DiningPhilosophersProblem.java

import java.util.concurrent.Semaphore;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.Random;

public class DiningPhilosophers {

    private static final Random random = new Random();
    private final Semaphore diningSemaphore = new Semaphore(NUM_PHILOSOPHERS - 1);
    public static final int NUM_PHILOSOPHERS = 5;
    private final Lock[] chopsticks = new Lock[NUM_PHILOSOPHERS];
    
    private enum Action {
        THINKING("Thinking"),
        PICKED_LEFT_CHOPSTICK("Picked up left chopstick"),
        PICKED_RIGHT_CHOPSTICK("Picked up right chopstick"),
        EATING("Eating"),
        PUT_DOWN_LEFT_CHOPSTICK("Put down left chopstick"),
        PUT_DOWN_RIGHT_CHOPSTICK("Put down right chopstick");

        private final String actionString;

        Action(String actionString) {
            this.actionString = actionString;
        }

        @Override
        public String toString() {
            return actionString;
        }
    }

    public DiningPhilosophers() {
        for (int i = 0; i < NUM_PHILOSOPHERS; i++) {
            chopsticks[i] = new ReentrantLock();
        }
    }

    public void dine(int philosopherId) throws InterruptedException {
        Lock leftChopstick = chopsticks[philosopherId];
        Lock rightChopstick = chopsticks[(philosopherId + 1) % NUM_PHILOSOPHERS];

        while (true) {

            diningSemaphore.acquire();

            // Attempt to pick up chopsticks
            if (leftChopstick.tryLock()) {
                try {
                    log(philosopherId, Action.PICKED_LEFT_CHOPSTICK);
                    if (rightChopstick.tryLock()) {
                        try {
                            log(philosopherId, Action.PICKED_RIGHT_CHOPSTICK);
                            // Both chopsticks acquired, eat
                            eat(philosopherId);
                        } finally {
                            rightChopstick.unlock();
                            log(philosopherId, Action.PUT_DOWN_RIGHT_CHOPSTICK);
                        }
                    }
                } finally {
                    // Release the left chopstick
                    leftChopstick.unlock();
                    log(philosopherId, Action.PUT_DOWN_LEFT_CHOPSTICK);
                }

                diningSemaphore.release();
            }

            // Think before retrying
            think(philosopherId);
        }
    }
    
    private void log(int philosopherId, Action action) {
        System.out.println("Philosopher " + philosopherId + ": " + action);
    }

    private void eat(int philosopherId) throws InterruptedException {
        log(philosopherId, Action.EATING);
        // Simulating eating to prevent livelock
        Thread.sleep(random.nextInt(100));
    }

    private void think(int philosopherId) throws InterruptedException {
        log(philosopherId, Action.THINKING);
        // Simulating thinking
        Thread.sleep(random.nextInt(100));
    }
}