Deck.java

package common.handeval.klaatu;

import java.util.Random;

public final class Deck {
	public static final char[] RANKS = new char[] { '2', '3', '4', '5', '6', '7', '8', '9', 'T', 'J', 'Q', 'K', 'A' };
	public static final char[] SUITS = new char[] { 'H', 'S', 'C', 'D' };

	private static long seed = new Random().nextLong();
	private static int[] deck;
	private static int[] ret = new int[7];

	static {
		deck = new int[52];
		for (int i = 0; i < 52; i++) {
			deck[i] = i;
		}
	}

	public static final int[] getCards() {
		randomHand(7);
		System.arraycopy(deck, 0, ret, 0, 7);
		return ret;
	}

	public static final void randomHand(int cards) {
		for (int i = 0; i < cards; i++) {
			int idx = (int) (random() * (double) (52 - i)) + i;
			int swap = deck[i];
			deck[i] = deck[idx];
			deck[idx] = swap;
		}
	}

	/**
	 * XorShift random number generation
	 * it is faster and statically more random than java.util.Random
	 */
	private static final double random() {
		seed ^= (seed << 21);
		seed ^= (seed >>> 35);
		seed ^= (seed << 4);
		return (double) Math.abs(seed) / Long.MAX_VALUE;
	}

	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append("[");
		String delim = "";
		for (int i = 0; i < 7; i++) {
			sb.append(delim).append(RANKS[deck[i] >> 2]).append(SUITS[deck[i] & 3]);
			delim = " ";
		}
		return sb.append("]").toString();
	}

}