// Monitor.java

public class Monitor {
        boolean  hecho = false;

        /**
         * Waits until done is set to true.
         */
        public void espera() {
            synchronized (this) {
                while (! hecho) {
                    try {
                        this.wait();
                    } catch (InterruptedException ie) {}
                }
            }
        }
        
        /**
         * Sets done to true.
         */
        public void finalizado() {
            synchronized (this) {
                hecho = true;
                this.notify();
            }
        }
    }