"The five philosophers" by petrovg

Tue, 20 Nov 2007 01:54:00 PST

Here’s my little implementation of the five philosophers problem.

The chopstick:



package philosophers;

public class Chopstick {

    private int number;

    public Chopstick(int number) {
        this.number = number;
    }
    public int getNumber() {
        return number;
    }
}

The philosopher:



package philosophers;

public class Philosopher implements Runnable {

    private int number;

    private Chopstick leftChopstick;

    private Chopstick rightChopstick;

    public Philosopher(int number, Chopstick leftChopstick,
            Chopstick rightChopstick) {
        this.number = number;
        this.leftChopstick = leftChopstick;
        this.rightChopstick = rightChopstick;
    }

    private void eat(int time) {
        synchronized (leftChopstick) {
            System.out.println("Philosopher " + this.number
                    + " took chopstick " + leftChopstick.getNumber()
                    + " from the left.");
            synchronized (rightChopstick) {
                System.out.println("Philosopher " + this.number
                        + " took chopstick " + rightChopstick.getNumber()
                        + " from the right.");
                try {
                    System.out.println("Philosopher " + this.number
                            + " is eating...");
                    Thread.sleep(time);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }

    private void think(int time) {
        try {
            System.out.println("Philosopher " + this.number + " is thinking...");
            Thread.sleep(time);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }

    public void run() {
        while (true) {
            think(1);
            eat(1);
        }
    }

}

And, bringing them all together, the Table:



package philosophers;

public class Table {

    /**
     * Chopstick 0 is on the left of phylosopher 0
     */
    private Chopstick[] chopsticks;

    private Philosopher[] philosophers;

    public void build(int numberOfSeats) {
        for (int i = 0; i < numberOfSeats; i++) {
            chopsticks[i] = new Chopstick(i);
        }
        for (int i = 0; i < numberOfSeats; i++) {
            philosophers[i] = new Philosopher(i, chopsticks[i],
                    chopsticks[i < numberOfSeats - 1 ? i + 1 : 0]);
        }
    }

    public Table(int numberOfSeats) {
        chopsticks = new Chopstick[numberOfSeats];
        philosophers = new Philosopher[numberOfSeats];
        build(numberOfSeats);
    }

    public void start() {
        System.out.println("Chopstick 0 is on the left of philosopher 0");
        for (Philosopher philosopher : philosophers) {
            new Thread(philosopher).start();
        }
    }

    public static void main (String[] args) {
        new Table(5).start();
    }
}

Deadlocks pretty quickly with the numbers as they are here.

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"The five philosophers" by petrovg