Monitor

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package assignment3;

/**
 *
 * @author Zizo
 */
public class Monitor {

    private enum State {

        THINKING, HUNGRY, EATING
    };
    private State[] state = new State[5];

    public Monitor() { //initial state
        for (int i = 0; i < 5; i++) {
            state[i] = State.THINKING;
        }
    }

    public synchronized void pickUp(int id) throws InterruptedException {
        state[id] = State.HUNGRY;
        System.out.println("Philosopher " + id + " is hungry.\n");
        System.out.flush();
        while (someNeighborIsEating(id)) {
            wait();
        }
        state[id] = State.EATING;
        System.out.println("Philosopher " + id + " is eating.\n");
        System.out.flush();
    }

    public synchronized void putDown(int id) {
        state[id] = State.THINKING;
        notifyAll();
    }

    private boolean someNeighborIsEating(int id) {
        if (state[(id + 1) % 5] == State.EATING || state[(id+4) % 5] == State.EATING) {
            return true;
        }
        return false;
    }
}