Apply suggestions from code review

Co-authored-by: Bogdan Pintea <[email protected]>

Author: kanoshiou

server/src/main/java/org/elasticsearch/common/Rounding.java

@@ -83,10 +83,9 @@ long extraLocalOffsetLookup() {
             private final long extraLocalOffsetLookup = TimeUnit.DAYS.toMillis(92);
 
             long roundFloor(long utcMillis, int multiplier) {
-                if (multiplier == 1) {
-                    return DateUtils.roundQuarterOfYear(utcMillis);
-                }
-                return DateUtils.roundIntervalMonthOfYear(utcMillis, multiplier * 3);
+                return multiplier == 1
+                    ? DateUtils.roundQuarterOfYear(utcMillis)
+                    : DateUtils.roundIntervalMonthOfYear(utcMillis, multiplier * 3);
             }
 
             long extraLocalOffsetLookup() {

server/src/main/java/org/elasticsearch/common/time/DateUtils.java

@@ -374,7 +374,7 @@ public static long roundMonthOfYear(final long utcMillis) {
      */
     public static long roundIntervalMonthOfYear(final long utcMillis, final int monthInterval) {
         if (monthInterval <= 0) {
-            throw new IllegalArgumentException("month interval [" + monthInterval + "] must be positive");
+            throw new IllegalArgumentException("month interval must be strictly positive, got  [" + monthInterval + "]");
         }
         int year = getYear(utcMillis);
         int month = getMonthOfYear(utcMillis, year);
@@ -403,7 +403,7 @@ public static long roundYearInterval(final long utcMillis, final int yearInterva
             throw new IllegalArgumentException("year interval [" + yearInterval + "] must be positive");
         }
         int year = getYear(utcMillis);
-        return utcMillisAtStartOfYear((year - 1) / yearInterval * yearInterval + 1);
+        return utcMillisAtStartOfYear(((year - 1) / yearInterval) * yearInterval + 1);
     }
 
     /**