Adding toCalendar method per LANG-632

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@963601 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/lang3/time/DateUtils.java

@@ -621,6 +621,20 @@ private static Date set(Date date, int calendarField, int amount) {
         c.set(calendarField, amount);
         return c.getTime();
     }   
+
+    //-----------------------------------------------------------------------
+    /**
+     * Convert a Date into a Calendar object. 
+     * 
+     * @param date the date to convert to a Calendar
+     * @return the created Calendar
+     * @throws NullPointerException if null is passed in
+     */
+    public static Calendar toCalendar(Date date) {
+        Calendar c = Calendar.getInstance();
+        c.setTime(date);
+        return c;
+    }
     
     //-----------------------------------------------------------------------
     /**

src/test/java/org/apache/commons/lang3/time/DateUtilsTest.java

@@ -597,6 +597,17 @@ private void assertDate(Date date, int year, int month, int day, int hour, int m
         assertEquals(mil, cal.get(Calendar.MILLISECOND));
     }
 
+    //-----------------------------------------------------------------------
+    public void testToCalendar() {
+        assertEquals("Failed to convert to a Calendar and back", date1, DateUtils.toCalendar(date1).getTime());
+        try {
+            DateUtils.toCalendar(null);
+            fail("Expected NullPointerException to be thrown");
+        } catch(NullPointerException npe) {
+            // expected
+        }
+    }
+
     //-----------------------------------------------------------------------
     /**
      * Tests various values with the round method