Added method to get the length of day

caarmen · Jan 1, 2017 · 21b84ec · 21b84ec
1 parent c39d43d
commit 21b84ec
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Showing 4 changed files with 42 additions and 0 deletions.
diff --git a/cli/src/main/java/ca/rmen/sunrisesunset/cli/SunriseSunsetCLI.java b/cli/src/main/java/ca/rmen/sunrisesunset/cli/SunriseSunsetCLI.java
@@ -59,6 +59,8 @@ public static void main(String[] args) throws Throwable {
 		printCalendar(tz, now);
 
 		System.out.println("Current day period is " + SunriseSunset.getDayPeriod(now, latitude, longitude));
+		long dayLength = SunriseSunset.getDayLength(now, latitude, longitude);
+		System.out.println("Day is " + dayLength + " seconds long");
 
 		System.out.println("Lookup for date:");
 		printCalendar(tz, day);

diff --git a/library/src/main/java/ca/rmen/sunrisesunset/SunriseSunset.java b/library/src/main/java/ca/rmen/sunrisesunset/SunriseSunset.java
@@ -67,6 +67,7 @@ public enum DayPeriod {
 	private static final int JULIAN_DATE_2000_01_01 = 2451545;
 	private static final double CONST_0009 = 0.0009;
 	private static final double CONST_360 = 360;
+	private static final long SECONDS_IN_DAY = 60 * 60 * 24;
 
 	/**
 	 * Intermediate variables used in the sunrise equation
@@ -633,4 +634,32 @@ public static DayPeriod getDayPeriod(Calendar calendar, double latitude, double
 		return DayPeriod.NIGHT;
 	}
 
+	/**
+	 *
+	 * @param calendar the datetime for which to determine the day length
+	 * @param latitude  the latitude of the location in degrees.
+	 * @param longitude the longitude of the location in degrees (West is negative)
+     * @return the number of milliseconds between sunrise and sunset.
+     */
+	public static long getDayLength(Calendar calendar, double latitude, double longitude) {
+		Calendar[] sunriseSunset = getSunriseSunset(calendar, latitude, longitude);
+		if (sunriseSunset == null) {
+			int month = calendar.get(Calendar.MONTH); // Reminder: January = 0
+			if (latitude > 0) {
+				if (month >= 3 && month <= 10) {
+					return SECONDS_IN_DAY; // Always day at the north pole in June
+				} else {
+					return 0; // Always night at the north pole in December
+				}
+			} else {
+				if (month >= 3 && month <= 10) {
+					return 0; // Always night at the south pole in June
+				} else {
+					return SECONDS_IN_DAY; // Always day at the south pole in December
+				}
+			}
+		}
+		return (sunriseSunset[1].getTimeInMillis() - sunriseSunset[0].getTimeInMillis()) / 1000;
+	}
+
 }
diff --git a/library/src/test/java/ca/rmen/sunrisesunset/test/SunriseSunsetSpecificLocationsTest.java b/library/src/test/java/ca/rmen/sunrisesunset/test/SunriseSunsetSpecificLocationsTest.java
@@ -21,6 +21,7 @@
 package ca.rmen.sunrisesunset.test;
 
 import ca.rmen.sunrisesunset.SunriseSunset;
+import org.junit.Assert;
 import org.junit.Test;
 
 /**
@@ -59,6 +60,7 @@ public void testAntarctica() {
         SunriseSunsetTestUtils.testGetDayPeriod("Antarctica/McMurdo", "20150621 11:35", -77.8456, 166.6693, SunriseSunset.DayPeriod.NIGHT);
         SunriseSunsetTestUtils.testGetDayPeriod("Antarctica/McMurdo", "20150621 13:35", -77.8456, 166.6693, SunriseSunset.DayPeriod.NIGHT);
         SunriseSunsetTestUtils.testGetDayPeriod("Antarctica/McMurdo", "20150621 15:35", -77.8456, 166.6693, SunriseSunset.DayPeriod.ASTRONOMICAL_TWILIGHT);
+        SunriseSunsetTestUtils.testDayLength("Antarctica/McMurdo", "20150621", -77.8456, 166.6693, 0);
 
         SunriseSunsetTestUtils.testSunriseSunset("Antarctica/McMurdo", "20150921", -77.8456, 166.6693, "06:48", "18:46", accuracyMinutes);
         SunriseSunsetTwilightTestUtils.testCivilTwilight("Antarctica/McMurdo", "20150921", -77.8456, 166.6693, "5:07", "20:27", accuracyMinutes);
@@ -92,6 +94,7 @@ public void testAntarctica() {
         SunriseSunsetTestUtils.testGetDayPeriod("Antarctica/McMurdo", "20151221 12:00", -77.8456, 166.6693, SunriseSunset.DayPeriod.DAY);
         SunriseSunsetTestUtils.testGetDayPeriod("Antarctica/McMurdo", "20151221 18:00", -77.8456, 166.6693, SunriseSunset.DayPeriod.DAY);
         SunriseSunsetTestUtils.testGetDayPeriod("Antarctica/McMurdo", "20151221 23:00", -77.8456, 166.6693, SunriseSunset.DayPeriod.DAY);
+        SunriseSunsetTestUtils.testDayLength("Antarctica/McMurdo", "20151221", -77.8456, 166.6693, 86400);
 
     }
 

diff --git a/library/src/test/java/ca/rmen/sunrisesunset/test/SunriseSunsetTestUtils.java b/library/src/test/java/ca/rmen/sunrisesunset/test/SunriseSunsetTestUtils.java
@@ -206,6 +206,14 @@ static void testSolarNoon(String timeZoneString,
         validateSolarNoon(actualSolarNoon, timeZoneString, inputDayString, expectedNoonString);
     }
 
+    static void testDayLength(String timeZoneString,
+                              String inputDayString, double inputLatitude, double inputLongitude,
+                              long expectedDayLength) {
+
+        Calendar inputDay = parseDate(timeZoneString, inputDayString);
+        Assert.assertEquals(expectedDayLength, SunriseSunset.getDayLength(inputDay, inputLatitude, inputLongitude));
+    }
+
     static Calendar parseDate(String timeZoneString, String inputDayString) {
         TimeZone tz = TimeZone.getTimeZone(timeZoneString);