Create Doomsday.java

AtoMc · web-flow · commit 93c8c52d3d74 · 2017-10-10T17:31:19.000+02:00
diff --git a/Doomsday/Doomsday.java b/Doomsday/Doomsday.java
@@ -0,0 +1,58 @@
+/**
+ * Determines the day of the week.
+ * 
+ * @author Atom
+ *
+ */
+public class Doomsday {
+	
+	/**
+	 * Determines the day of the week using Tomohiko Sakamoto's Algorithm
+	 * to calculate Day of Week based on Gregorian calendar.
+	 * 
+	 * @param y year
+	 * @param m month
+	 * @param d day
+	 * @return day of the week (0 = sunday, 6 = saturday)
+	 */
+	public static int dow(int y, int m, int d) {
+		final int[] t = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
+		y -= (m < 3) ? 1 : 0;
+	    return (y + y/4 - y/100 + y/400 + t[m-1] + d) % 7;
+	}
+	
+	/**
+	 * Determines the day of the week using Tomohiko Sakamoto's Algorithm
+	 * to calculate Day of Week based on Gregorian calendar.
+	 * 
+	 * @param y year
+	 * @param m month
+	 * @param d day
+	 * @return day of the week
+	 */
+	public static String dowS(int y, int m, int d) {
+		switch (dow(y, m, d)) {
+			case 0: return "Sunday";
+			case 1: return "Monday";
+			case 2: return "Tuesday";
+			case 3: return "Wednesday";
+			case 4: return "Thursday";
+			case 5: return "Friday";
+			case 6: return "Saturday";
+			default:
+				System.out.println("Unknown dow");
+		}
+		return null;
+	}
+	
+	public static void main(String[] args) {
+		System.out.println(dow(1886, 5, 1) + ": " + dowS(1886, 5, 1));
+		System.out.println(dow(1948, 12, 10) + ": " + dowS(1948, 12, 10));
+		System.out.println(dow(2001, 1, 15) + ": " + dowS(2001, 1, 15));
+		System.out.println(dow(2017, 10, 10) + ": " + dowS(2017, 10, 10));
+		System.out.println(dow(2018, 1, 1) + ": " + dowS(2018, 1, 1));
+		System.out.println(dow(2018, 2, 16) + ": " + dowS(2018, 2, 16));
+		System.out.println(dow(2018, 5, 17) + ": " + dowS(2018, 5, 17));
+	}
+
+}
