Please help to fix below code by making it deadlock-free.

import java.util.Random;

public class DiningPhil {

private static int N = 5;

public static void main (String[] args) throws Exception {

Philosopher[] phils = new Philosopher[N];

Fork[] forks = new Fork[N];

for (int i = 0; i < N; i++) {

forks[i] = new Fork(i);

}

for (int i = 0; i < N; i++) {

phils[i] = new Philosopher (i, forks[i], forks[(i+N-1)%N]);

phils[i].start();

}

}

}

class Philosopher extends Thread {

private final int index;

private final Fork left;

private final Fork right;

public Philosopher (int index, Fork left, Fork right) {

this.index = index;

this.left = left;

this.right = right;

}

public void run() {

Random randomGenerator = new Random();

try {

while (true) {

Thread.sleep(randomGenerator.nextInt(100)); //not sleeping but thinking

System.out.println("Phil " + index + " finishes thinking.");

left.pickup();

System.out.println("Phil " + index + " picks up left fork.");

right.pickup();

System.out.println("Phil " + index + " picks up right fork.");

Thread.sleep(randomGenerator.nextInt(100)); //eating

System.out.println("Phil " + index + " finishes eating.");

left.putdown();

System.out.println("Phil " + index + " puts down left fork.");

right.putdown();

System.out.println("Phil " + index + " puts down right fork.");

}

} catch (InterruptedException e) {

System.out.println("Don't disturb me while I am sleeping, well, thinking.");

}

}

}

class Fork {

private final int index;

private boolean isAvailable = true;

public Fork (int index) {

this.index = index;

}

public synchronized void pickup () throws InterruptedException {

while (!isAvailable) {

wait();

}

isAvailable = false;

notifyAll();

}

public synchronized void putdown() throws InterruptedException {

while (isAvailable) {

wait();

}

isAvailable = true;

notifyAll();

}

public String toString () {

if (isAvailable) {

return "Fork " + index + " is available.";

}

else {

return "Fork " + index + " is NOT available.";

}

}

}