月齢計算(calculate age of the moon)

MoonUtil.java

package daichan4649.moon;

public class MoonUtil {

    /**
     * 月齢取得
     * @param year 年(1, 2, ..)
     * @param month 月(1, 2, ..)
     * @param day 日(1, 2, ..)
     * @return 月齢
     * @see <a href="http://ja.wikipedia.org/wiki/%E6%9C%88%E9%BD%A2">月齢</a>
     */
    public static int calculateAgeOfTheMoon(int year, int month, int day) {
        return (((year - 11) % 19) * 11 + c(month) + day) % 30;
    }

    private static int c(int month) {
        switch (month) {
        case 1:
            return 0;
        case 2:
            return 2;
        case 3:
            return 0;
        case 4:
            return 2;
        case 5:
            return 2;
        case 6:
            return 4;
        case 7:
            return 5;
        case 8:
            return 6;
        case 9:
            return 7;
        case 10:
            return 8;
        case 11:
            return 9;
        case 12:
            return 10;
        }
        throw new RuntimeException(String.format("invalid value: %d", month));
    }

    /**
     * 月相種別取得
     * @param ageOfTheMoon 月齢
     * @return 月相種別
     * @see <a href="http://ja.wikipedia.org/wiki/%E6%9C%88%E7%9B%B8">月相</a>
     */
    public static LunarPhaseType getLunarPhaseType(int ageOfTheMoon) {
        switch (ageOfTheMoon) {
        case 0:
            // 新月(朔)
            return LunarPhaseType.NEW_MOON;
        case 7:
            // 上弦
            return LunarPhaseType.HALF_MOON_UP;
        case 14:
            // 満月(望)
            return LunarPhaseType.FULL_MOON;
        case 21:
            // 下弦
            return LunarPhaseType.HALF_MOON_DOWN;
        default:
            return LunarPhaseType.NONE;
        }
    }

    /**
     * 月相種別
     */
    public enum LunarPhaseType {
        NONE(""),
        NEW_MOON("新月"),
        HALF_MOON_UP("上弦"),
        HALF_MOON_DOWN("下弦"),
        FULL_MOON("満月");

        private String text;

        LunarPhaseType(String text) {
            this.text = text;
        }

        public String getText() {
            return text;
        }
    }
}

MoonUtilTest.java

package daichan4649.moon;

import junit.framework.Assert;
import junit.framework.TestCase;
import daichan4649.moon.MoonUtil.LunarPhaseType;

public class MoonUtilTest extends TestCase {

    public void testCalculateAgeOfTheMoon() {
        int year = 0;
        int month = 0;
        int day = 0;
        int expected = 0;
        int actual = 0;

        // 新月-1
        year = 2013;
        month = 8;
        day = 6;
        expected = 29;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 新月
        year = 2013;
        month = 8;
        day = 7;
        expected = 0;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 新月+1
        year = 2013;
        month = 8;
        day = 8;
        expected = 1;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 上弦-1
        year = 2013;
        month = 8;
        day = 13;
        expected = 6;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 上弦
        year = 2013;
        month = 8;
        day = 14;
        expected = 7;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 上弦+1
        year = 2013;
        month = 8;
        day = 15;
        expected = 8;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 満月-1
        year = 2013;
        month = 8;
        day = 20;
        expected = 13;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 満月
        year = 2013;
        month = 8;
        day = 21;
        expected = 14;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 満月+1
        year = 2013;
        month = 8;
        day = 22;
        expected = 15;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 下弦-1
        year = 2013;
        month = 8;
        day = 27;
        expected = 20;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 下弦
        year = 2013;
        month = 8;
        day = 28;
        expected = 21;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);

        // 下弦+1
        year = 2013;
        month = 8;
        day = 29;
        expected = 22;
        actual = MoonUtil.calculateAgeOfTheMoon(year, month, day);
        Assert.assertEquals(expected, actual);
    }

    public void testGetLunarPhaseType() {
        int ageOfTheMoon = 0;
        LunarPhaseType expected = LunarPhaseType.NONE;
        LunarPhaseType actual = LunarPhaseType.NONE;

        // 新月
        ageOfTheMoon = 0;
        expected = LunarPhaseType.NEW_MOON;
        actual = MoonUtil.getLunarPhaseType(ageOfTheMoon);
        Assert.assertEquals(expected, actual);

        // 上弦
        ageOfTheMoon = 7;
        expected = LunarPhaseType.HALF_MOON_UP;
        actual = MoonUtil.getLunarPhaseType(ageOfTheMoon);
        Assert.assertEquals(expected, actual);

        // 満月
        ageOfTheMoon = 14;
        expected = LunarPhaseType.FULL_MOON;
        actual = MoonUtil.getLunarPhaseType(ageOfTheMoon);
        Assert.assertEquals(expected, actual);

        // 下弦
        ageOfTheMoon = 21;
        expected = LunarPhaseType.HALF_MOON_DOWN;
        actual = MoonUtil.getLunarPhaseType(ageOfTheMoon);
        Assert.assertEquals(expected, actual);

        // 上記以外
        ageOfTheMoon = -1;
        expected = LunarPhaseType.NONE;
        actual = MoonUtil.getLunarPhaseType(ageOfTheMoon);
        Assert.assertEquals(expected, actual);

        ageOfTheMoon = 32;
        expected = LunarPhaseType.NONE;
        actual = MoonUtil.getLunarPhaseType(ageOfTheMoon);
        Assert.assertEquals(expected, actual);
    }
}