Application: The Consumer/Producer Problem

1. The Consumer/Producer problem was addressed in class and is described in module 5. A solution to this problem is presented on the picture below (in pseudo-language). This particular solution uses 3 semaphores: e, s, and n. Semaphore e is used to protect access to the critical sections. Semaphore e is used to ensure that the producer will not try and produce to a full buffer. Semaphore n is used to ensure that the consumer will not try and consume from an empty buffer.

Solve the Consumer/Producer problem using semaphores. A skeleton program is provided to you: The class Consumer.java represents the consumer, and the class Producer.java represents the producer. You need not modify Consumer.java or Producer.java, however, you should declare and initialize 3 semaphores in BoundedBuffer.java. Those semaphore should be used in the removeItem(..) and addItem(...) methods of BoundedBuffer.

import java.util.Random;

public class Consumer extends Thread {

private BoundedBuffer buffer;

private final Random random = new Random(System.currentTimeMillis());

public Consumer(BoundedBuffer b) {

buffer = b;

}

public void run() {

int item;

while (true) {

try {

//random number from 0 to 9.9999....

float sleepDuration = random.nextInt(10);

Thread.sleep((int) (sleepDuration * 100));

} catch(InterruptedException e){

System.out.println(this.getName() + " got interrupted!");

}

// consume an item from the buffer

System.out.println("Consumer wants to consume.");

item = buffer.removeItem();

}

}

}

import java.util.Random;

public class Producer extends Thread {

private BoundedBuffer buffer;

private final Random random = new Random(System.currentTimeMillis());

public Producer(BoundedBuffer b) {

buffer = b;

}

public void run() {

int item;

while (true) {

try {

//random number from 0 to 9.9999....

float sleepDuration = random.nextInt(10);

Thread.sleep((int) (sleepDuration * 10));

} catch(InterruptedException e){

System.out.println(this.getName() + " got interrupted!");

}

// add an item into the buffer

System.out.println("Producer wants to produce.");

buffer.addItem(random.nextInt(10));

}

}

}

public class BoundedBuffer {

private static final int BUFFER_SIZE = 10;

private int[] buffer;

private int in, out;

private int n;

public BoundedBuffer(){

out = 0; //index of the item to be consumed next

in = 0; //index of the item to be produced next

n = 0; //number of items in the buffer

buffer = new int [BUFFER_SIZE];

}

public void addItem(int item){

//critical section below

n++;

buffer[in] = item;

in = (in + 1) % BUFFER_SIZE;

System.out.println("Producer entered " + item + ". Buffer Size = " + n);

//critical section above

}

public int removeItem(){

//critical section below

n--;

int item = buffer[out];

out = (out + 1) % BUFFER_SIZE;

System.out.println("Consumer consumed " + item + ". Buffer Size = " + n);

//critical section above

return item;

}

public static void main(String[] args){

BoundedBuffer buffer = new BoundedBuffer();

Producer pThread = new Producer(buffer);

Consumer cThread = new Consumer(buffer);

pThread.start();

cThread.start();

}

}

Please provide your code (modified BoundedBuffer) and a sample output