Warnings Cleanup in java.util.<various> (more from hack day)

[Martijn Verburg]

Hi Sherman,

Thanks for sending that through - very interesting. I'll let Prasanna
know as well, especially with regards to the performance and GC
implications, I'm kicking myself for not having picked up on at least
on of those when reviewing :(.

I'll re-spin a patch (adding a @SuppressWarnings with a comment) and
get it sent through Mike Barker.

Cheers,
Martijn

> Hi Martijn,
>
> No, I don't think we have a benchmark test case anywhere in OpenJDK to
> measure this performance. I happened to take a quick look at the
> "calculation cost" of dosToJavaTime() last month when working on that
> jar n-thread performance issue.
>
> Here is a the result of a quick/dirty "non-benchmark" benchmark test case,
> which suggests the proposed change is way too slow, this is only from the
> "speed" angle,
>
> I would assume it probably also consumes more temporary (young-gen) memory.
> So, the suggested approach appears not to be a good candidate to go in
> without further tuning.
>
> sherman at sherman-linux:~/Workspace/test$ java -server JavaDosTime
> j2dt  :386
> j2dt2 :1282
> d2jt  :424
> d2jt2 :1296
> sherman at sherman-linux:~/Workspace/test$ java -client JavaDosTime
> j2dt  :621
> j2dt2 :1901
> d2jt  :662
> d2jt2 :2016
>
> public class JavaDosTime {
>
>     public static void main(String[] args) throws IOException {
>
>         long tt0 = System.currentTimeMillis();
>         int ii = 0;
>         for (ii = 0; ii < 1000000; ii++) {
>             long t = 10000 + ii;
>             t= javaToDosTime(t);
>         }
>         long tt1 = System.currentTimeMillis();
>         System.out.println("j2dt  :" + (tt1 - tt0));
>
>
>         tt0 = System.currentTimeMillis();
>         ii = 0;
>         for (ii = 0; ii < 1000000; ii++) {
>             long t = 10000 + ii;
>             t= javaToDosTime2(t);
>         }
>         tt1 = System.currentTimeMillis();
>         System.out.println("j2dt2 :" + (tt1 - tt0));
>
>
>         tt0 = System.currentTimeMillis();
>         ii = 0;
>         for (ii = 0; ii < 1000000; ii++) {
>             long t = 10000 + ii;
>             t= dosToJavaTime(t);
>         }
>         tt1 = System.currentTimeMillis();
>         System.out.println("d2jt  :" + (tt1 - tt0));
>
>
>         tt0 = System.currentTimeMillis();
>         ii = 0;
>         for (ii = 0; ii < 1000000; ii++) {
>             long t = 10000 + ii;
>             t= dosToJavaTime2(t);
>         }
>         tt1 = System.currentTimeMillis();
>         System.out.println("d2jt2 :" + (tt1 - tt0));
>
>     }
>
>     private static long javaToDosTime(long time){
>         Date d = new Date(time);
>         int year = d.getYear() + 1900;
>         if (year < 1980) {
>             return (1 << 21) | (1 << 16);
>         }
>         return (year - 1980) << 25 | (d.getMonth() + 1) << 21 |
>                d.getDate() << 16 | d.getHours() << 11 | d.getMinutes() << 5
> |
>                d.getSeconds() >> 1;
>     }
>
>     private static long javaToDosTime2(long time){
>         Calendar cal = Calendar.getInstance();
>         cal.setTimeInMillis(time);
>         int year = cal.get(Calendar.YEAR);
>         if (year < 1980) {
>             return (1 << 21) | (1 << 16);
>         }
>         int month = cal.get(Calendar.MONTH) + 1;
>         return (year - 1980) << 25
>                 | month << 21
>                 | cal.get(Calendar.DAY_OF_MONTH) << 16
>                 | cal.get(Calendar.HOUR_OF_DAY) << 11
>                 | cal.get(Calendar.MINUTE) << 5
>                 | cal.get(Calendar.SECOND) >> 1;
>      }
>
>      private static long dosToJavaTime(long dtime) {
>         Date d = new Date((int)(((dtime >> 25) & 0x7f) + 80),
>                           (int)(((dtime >> 21) & 0x0f) - 1),
>                           (int)((dtime >> 16) & 0x1f),
>                           (int)((dtime >> 11) & 0x1f),
>                           (int)((dtime >> 5) & 0x3f),
>                           (int)((dtime << 1) & 0x3e));
>         return d.getTime();
>      }
>
>      private static long dosToJavaTime2(long dtime) {
>      Calendar cal = Calendar.getInstance();
>      cal.set(Calendar.YEAR, (int) ((dtime >> 25) & 0x7f) + 1980);
>      cal.set(Calendar.MONTH, (int) ((dtime >> 21) & 0x0f) - 1);
>      cal.set(Calendar.DATE, (int) (dtime >> 16) & 0x1f);
>      cal.set(Calendar.HOUR_OF_DAY, (int) (dtime >> 11) & 0x1f);
>      cal.set(Calendar.MINUTE, (int) (dtime >> 5) & 0x3f);
>      cal.set(Calendar.SECOND, (int) (dtime << 1) & 0x3e);
>          return cal.getTimeInMillis();
>
>      }
> }