/*******Q4 Source Code for CS 580*********/
/***************  Zhen Chen **************/
/*****************************************/

class Range implements Runnable {
    int low, high;
    IteratorHelper<int> ih = new IteratorHelper<int>(this);

    public Range (int low, int high) {
      this.low = low;
      this.high = high;
    }

    public boolean hasNext() {
      return ih.done();
    }

    public int next() {
      if (this.hasNext())
        return ih.get();
    }

    run () {
      for (int i = low; i< high; i++) {
        ih.yield(i);
      }
      ih.finish();
    }
}


class IteratorHelper<T> {
    private Boolean lock = false;
    private Boolean NoElement = false;
    private Thread t;
    private <T> v, v1;

    public IteratorHelper (Runnable r) {
      t = new Thread(r); //creat a new thread for runnable object r
      this.start();
    }

    public void start() {
      t.start(); //start the iterator in the new thread
    }

    public synchronized void yield(<T> v) { 
      while (lock) {
        wait();      //wait until the element is retrieved by get()
      }
      this.v = v; 
      lock = true;  // lock the yield until the value is fetched by get()
      notify(); //tell the get() the element is available to retrieve
    }
    
    public synchronized <T> get() { 
      while (!lock) {
        wait();     //wait until the element is sent by yield();
      }
      this.v1 = this.v; //Maybe no needed, just to be safe
      lock = false;   // release the lock for yield()
      notify();//tell the yield the element is sucessfully retrieved
      return this.v1;
    }

    public synchronized Boolean done() {
      if (!NoElement)
        return true;
      else {
        t.join(); // Job done! The end of the thread
        return false;
      }
    }
    
    public synchronized void finish() {
      NoElement = true; //No more value to yield
    }
}