// ---- Class for bounded buffer, with synchronization ---------------

public class BoundedBuffer {

    // Instance variables.
    private Object[] buffer;
    private int nextToRemove;
    private int numElements;

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

    // 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 {
	// 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();
    }

    // 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 {
	// 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();
	return o;
    }
}