PA2 Java

gistfile1.txt

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Created with IntelliJ IDEA.
 * User: vvlad
 * Date: 4/2/13
 * Time: 3:21 PM
 * To change this template use File | Settings | File Templates.
 */

class Chopstick
{
    ReentrantLock lock = new ReentrantLock();
    public Chopstick()
    {

    }
    boolean take()
    {
        if (!this.lock.isLocked()) {
            this.lock.lock();
            return true;
        }
        return false;
    }
    void put()
    {
        this.lock.unlock();
    }
}

class Philosopher implements Runnable
{
    private final int maxPause = 100;
    private int maxEatTime = 5;
    int number;
    Chopstick left, right;
    int eattime = 1;

    public Philosopher(int i,Chopstick left, Chopstick right)
    {
        this.number = ++i;
        this.left = left;
        this.right = right;
    }



    public void eat()
    {
        boolean hasleft = _takeLeft();
        boolean hasright = _takeRight();
        if (hasright && hasleft)
        {
            System.out.println("Philosopher " + number + " eats: "+eattime);
        }
        if (hasright)
            _putRight();
        if (hasleft)
            _putLeft();
        if (hasright && hasleft)
        {
            eattime++;
        }
    }
    private boolean _takeLeft()
    {
        boolean hasleft = false;
        if (left.take())
        {
            System.out.println("Philosopher "+number+" picks up left chopstick: "+eattime);
            hasleft = true;
            pause();
        }
        return hasleft;
    }

    private boolean _takeRight()
    {
        boolean hasright = false;
        if (right.take())
        {
            System.out.println("Philosopher "+number+" picks up right chopstick: "+eattime);
            hasright = true;
            pause();
        } else {
            System.out.println("Philosopher "+number+" failed to pick right chopstick - it is busy: "+eattime);
        }
        return hasright;
    }

    private void _putLeft() {
        System.out.println("Philosopher "+number+" puts left chopstick: "+eattime);
        left.put();
        pause();
    }

    private void _putRight() {
        System.out.println("Philosopher "+number+" puts right chopstick: "+eattime );
        right.put();
        pause();
    }

    /**
     * Make random pause - to decrease contention cases and reduce number of retries
     */
    public void pause() {
        try {
            int pause = (int) (Math.random() * maxPause);
            Thread.sleep(pause);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }



    @Override
    public void run() {
        while (eattime<= maxEatTime)
            eat();
    }
}

public class DiningPhilosophers {
    private final int size = 3;
    List<Chopstick> chopsticks = new ArrayList<Chopstick>();
    List<Thread> philosophers = new ArrayList<Thread>();

    void run()
    {
        for (int i=0;i< size;i++) {
            chopsticks.add(new Chopstick());
        }
        for (int i=0;i< size;i++)
        {
            int left = i;
            int right = i<size-1 ? i+1 : 0;
            Thread t = new Thread(new Philosopher(i,chopsticks.get(left),chopsticks.get(right)));
            t.start();
            philosophers.add(t);
        }
        for (Thread t : philosophers) {
            try {
                t.join(1000000);
            } catch (InterruptedException e) {
                e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
            }
        }
    }
    public static void main(String[] args){
        System.out.println("Dinner is starting!");
        DiningPhilosophers dt = new DiningPhilosophers();
        dt.run();
        System.out.println("Dinner is over!");

    }
}