//: concurrency/DeadlockingDiningPhilosophers.java
package concurrency;
import java.util.concurrent.*;
public class DeadlockingDiningPhilosophers {
public static void main(String[] args) throws Exception {
int ponder = 5;
if(args.length > 0)
ponder = Integer.parseInt(args[0]);
int size = 5;
if(args.length > 1)
size = Integer.parseInt(args[1]);
ExecutorService exec = Executors.newCachedThreadPool();
Chopstick[] sticks = new Chopstick[size];
for(int i = 0; i < size; i++)
sticks[i] = new Chopstick();
for(int i = 0; i < size; i++)
exec.execute(new Philosopher(
sticks[i], sticks[(i+1) % size], i, ponder));
if(args.length == 3 && args[2].equals("timeout"))
TimeUnit.SECONDS.sleep(5);
else {
System.out.println("Press 'Enter' to quit");
System.in.read();
}
exec.shutdownNow();
}
}
//: concurrency/Philosopher.java
package concurrency;
import java.util.concurrent.*;
import java.util.*;
import static util.Print.*;
public class Philosopher implements Runnable {
private Chopstick left;
private Chopstick right;
private final int id;
private final int ponderFactor;
private Random rand = new Random(47);
private void pause() throws InterruptedException {
if(ponderFactor == 0) return;
TimeUnit.MILLISECONDS.sleep(
rand.nextInt(ponderFactor * 250));
}
public Philosopher(Chopstick left, Chopstick right,
int ident, int ponder) {
this.left = left;
this.right = right;
id = ident;
ponderFactor = ponder;
}
public void run() {
try {
while(!Thread.interrupted()) {
print(this + " " + "thinking");
pause();
print(this + " " + "grabbing right");
right.take();
print(this + " " + "grabbing left");
left.take();
print(this + " " + "eating");
pause();
right.drop();
left.drop();
}
} catch(InterruptedException e) {
print(this + " " + "exiting via interrupt");
}
}
public String toString() { return "Philosopher " + id; }
} ///:~
//: concurrency/Chopstick.java
package concurrency;
public class Chopstick {
private boolean taken = false;
public synchronized
void take() throws InterruptedException {
while(taken)
wait();
taken = true;
}
public synchronized void drop() {
taken = false;
notifyAll();
}
} ///:~