Math problem from 21 movie - https://www.youtube.com/watch?v=8DMnAAvakh0

3 doors problem simulation.java

int count = 100000000;
int hits = 0;

Random random = new Random();
for (int i = 0; i < count; i++) {
  final List<Integer> doors = new ArrayList<>();
  doors.add(0);
  doors.add(1);
  doors.add(2);

  Integer answer = random.nextInt(3);
  Integer choosen = random.nextInt(3);

  final List<Integer> notAnswerAndNotChoosen = new ArrayList<>(doors);
  notAnswerAndNotChoosen.remove(answer);
  notAnswerAndNotChoosen.remove(choosen);

  Integer notAnswer = notAnswerAndNotChoosen.get(random.nextInt(notAnswerAndNotChoosen.size()));

  doors.remove(notAnswer);
  doors.remove(choosen);

  if (random.nextBoolean()) {
    choosen = doors.get(0);
  }

  if (choosen == answer) {
    hits++;
  }
}

log.debug("Probability: {}", (double) hits / count);

Turn off line 23. for original solution.