H2O Machine

import java.util.Arrays;
import java.util.concurrent.Semaphore;

class H2OMachine {

    String[] molecule;
    int count;

    public H2OMachine() {
        molecule = new String[3];
        count = 0;
    }

    static Semaphore hydrogen = new Semaphore(1);
    static Semaphore oxygen = new Semaphore(1);
    static Semaphore hHere = new Semaphore(0);
    static Semaphore countLock = new Semaphore(1);

    public void hydrogen() throws InterruptedException {
        // TODO: 3/29/20 synchronized logic here
        hydrogen.acquire();
        countLock.acquire();
        molecule[count++]="H";
        if(count==3){
            System.out.println("Hydrogen atom 2 arrived");
            System.out.println(String.join("-", molecule));
            count=0;
            countLock.release();
            hydrogen.release();
            oxygen.release();
            return;
        }
        System.out.println("Hydrogen atom 1 arrived");
        hHere.release();
        countLock.release();
    }

    public void oxygen() throws InterruptedException {
        // TODO: 3/29/20 synchronized logic here
        oxygen.acquire();
        hHere.acquire();
        countLock.acquire();
        System.out.println("Oxygen arrived");
        molecule[count++]="O";
        countLock.release();
        hydrogen.release();
    }
}

class H2OThread extends Thread {

    H2OMachine molecule;
    String atom;

    public H2OThread(H2OMachine molecule, String atom) {
        this.molecule = molecule;
        this.atom = atom;
    }

    public void run() {
        if ("H".equals(atom)) {
            try {
                molecule.hydrogen();
            } catch (Exception e) {
            }
        } else if ("O".equals(atom)) {
            try {
                molecule.oxygen();
            } catch (Exception e) {
            }
        }
    }
}

public class Main {
    public static void main(String[] args) throws InterruptedException {

        // TODO: 3/29/20 Simulate with multiple scenarios
        H2OMachine molecule = new H2OMachine();
        int n = 120;
        H2OThread[] threads = new H2OThread[n];
        for (int i = 0; i < n; i++) {
            if (i%3==0) {
                threads[i] = new H2OThread(molecule, "O");
            } else threads[i] = new H2OThread(molecule, "H");
        }
        Arrays.stream(threads).forEach(Thread::start);
    }
}