August 2019, 18:41

Try; t1.start(); t1.printResult(); t1.join(); t2.start(); t2.printResult(); t2.join();

Rupa Joshi

Level 29 , Tokyo, Japan

29 July 2019, 08:44

I think sequentially means you should start t1 and then join the t1 and then print1 and then start t2 is in sequential manner and when both the threads starts then they run in parallel.In your case you have started t1 and saying join t2 when t2 starts later. has it not thrown any error as t2 has not even started. I am not sure I am just thinking. Hope it works.

hidden #10465081

Level 24

10 July 2019, 11:15

getting the same validation error as you, looking forward to someone helping us