Merge pull request h2database#163 from stevemcleod/datetimeutils_tweak

In DateTimeUtils.getTimeTry(), Calendar instances used to evaluate Timestamps were only being cached if no timezone was specified. I've added code to reuse Calendar instances if the timezone specified matches the previous use.

Author: thomasmueller

h2/src/main/org/h2/util/DateTimeUtils.java

@@ -62,6 +62,12 @@ public class DateTimeUtils {
     private static final ThreadLocal<Calendar> CACHED_CALENDAR =
             new ThreadLocal<Calendar>();
 
+    /**
+     * A cached instance of Calendar used when a timezone is specified.
+     */
+    private static final ThreadLocal<Calendar> CACHED_CALENDAR_NON_DEFAULT_TIMEZONE =
+            new ThreadLocal<Calendar>();
+
     private DateTimeUtils() {
         // utility class
     }
@@ -82,6 +88,19 @@ private static Calendar getCalendar() {
         return c;
     }
 
+    /**
+     * @param tz timezone for the calendar, is never null
+     * @return a calendar instance for the specified timezone. A cached instance is returned where possible
+     */
+    private static Calendar getCalendar(TimeZone tz) {
+        Calendar c = CACHED_CALENDAR_NON_DEFAULT_TIMEZONE.get();
+        if (c == null || !c.getTimeZone().equals(tz)) {
+            c = Calendar.getInstance(tz);
+            CACHED_CALENDAR_NON_DEFAULT_TIMEZONE.set(c);
+        }
+        return c;
+    }
+
     /**
      * Convert the date to the specified time zone.
      *
@@ -394,7 +413,7 @@ private static long getTimeTry(boolean lenient, TimeZone tz,
         if (tz == null) {
             c = getCalendar();
         } else {
-            c = Calendar.getInstance(tz);
+            c = getCalendar(tz);
         }
         c.clear();
         c.setLenient(lenient);