Make DateTimeType Comparable (#4364)

Signed-off-by: Jimmy Tanagra <jcode@tanagra.id.au>

bundles/org.openhab.core/src/main/java/org/openhab/core/library/types/DateTimeType.java

@@ -37,9 +37,10 @@ import org.openhab.core.types.State;
  * @author Wouter Born - increase parsing and formatting precision
  * @author Laurent Garnier - added methods toLocaleZone and toZone
  * @author Gaël L'hopital - added ability to use second and milliseconds unix time
+ * @author Jimmy Tanagra - implement Comparable
  */
 @NonNullByDefault
-public class DateTimeType implements PrimitiveType, State, Command {
+public class DateTimeType implements PrimitiveType, State, Command, Comparable<DateTimeType> {
 
     // external format patterns for output
     public static final String DATE_PATTERN = "yyyy-MM-dd'T'HH:mm:ss";
@@ -229,6 +230,11 @@ public class DateTimeType implements PrimitiveType, State, Command {
         return zonedDateTime.compareTo(other.zonedDateTime) == 0;
     }
 
+    @Override
+    public int compareTo(DateTimeType o) {
+        return zonedDateTime.compareTo(o.getZonedDateTime());
+    }
+
     private ZonedDateTime parse(String value) throws DateTimeParseException {
         ZonedDateTime date;
         try {

bundles/org.openhab.core/src/test/java/org/openhab/core/library/types/DateTimeTypeTest.java

@@ -248,6 +248,18 @@ public class DateTimeTypeTest {
         assertTrue(dt1.equals(dt2));
     }
 
+    @Test
+    public void comparabilityTest() {
+        ZonedDateTime zoned = ZonedDateTime.now();
+        DateTimeType dt1 = new DateTimeType(zoned);
+        DateTimeType dt2 = new DateTimeType(zoned.plusSeconds(1));
+        DateTimeType dt3 = new DateTimeType(zoned.minusSeconds(1));
+
+        assertTrue(dt1.compareTo(dt2) < 0);
+        assertTrue(dt1.compareTo(dt3) > 0);
+        assertTrue(dt1.compareTo(dt1) == 0);
+    }
+
     @Test
     public void zonedParsingTest() {
         DateTimeType dt1 = new DateTimeType("2019-06-12T17:30:00Z");