import java.util.*;
import java.util.concurrent.Semaphore;
import java.lang.Object;
import java.nio.Buffer;

public class BoundedBuffer<E> implements Buffer<E>
{
    private static final int BUFFER_SIZE=5;
    private E[] buffer;
    private int in, out;
    private Semaphore mutex;
    private Semaphore empty;
    private Semaphore full;

    public BoundedBuffer()
    {
        //buffer is initially empty
        in=0;
        out=0;
        mutex= new Semaphore(1);
        empty= new Semaphore(BUFFER_SIZE);
        full=new Semaphore(0);

        buffer=(E[]) new Object[BUFFER_SIZE];

    }

    public void insert(E item)
    {
        empty.acquire();
        mutex.acquire();

        //add item
        buffer[in]=item;
        in=(in+1)%BUFFER_SIZE;

        mutex.release();
        full.release();
    }

    public E remove()
    {
        E item;

        full.acquire();
        mutex.acquire();

        //remove item
        item=buffer[out];
        out=(out+1)%BUFFER_SIZE;

        mutex.release();
        empty.release();

        return item;
    }
}