CodeGym/Help with Java Tasks/Dear Lord Jesus, what have I done to deserve this punishm...

Level 41

14.12.2020
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Dear Lord Jesus, what have I done to deserve this punishment? Why isn't it validating the first requirement?

Question about the task

Resolved

Pleeeaseeeeeeeeee

Figure out what the program does.
Implement the calculateHorsesFinished method.
It must:
1. Calculate and return the number of horses that have finished. Use the isFinished() method.
2. If a horse has not yet crossed the finish line (!IsFinished()), then:
2.1. Display "Waiting for " + horse.getName().
2.2. Wait until it finishes the race. Think about what method you need to use to do this.
2.3. Not treat such a horse as finished.

Requirements:

The calculateHorsesFinished method must return the number of horses that have finished.
The calculateHorsesFinished method must call the isFinished method on each horse in the passed list.
If any of the horses in the passed list has not yet finished, then the calculateHorsesFinished method should display "Waiting for " + horse.getName(). Example output for the first horse: "Waiting for Horse_01".
If any of the horses in the passed list has not yet finished, then the calculateHorsesFinished method must wait until it finishes. Use the correct method for waiting.
After the program is finished, the console must indicate that all the horses have finished. Example output for the first horse: "Horse_01 has finished the race!".

package com.codegym.task.task16.task1607; import java.util.ArrayList; import java.util.List; /* Horse racing */ public class Solution { public static void main(String[] args) throws InterruptedException { List<Horse> horses = prepareHorsesAndStart(10); while (calculateHorsesFinished(horses) != horses.size()) { } } public static int calculateHorsesFinished(List<Horse> horses) throws InterruptedException { int finishedCount = 0; //write your code here for (; finishedCount < horses.size(); finishedCount++) { if (!horses.get(finishedCount).isFinished()){ System.out.println("Waiting for " + horses.get(finishedCount).getName()); horses.get(finishedCount).join(); } } return finishedCount; } public static List<Horse> prepareHorsesAndStart(int horseCount) { List<Horse> horses = new ArrayList<>(horseCount); String number; for (int i = 1; i < horseCount + 1; i++) { number = i < 10 ? ("0" + i) : "" + i; horses.add(new Horse("Horse_" + number)); } for (int i = 0; i < horseCount; i++) { horses.get(i).start(); } return horses; } public static class Horse extends Thread { private boolean isFinished; public Horse(String name) { super(name); } public boolean isFinished() { return isFinished; } public void run() { String s = ""; for (int i = 0; i < 1001; i++) { // Delay s += "" + i; if (i == 1000) { s = " has finished the race!"; System.out.println(getName() + s); isFinished = true; } } } } }

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Nouser

Level 36 , Germany

14 December 2020, 11:04

solution

Try to validate with my code to see if it is really the calculateHorsesFinished method or if the problem is somewhere else. Your version of the method should work though.

for (Horse horse : horses) {
    if (horse.isFinished())
        finishedCount++;
    else {
        System.out.println("Waiting for " + horse.getName());
        horse.join();
    }
}

Andrei

Level 41

14 December 2020, 13:51

Yes, it worked with your code. I tried to understand the difference between your and mine but I can't quite see it. Is there a difference?

Nouser

Level 36 , Germany

14 December 2020, 14:05

For me yours and mine are equal. So I assumed it is the validator that just didn''t like yor loop or whatever.

Dave Shapiro

Level 31 , Co. Kerry , Ireland

17 December 2020, 14:38

Possibly a typo - the semicolon after opening bracket of the for loop, line 22?

Andrei

Level 41

18 December 2020, 17:47

But isn't that mandatory in a for loop even if you leave that field empty?

Dave Shapiro

Level 31 , Co. Kerry , Ireland

18 December 2020, 18:31

I just looked it up - you are correct! Sorry, I'm new to coding, didn't realise you could do that. Learn something new every day :)

Andrei

Level 41

18 December 2020, 19:06

No problem! :)

Guadalupe Gagnon

Level 37 , Tampa, United States

18 December 2020, 19:23

useful

Its very subtle, but there is a minor difference between the codes: Andrei's version increases the count every single loop cycle Nouser's version increases the count only when the horse is finished. This means that Andrei's version will return 10 every single time it is called in main while Nouser's version will return 10 minus the number of horses it it waiting on the first time and then 10 the second time. You can see this if you modify the code:

public static List<Horse> prepareHorsesAndStart(int horseCount) {
   // code
   System.out.println(finishedCount);
   return finishedCount;
}

And run it with both versions. Now as to why the validation doesn't like Andrei's code I couldn't say. It does exactly as it is supposed to do according to the task conditions.

Oliver Heintz

Level 18 , Mustang, United States

26 January 2021, 02:42

This fixed my problem, too. I always test my code before submitting, but the validation didn't like it the first FOUR times. I kept making subtle changes trying to figure out what was going on, and it was because I was iterating in an else statement, figuring that if I was waiting already, I should just go ahead an iterate.

Michael

Level 23 , Madrid, Spain

28 November 2021, 12:59

In my case I had to pay special attention between calling:

horse.isFinished

and calling:

horse.isFinished()