Philosopher.java Source code

Introduction

Here is the source code for Philosopher.java

Source

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class Philosopher implements Runnable {
    State hlp;
    Chopstick l, r;
    int id;

    public Philosopher(int id, Chopstick l, Chopstick r, State i) {
        this.hlp = i;
        this.l = l;
        this.r = r;
        this.id = id;
    }

    private void eat() {
        try {
            Thread.sleep(2000);
            System.out.println(id + " Eat");
        } catch (Exception e) {
        }
    }

    private void think() {
        try {
            Thread.sleep(2000);
            System.out.println(id + " think");
        } catch (Exception e) {
        }
    }

    public void run() {
        while (true) {
            hlp.grabChopsticks(id, l, r);
            eat();
            hlp.releaseChopsticks(id, l, r);
            think();
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Chopstick[] s = new Chopstick[5];
        Philosopher[] f = new Philosopher[5];
        State hlp = new State();
        for (int i = 0; i < 5; i++) {
            s[i] = new Chopstick();
        }
        for (int i = 0; i < 5; i++) {
            f[i] = new Philosopher(i, s[i], s[(i + 4) % 5], hlp);
            new Thread(f[i]).start();
        }
    }
}

class Chopstick {
    private boolean availability;

    public Chopstick() {
        availability = true;
    }

    public boolean getAvailability() {
        return availability;
    }

    public void setAvailability(boolean flag) {
        availability = flag;
    }
}

class State {
    Lock mutex = new ReentrantLock();
    Condition[] cond = new Condition[5];
    String[] state = new String[5];
    int[] id = new int[5];

    void outputState(int id) {
        StringBuffer line = new StringBuffer();
        for (int i = 0; i < 5; i++) {
            line.append(state[i] + " ");
        }
        System.out.println(line + "(" + (id + 1) + ")");
    }

    public State() {
        for (int i = 0; i < 5; i++) {
            id[i] = i;
            state[i] = "O";
            cond[i] = mutex.newCondition();
        }
    }

    public void setState(int id, String s) {
        state[id] = s;
    }

    public void grabChopsticks(int id, Chopstick l, Chopstick r) {
        mutex.lock();
        try {
            setState(id, "o");
            while (!l.getAvailability() || !r.getAvailability()) {
                cond[id].await();
            }
            l.setAvailability(false);
            r.setAvailability(false);
            setState(id, "X");
            outputState(id);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            mutex.unlock();
        }
    }

    public void releaseChopsticks(int id, Chopstick l, Chopstick r) {
        mutex.lock();
        setState(id, "O");
        l.setAvailability(true);
        r.setAvailability(true);
        cond[(id + 1) % 5].signalAll();
        cond[(id + 4) % 5].signalAll();
        outputState(id);
        mutex.unlock();
    }
}