MontyHall.java

public class MontyHall {
	public static void main(String... args) {
		boolean[] doors = new boolean[3];

		int wins = 0;
		int losses = 0;

		int tries = 10000000;
		for (int i = 1; i <= tries; i++) {
			// fill doors
			for (int j = 0; j < doors.length; j++) {
				doors[j] = false;
			}
			int winIndex = (int) (Math.random() * doors.length);
			doors[winIndex] = true;

			// pick random door
			int pickIndex = (int) (Math.random() * doors.length);

			// find remaining losing door
			int loseIndex = -1;
			for (int j = 0; j < doors.length; j++) {
				if ((j != pickIndex) && !doors[j]) {
					loseIndex = j;
					break;
				}
			}

			// change pick
			for (int j = 0; j < doors.length; j++) {
				if ((j != pickIndex) && (j != loseIndex)) {
					pickIndex = j;
					break;
				}
			}

			if (doors[pickIndex]) {
				wins++;
			} else {
				losses++;
			}
		}

		float winPercent = (float) wins / (float) tries;
		System.err.printf("wins: %.2f%%", winPercent * 100f).println();
	}
}