ビット演算を駆使したFizzBuzz

FizzBuzz.java

package jp.hishidama.joke;

public class FizzBuzz {

	public static void main(String[] args) {
		for (String s : args) {
			System.out.println(new FizzBuzz(s));
		}
	}

	public static final String FIZZ = "Fizz";
	public static final String BUZZ = "Buzz";

	private String s;

	public FizzBuzz(String s) {
		this.s = s;
	}

	@Override
	public String toString() {
		int b = fizz(s) | buzz(s);
		int r = b ^ 3;
		int n = (r & 1) * FIZZ.length() + ((r >> 1) & r) * BUZZ.length();
		int l = ((r >> 1) & r) * s.length() + (b & 1) * FIZZ.length()
				+ (b >> 1) * BUZZ.length();
		return (FIZZ + BUZZ + s).substring(n, n + l);
	}

	int fizz(String s) {
		// Java7だとswitchでStringが指定できるので、このif文も削れる
		if (s.length() == 1) {
			switch (s.charAt(0)) {
			case '0':
			case '3':
			case '6':
			case '9':
				return 1;
			default:
				return 0;
			}
		}

		int n = 0;
		for (char c : s.toCharArray()) {
			n += c - '0';
		}
		return fizz(String.valueOf(n));
	}

	int buzz(String s) {
		switch (s.charAt(s.length() - 1)) {
		case '0':
		case '5':
			return 2;
		default:
			return 0;
		}
	}
}