ОС - Tennis Tournament

package ispiti.tennisTournament;

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

public class TennisTournament {

    static Semaphore redPlayers;
    static Semaphore greenPlayers;
    static int numPlayers;
    static Semaphore protect;
    static Semaphore canPlay;
    static Semaphore finishedPlaying;

    public static void init(){
        redPlayers = new Semaphore(2);
        greenPlayers = new Semaphore(2);
        numPlayers = 0;
        protect = new Semaphore(1);
        canPlay = new Semaphore(0);
        finishedPlaying = new Semaphore(0);

    }

    public static class GreenPlayer extends Thread {


        public void execute() throws InterruptedException {
           // System.out.println("Green player ready");

            greenPlayers.acquire();
            System.out.println("Green player enters field");
            protect.acquire();
            numPlayers++;
            boolean controller = false;
            if(numPlayers == 4){
                controller = true;
                canPlay.release(4);
            }
            protect.release();

            canPlay.acquire();
            System.out.println("Match started");
            Thread.sleep(200);
            System.out.println("Green player finished playing");
            finishedPlaying.release();
            if(controller) {
                finishedPlaying.acquire(4);
                System.out.println("Match finished");
                numPlayers = 0;
                greenPlayers.release(2);
                redPlayers.release(2);
            }
        }

        @Override
        public void run() {
            try {
                execute();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static class RedPlayer extends Thread {

        @Override
        public void run() {
            try {
                execute();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        public void execute() throws InterruptedException {
         //   System.out.println("Red player ready");

            redPlayers.acquire();
            System.out.println("Red player enters field");
            protect.acquire();
            numPlayers++;
            boolean controller = false;
            if(numPlayers == 4){
                controller = true;
                canPlay.release(4);
            }
            protect.release();

            canPlay.acquire();
            System.out.println("Match started");
            Thread.sleep(200);
            System.out.println("Red player finished playing");
            finishedPlaying.release();

            if(controller) {
                finishedPlaying.acquire(4);
                System.out.println("Match finished");
                numPlayers = 0;
                greenPlayers.release(2);
                redPlayers.release(2);
            }
        }

    }


    public static void main(String[] args) throws InterruptedException {
        HashSet<Thread> threads = new HashSet<Thread>();
        for (int i = 0; i < 30; i++) {
            RedPlayer red = new RedPlayer();
            threads.add(red);
            GreenPlayer green = new GreenPlayer();
            threads.add(green);
        }
        init();
        // start 30 red and 30 green players in background
        for(Thread t:threads){
            t.start();
        }
        // after all of them are started, wait each of them to finish for 1_000 ms
        for(Thread t:threads){
            t.join();
        }
        // after the waiting for each of the players is done, check the one that are not finished and terminate them
        System.err.println("Uspeshna sinhronizacija");
    }

}