Andrej Sol | OS - Volleyball Tournament | Septemvri 2019

import java.util.HashSet;
import java.util.concurrent.Semaphore;

public class VolleyballTournament {


    static Semaphore sala = null;
    static Semaphore soblekuvalna = null;
    static int count = 0;
    static Semaphore cLock = null;
    static Semaphore canPlay = null;

    public static void init() {
        sala = new Semaphore(12);
        soblekuvalna = new Semaphore(4);
        cLock = new Semaphore(1);
        canPlay = new Semaphore(0);
    }

    public static class Player extends TemplateThread{


        public Player(int numRuns) {
            super(numRuns);
            // TODO Auto-generated constructor stub
        }

        public void execute() throws InterruptedException {
            // at most 12 players should print this in parallel
            sala.acquire();
            System.out.println("Player inside.");
            // at most 4 players may enter in the dressing room in parallel
            soblekuvalna.acquire();
            cLock.acquire();
            count++;
            System.out.println("In dressing room.");
            Thread.sleep(10);// this represent the dressing time
            if(count==4) {
                canPlay.release(4);
                soblekuvalna.release(4);
                count=0;
            }
            cLock.release();
            canPlay.acquire();

            // after all players are ready, they should start with the game together
            System.out.println("Game started.");
            Thread.sleep(100);// this represent the game duration
            System.out.println("Player done.");
            sala.release();
            cLock.acquire();
            count--;
            if(count==1) {
                System.out.println("Game finished.");
            }
            // only one player should print the next line, representing that the game has finished
            cLock.release();
        }
    }



    public static void main(String[] args) throws InterruptedException {
        HashSet<Player> threads = new HashSet<>();
        for (int i = 0; i < 60; i++) {
            Player p = new Player(i);
            threads.add(p);
        }
        // run all threads in background
        init();
        for(Player t : threads) {
            t.start();
        }
        // after all of them are started, wait each of them to finish for maximum 2_000 ms
        for(Player t : threads) {
            t.join(2_000);
            //t.interrupt(); HACK
        }
        // for each thread, terminate it if it is not finished
        for(Player t : threads) {
            if(t.isAlive()) {
                t.interrupt();
                System.out.println("Possible deadlock!");
            }
        }
        System.out.println("Tournament finished.");

    }
}