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

    private Object[] buffer;
    private int nextToRemove;
    private int numElements;

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

    /**
     * Put item 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 {
        System.err.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();
        System.err.println("ending put with numElements = " + numElements);
    }

    /**
     * Get item from buffer.
     * Waits if buffer is empty; wakes up all waiting threads on exit.
     * Allows exceptions thrown by wait() to bubble up.
     * @return item
     */
    public synchronized Object get() throws InterruptedException {
        System.err.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();
        System.err.println("ending get with numElements = " + numElements);
        return o;
    }

    /**
     * Check with buffer is empty.
     */
    public synchronized boolean isEmpty() {
        return (numElements == 0);
    }
}