Why does this not validate?

Starting a Thread with the run() is the incorrect way of doing it. A thread should always be started with the start() method. The reason is that the start() method creates a new thread that will call the run() method, and this thread will run separately from the primary thread created with the start of the program. Take this code for example:

public class Solution {
    public static void main(String[] args) throws Exception {
        Thread thread1 = new Thread(new SpecialThread());
        String[] x = {"Starting thread with run", "Reached", "Successfully Interrupted"};

        System.out.println(x[0]);
        thread1.run();
        System.out.println(x[1]);
        Thread.sleep(3000);
        thread1.interrupt();
        System.out.println(x[2]);

        /*System.out.println(x[0]);
        thread1.start();
        System.out.println(x[1]);
        Thread.sleep(3000);
        thread1.interrupt();
        System.out.println(x[2]);*/
    }

    public static class SpecialThread implements Runnable {
        public void run() {
            while(true){
                try {
                    System.out.println("This is the run method inside SpecialThread");
                    Thread.sleep(250);
                }catch (Exception e){
                    break;
                }
            }
        }
    }
}

In the main method the code uses run() to start the thread. Line 6 will never be reached because the programs primary thread is directed to the run() method and gets stuck in an infinite loop. If you comment out lines 6-11 and uncomment the others, re-run the program, and compare results you will see that the "Reached" line is output and the program runs for +/- 3 seconds as intended before the interrupt() is called and ends the program. This is because a new thread is created for the lines in the run() method that ran separately from the primary thread that started the program.

You gave me the answer, I wasn't suppose to start the threads. When I took that out, it validated both ways. Thanks.

I wasn't sure what was wrong because the requirements are not clear, so I just compared our code for differences. Some problems are really bad, and you will be spending more time trying to figure out what the requirements mean rather than actually writing code.

I've definitely gotten more frustrated in levels 11+ with the lessons/challenge requirements. Still thankful for the program, but CodeGym has a few screws left to tighten

I made the same mistake and started the threads. The way it is worded makes you think you have to start them.

Guadalupe, i think that i love you <3 You are the Pope here.

If I write:

SpecialThread a = new SpecialThread();
Thread b = new Thread(a);
list.add(b);

will not verify So it is right:

Thread a = new Thread(new SpecialThread();
list.add(a);

It is a bit annoying

How are you able to pass an argument inside of new Thread() ? ex. new Thread(new SpecialThread()) ; ? Shouldn't new Thread () ; be the only accepted version? After all, you did not overload the constructor to make it possible to pass a SuperThread object to it.

@Andrei The Thread class has multiple constructors. One is a default constructor (a constructor with no arguments), and another one is a constructor that takes a Runnable object. There are more but those are in the scope of this task. The SpecialThread class in this code, a custom class created by codegym for "us", implements the Runnable interface, which means any objects of SpecialThread are also objects of Runnable. Therefore the Thread constructor can take a SpecialThread object as a Runnable. You could also create your own custom class that implement Runnable, to do anything that you want it to do, and pass it to the Thread class. You would just need to ensure that the class that implements Runnable has a run() method, which IntilliJ would give you a red squiggly until you do so.

Ah yes, I have opened the oracle article about thread... here I dive in the pits of hell once more... lol

You are sounding more and more like a professional programmer every day

lol, thanks!