OS - Macau Card Tournament Problem

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


public class MacauCardTournament {

    static Semaphore redEnter = new Semaphore(2);
    static Semaphore greenEnter = new Semaphore(2);
    static int players = 0;
    static Semaphore lock = new Semaphore(1);
    static Semaphore canPlay = new Semaphore(0);
    static Semaphore nextRound = new Semaphore(0);
    static Semaphore nextStart = new Semaphore(0);

    static class GreenPlayer extends Thread {


        public void execute() throws InterruptedException {
            System.out.println("Green player ready");
            Thread.sleep(50);
            greenEnter.acquire();
            lock.acquire();
            System.out.println("Green player here");
            players++;
            if(players==4) {
                canPlay.release(4);
            }
            lock.release();
            canPlay.acquire();

            for(int num=1;num<=3;num++) {
                // TODO: the following code should be executed 3 times
                lock.acquire();
                if(players==4) {
                    nextStart.release(4);
                }
                lock.release();

                nextStart.acquire();
                System.out.println("Green Game "+ num +" started");
                Thread.sleep(200);
                System.out.println("Green player finished game "+ num);

                lock.acquire();
                --players;
                if(players==0) {
                    if(num==3) {
                        // TODO: only one player calls the next line per match
                        nextRound.drainPermits();
                        //nextRound.acquire(nextRound.availablePermits());
                        System.out.println("Match finished");
                        greenEnter.release(2);
                        redEnter.release(2);

                    } else {
                        //TODO: only one player calls the next line per game
                        System.out.println("Game "+ num +" finished");
                        players=4;
                        nextRound.release(4);
                    }
                }
                lock.release();

                nextRound.acquire();
            }

        }


        public void run() {
            try {
                execute();
            }catch(Exception e) {
                e.printStackTrace();
            }
        }

    }

    static class RedPlayer extends Thread{



        public void execute() throws InterruptedException {
            System.out.println("Red player ready");
            Thread.sleep(50);
            redEnter.acquire();
            lock.acquire();
            System.out.println("Red player here");
            System.out.println("Players:" + players);
            players++;
            if(players==4) {
                canPlay.release(4);
            }
            lock.release();
            canPlay.acquire();

            for(int num=1;num<=3;num++) {
                lock.acquire();
                if(players==4) {
                    nextStart.release(4);
                }
                lock.release();
                // TODO: the following code should be executed 3 times
                System.out.println("Red Game "+ num +" started");
                Thread.sleep(200);
                System.out.println("Red player finished game "+ num);

                lock.acquire();
                --players;
                if(players==0) {
                    if(num==3) {
                        // TODO: only one player calls the next line per match
                        nextRound.drainPermits();
                        //nextRound.acquire(nextRound.availablePermits());
                        System.out.println("Match finished");
                        redEnter.release(2);
                        greenEnter.release(2);

                    } else {
                        //TODO: only one player calls the next line per game
                        System.out.println("Game "+ num +" finished");
                        players=4;
                        nextRound.release(4);
                    }
                }
                lock.release();
                nextRound.acquire();
            }


        }
        public void run() {
            try {
                execute();
            }catch(Exception e) {
                e.printStackTrace();
            }
        }
    }


    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);
        }
        //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(100);
        }
        //after the waiting for each of the players is done, check the one that are not finished and terminate them
        for(Thread t : threads) {
            if(t.isAlive()) {
                t.interrupt();
                 System.err.println("Possible deadlock");
            }
        }


    }

}