/*
 * class for bounded buffer, with synchronization 
 */
public class BoundedBuffer {

    private Object[] buffer;
    private int nextToRemove;
    private int numElements;
    private boolean verbose = false;    /* if true, verbose output */

    public BoundedBuffer(int sz) {
	buffer = new Object[sz];
	nextToRemove = 0;
	numElements = 0;
    }

    public BoundedBuffer(int sz, boolean verbose) {
        this(sz);
        this.verbose = verbose;
    }

    /* Method to put "itm" into buffer.
     * Waits if buffer is full; wakes up all waiting threads on exit.
     * Allows exceptions thrown by wait() to bubble up.
     */
    public synchronized void put(Object o) throws InterruptedException {
        if (verbose)
            System.out.println("starting put with numElements = " + 
                    numElements);
        /* wait until not full */
	while (numElements == buffer.length) 
	    wait();
	int next = (nextToRemove + numElements) % buffer.length;
	buffer[next] = o;
	++numElements;
        /* wake up any waiting threads, since some might be waiting
	 * for "buffer not empty". 
         */
	notifyAll();
        if (verbose)
            System.out.println("ending put with numElements = " + numElements);
    }

    /* Method to get item from buffer and return.
     * Waits if buffer is empty; wakes up all waiting threads on exit.
     * Allows exceptions thrown by wait() to bubble up.
     */
    public synchronized Object get() throws InterruptedException {
        if (verbose)
            System.out.println("starting get with numElements = " + 
                    numElements);
	/* wait until not empty */
	while (numElements == 0)
	    wait();
	Object o = buffer[nextToRemove];
	nextToRemove = (nextToRemove + 1) % buffer.length;
	--numElements;
	/* Wake up any waiting threads, since some might be waiting 
	 *   for "buffer not full". */
	notifyAll();
        if (verbose)
            System.out.println("ending get with numElements = " + numElements);
	return o;
    }

    /* Method to check whether buffer is empty. */
    public synchronized boolean isEmpty() {
        return (numElements == 0);
    }
}