Javaじゃんけん3

JankenExample3.java

package example;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Random;
import java.util.function.Function;
import java.util.stream.Collectors;

/**
 * http://blog.goo.ne.jp/hishidama/e/ee5bacfceb7179b942d3392bb83e21a6
 * <p>
 * JDK1.8
 * </p>
 * 
 * @author hishidama
 */
public class JankenExample3 {

	public enum Hand {
		/** グー */
		ROCK("グー", "1") {
			@Override
			public boolean isWinTo(Hand other) {
				return other == SCISSORS;
			}
		},
		/** チョキ */
		SCISSORS("チョキ", "2") {
			@Override
			public boolean isWinTo(Hand other) {
				return other == PAPER;
			}
		},
		/** パー */
		PAPER("パー", "3") {
			@Override
			public boolean isWinTo(Hand other) {
				return other == ROCK;
			}
		};

		private final String label;
		private final String key;

		private Hand(String label, String key) {
			this.label = label;
			this.key = key;
		}

		public String label() {
			return label;
		}

		public String key() {
			return key;
		}

		public abstract boolean isWinTo(Hand other);
	}

	private static final List<Hand> HAND_LIST;
	private static final String HAND_MIN_KEY;
	private static final String HAND_MAX_KEY;
	private static final Map<String, Hand> KEY_HAND_MAP;
	static {
		HAND_LIST = Arrays.asList(Hand.values());
		HAND_MIN_KEY = HAND_LIST.stream().map(Hand::key).min(Comparator.naturalOrder()).get();
		HAND_MAX_KEY = HAND_LIST.stream().map(Hand::key).max(Comparator.naturalOrder()).get();
		KEY_HAND_MAP = HAND_LIST.stream().collect(Collectors.toMap(Hand::key, Function.identity()));
	}

	protected final BufferedReader reader;

	int winCount = 0;
	int loseCount = 0;

	public JankenExample3(BufferedReader reader) {
		this.reader = reader;
	}

	public void loop() throws IOException {
		for (;;) {
			Hand input = getInputHand();
			Hand other = getComputerHand();
			if (!judge(input, other)) {
				continue;
			}

			if (isEnd()) {
				break;
			}
		}
	}

	protected Hand getInputHand() throws IOException {
		for (;;) {
			for (Hand hand : HAND_LIST) {
				System.out.printf("%s %s\n", hand.key(), hand.label());
			}
			System.out.printf("%s〜%sを入力してEnterを押して下さい。→", HAND_MIN_KEY, HAND_MAX_KEY);

			String line = reader.readLine();
			if (line == null) {
				throw new IOException("EOF");
			}
			Optional<Hand> input = parseInput(line);
			if (input.isPresent()) {
				return input.get();
			}

			System.out.println("認識できない文字でした。もう一度入力して下さい。");
		}
	}

	protected Optional<Hand> parseInput(String key) {
		return Optional.ofNullable(KEY_HAND_MAP.get(key));
	}

	private final Random random = new Random();

	protected Hand getComputerHand() {
		return HAND_LIST.get(random.nextInt(HAND_LIST.size()));
	}

	protected boolean judge(Hand input, Hand other) {
		assert input != null;
		assert other != null;

		if (input == other) {
			System.out.printf("あなたは%s、わたしは%sで、あいこでした。\n", input.label(), other.label());
			return false;
		}

		if (input.isWinTo(other)) {
			System.out.printf("あなたは%s、わたしは%sで、あなたの勝ちです。\n", input.label(), other.label());
			winCount++;
		} else {
			System.out.printf("あなたは%s、わたしは%sで、わたしの勝ちです。\n", input.label(), other.label());
			loseCount++;
		}
		System.out.printf("現在、%d勝%s敗です。\n", winCount, loseCount);
		return true;
	}

	protected boolean isEnd() throws IOException {
		System.out.println();
		System.out.println("もう一度やりますか？");
		System.out.println("続ける場合は何か入力してEnterを押して下さい。やめる場合はEnterのみを押して下さい。");

		String line = reader.readLine();
		if (line == null || line.isEmpty()) {
			System.out.println("終了します。");
			return true;
		}

		return false;
	}

	public static void main(String... args) throws IOException {
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
		new JankenExample3(reader).loop();
	}
}