// stand alone version of j.n.magee 11/11/96
// by mh 19/03/03
// only text user interface

class Counter {

    int value=0;

    Counter(int init) {
        value = init;
    }

    void increment() {
        int temp = value;   	//read[v]
        Simulate.interrupt();
        value=temp+1;      	    //write[v+1]
    }

    int get () {
        return value;
    }

} // class Counter


class Simulate {
    public static void interrupt() {
        if (Math.random() < 0.5)
           try { Thread.sleep(200);} catch(InterruptedException e){};
            //used instead of Thread.yield() to ensure portability
    }
} // class Simulate


class Turnstile extends Thread {
    
    private Counter people;
    private Semaphore mutex;

    Turnstile (Semaphore sema, Counter c) { 
        mutex=sema;
        people = c; 
    }

    public void run() {
      for (int i=1;i<=GardenTuiSema.MAX;i++){
        mutex.down();				    // get mutual exclusion 
        people.increment();
        mutex.up();					    // release mutual exclusion
      }
    }

} // class Turnstile
    

public class GardenTuiSema {

    final static int MAX = 20;

    public static void main (String[] argv) {

        Counter counter = new Counter(0);
        Semaphore mutex = new Semaphore(1);	

		Turnstile west= new Turnstile(mutex,counter);
    	Turnstile east= new Turnstile(mutex,counter);
    	
    	System.out.println(" -- begin of garden using semaphore -- ");
        
        west.start();
        east.start();

        try {
            west.join();	
            east.join(); 
            System.out.println("total count: " + counter.get());
        } catch (Exception e) {}
        
        System.out.println(" -- end of garden using semaphore -- ");

    } 

} // class GardenTui