Producer consumer in Java 2
/*
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
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*
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*
* Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
* pioneering role in inventing and promulgating (and standardizing) the Java
* language and environment is gratefully acknowledged.
*
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/
import java.util.*;
import java.io.*;
/** Producer-consumer in Java, Take II.
*/
public class ProdCons2 {
/** Throughout the code, this is the object we synchronize on so this
* is also the object we wait() and notifyAll() on.
*/
protected LinkedList list = new LinkedList();
protected int MAX = 10;
protected boolean done = false; // Also protected by lock on list.
/** Inner class representing the Producer side */
class Producer extends Thread {
public void run() {
while (true) {
Object justProduced = getRequestFromNetwork();
// Get request from the network - outside the synch section.
// We're simulating this actually reading from a client, and it
// might have to wait for hours if the client is having coffee.
synchronized(list) {
while (list.size() == MAX) // queue "full"
try {
System.out.println("Producer WAITING");
list.wait(); // Limit the size
} catch (InterruptedException ex) {
System.out.println("Producer INTERRUPTED");
}
list.addFirst(justProduced);
list.notifyAll(); // must own the lock
System.out.println("Produced 1; List size now " + list.size());
if (done)
break;
// yield(); // Useful for green threads & demo programs.
}
}
}
Object getRequestFromNetwork() { // Simulation of reading from client
// try {
// Thread.sleep(10); // simulate time passing during read
// } catch (InterruptedException ex) {
// System.out.println("Producer Read INTERRUPTED");
// }
return(new Object());
}
}
/** Inner class representing the Consumer side */
class Consumer extends Thread {
public void run() {
while (true) {
Object obj = null;
synchronized(list) {
while (list.size() == 0) {
try {
System.out.println("CONSUMER WAITING");
list.wait(); // must own the lock
} catch (InterruptedException ex) {
System.out.println("CONSUMER INTERRUPTED");
}
}
obj = list.removeLast();
list.notifyAll();
int len = list.size();
System.out.println("List size now " + len);
if (done)
break;
}
process(obj); // Outside synch section (could take time)
//yield(); DITTO
}
}
void process(Object obj) {
// Thread.sleep(xxx) // Simulate time passing
System.out.println("Consuming object " + obj);
}
}
ProdCons2(int nP, int nC) {
for (int i=0; i<nP; i++)
new Producer().start();
for (int i=0; i<nC; i++)
new Consumer().start();
}
public static void main(String[] args)
throws IOException, InterruptedException {
// Start producers and consumers
int numProducers = 4;
int numConsumers = 3;
ProdCons2 pc = new ProdCons2(numProducers, numConsumers);
// Let it run for, say, 10 seconds
Thread.sleep(10*1000);
// End of simulation - shut down gracefully
synchronized(pc.list) {
pc.done = true;
pc.list.notifyAll();
}
}
}
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