How solve consumer/producer task using semaphores
- by user1074896
I have SimpleProducerConsumer class that illustrate consumer/producer problem (I am not sure that it's correct).
public class SimpleProducerConsumer {
private Stack<Object> stack = new Stack<Object>();
private static final int STACK_MAX_SIZE = 10;
public static void main(String[] args) {
SimpleProducerConsumer pc = new SimpleProducerConsumer();
new Thread(pc.new Producer(), "p1").start();
new Thread(pc.new Producer(), "p2").start();
new Thread(pc.new Consumer(), "c1").start();
new Thread(pc.new Consumer(), "c2").start();
new Thread(pc.new Consumer(), "c3").start();
}
public synchronized void push(Object d) {
while (stack.size() >= STACK_MAX_SIZE)
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
stack.push(new Object());
System.out.println("push " + Thread.currentThread().getName() + " " + stack.size());
notify();
}
public synchronized Object pop() {
while (stack.size() == 0)
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
stack.pop();
System.out.println("pop " + Thread.currentThread().getName() + " " + stack.size());
notify();
return null;
}
class Consumer implements Runnable {
@Override
public void run() {
while (true) {
pop();
}
}
}
class Producer implements Runnable {
@Override
public void run() {
while (true) {
push(new Object());
}
}
}
}
I found simple realization of semaphore(here:http://docs.oracle.com/javase/tutorial/essential/concurrency/guardmeth.html I know that there is concurrency package)
How I need to change code to exchange java objects monitors to my custom semaphore.
(To illustrate C/P problem using semaphores)
Semaphore:
class Semaphore {
private int counter;
public Semaphore() {
this(0);
}
public Semaphore(int i) {
if (i < 0)
throw new IllegalArgumentException(i + " < 0");
counter = i;
}
public synchronized void release() {
if (counter == 0) {
notify();
}
counter++;
}
public synchronized void acquire() throws InterruptedException {
while (counter == 0) {
wait();
}
counter--;
}
}
