On Fri, 29 Apr 2022 06:31:22 GMT, Andrey Turbanov <aturba...@openjdk.org> wrote:
> `Map.containsKey` call is sometimes unnecessary, when it's known that Map
> doesn't contain `null` values.
> Instead we can just use Map.get and compare result with `null`.
> I found one of such place, where Map.containsKey calls could be eliminated -
> `java.time.format.ZoneName`.
> it gives a bit of performance for `toZid`.
>
>
> Benchmark Mode Cnt Score Error Units
> ZoneNamesBench.useExistingCountry avgt 5 10,738 ± 0,065 ns/op
> ZoneNamesBench.useExistingCountryOld avgt 5 13,679 ± 0,089 ns/op
>
>
> <details>
> <summary>Benchmark</summary>
>
>
> @BenchmarkMode(value = Mode.AverageTime)
> @OutputTimeUnit(TimeUnit.NANOSECONDS)
> @Warmup(iterations = 10, time = 1, timeUnit = TimeUnit.SECONDS)
> @Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
> @Fork(1)
> @State(Scope.Benchmark)
> public class ZoneNamesBench {
>
> @Benchmark
> public String useExistingCountry() {
> return ZoneName.toZid("Africa/Tunis", Locale.ITALY);
> }
>
> @Benchmark
> public String useExistingCountryOld() {
> return ZoneName.toZidOld("Africa/Tunis", Locale.ITALY);
> }
> }
>
>
>
> public static String toZid(String zid, Locale locale) {
> String mzone = zidToMzone.get(zid);
> if (mzone == null) {
> String alias = aliases.get(zid);
> if (alias != null) {
> zid = alias;
> mzone = zidToMzone.get(zid);
> }
> }
> if (mzone != null) {
> Map<String, String> map = mzoneToZidL.get(mzone);
> if (map == null || ((zid = map.get(locale.getCountry())) ==
> null)) {
> zid = mzoneToZid.get(mzone);
> }
> }
> return toZid(zid);
> }
>
> public static String toZid(String zid) {
> return aliases.getOrDefault(zid, zid);
> }
>
> public static String toZidOld(String zid, Locale locale) {
> String mzone = zidToMzone.get(zid);
> if (mzone == null && aliases.containsKey(zid)) {
> zid = aliases.get(zid);
> mzone = zidToMzone.get(zid);
> }
> if (mzone != null) {
> Map<String, String> map = mzoneToZidL.get(mzone);
> if (map != null && map.containsKey(locale.getCountry())) {
> zid = map.get(locale.getCountry());
> } else {
> zid = mzoneToZid.get(mzone);
> }
> }
> return toZidOld(zid);
> }
>
> public static String toZidOld(String zid) {
> if (aliases.containsKey(zid)) {
> return aliases.get(zid);
> }
> return zid;
> }
>
> </details>
src/java.base/share/classes/java/time/format/ZoneName.java.template line 60:
> 58:
> 59: public static String toZid(String zid) {
> 60: return aliases.getOrDefault(zid, zid);
Is the behavior if zid == null the same? aliases.getOrDefault will throw NPE
on null.
neither Hashmap.containsKey or .get throw on null.
-------------
PR: https://git.openjdk.java.net/jdk/pull/8463
