TimeUnit.toMillis/toNanos/toMicros/toSeconds is shorter and a bit faster.
Compared via JMH benchmark: 150ns -> 125ns/op
<details>
<summary>Benchamark adapted from
http://cr.openjdk.java.net/~shade/8152083/TimeUnitBench.java</summary>
@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Fork(1)
@State(Scope.Thread)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class TimeUnitBench {
static final int SIZE = TimeUnit.values().length * 10;
@Param({"0", "1", "2", "3", "4", "5", "6", "-1"})
int bias;
TimeUnit[] mod;
@Setup
public void setup() {
mod = new TimeUnit[SIZE];
TimeUnit[] vals = TimeUnit.values();
for (int c = 0; c < SIZE; c++) {
if (bias == -1) {
// megamorphic
mod[c] = vals[c % vals.length];
} else {
mod[c] = vals[bias];
}
}
Random r = new Random();
for (int c = 0; c < 10000; c++) {
int i = r.nextInt();
for (int o = 0; o < vals.length; o++) {
if (vals[o].toNanos(i) != TimeUnit.NANOSECONDS.convert(i,
vals[o]))
throw new IllegalStateException("switch " + o);
}
}
}
@Benchmark
public void const_convert(Blackhole bh) {
for (TimeUnit tu : mod) {
bh.consume(do_convert(tu));
}
}
@Benchmark
public void value_convert(Blackhole bh) {
for (TimeUnit tu : mod) {
bh.consume(do_convert(tu, 1L));
}
}
@Benchmark
public void const_toNanos(Blackhole bh) {
for (TimeUnit tu : mod) {
bh.consume(do_toNanos(tu));
}
}
@Benchmark
public void value_toNanos(Blackhole bh) {
for (TimeUnit tu : mod) {
bh.consume(do_toNanos(tu, 1L));
}
}
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
private long do_toNanos(TimeUnit tu) {
return tu.toNanos(1L);
}
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
private long do_toNanos(TimeUnit tu, long value) {
return tu.toNanos(value);
}
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
private long do_convert(TimeUnit tu) {
return TimeUnit.NANOSECONDS.convert(1L, tu);
}
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
private long do_convert(TimeUnit tu, long value) {
return TimeUnit.NANOSECONDS.convert(value, tu);
}
}
Results:
Benchmark (bias) Mode Cnt Score Error Units
TimeUnitBench.const_convert 0 avgt 5 151,856 ± 28,595 ns/op
TimeUnitBench.const_convert 1 avgt 5 150,720 ± 23,863 ns/op
TimeUnitBench.const_convert 2 avgt 5 151,432 ± 23,184 ns/op
TimeUnitBench.const_convert 3 avgt 5 150,959 ± 24,726 ns/op
TimeUnitBench.const_convert 4 avgt 5 150,966 ± 25,280 ns/op
TimeUnitBench.const_convert 5 avgt 5 150,976 ± 25,542 ns/op
TimeUnitBench.const_convert 6 avgt 5 151,118 ± 25,254 ns/op
TimeUnitBench.const_convert -1 avgt 5 152,673 ± 29,861 ns/op
TimeUnitBench.const_toNanos 0 avgt 5 121,296 ± 25,236 ns/op
TimeUnitBench.const_toNanos 1 avgt 5 121,707 ± 25,364 ns/op
TimeUnitBench.const_toNanos 2 avgt 5 121,736 ± 25,726 ns/op
TimeUnitBench.const_toNanos 3 avgt 5 121,822 ± 25,491 ns/op
TimeUnitBench.const_toNanos 4 avgt 5 121,867 ± 26,090 ns/op
TimeUnitBench.const_toNanos 5 avgt 5 121,927 ± 25,611 ns/op
TimeUnitBench.const_toNanos 6 avgt 5 121,821 ± 25,843 ns/op
TimeUnitBench.const_toNanos -1 avgt 5 121,923 ± 25,206 ns/op
TimeUnitBench.value_convert 0 avgt 5 150,525 ± 25,439 ns/op
TimeUnitBench.value_convert 1 avgt 5 151,098 ± 24,024 ns/op
TimeUnitBench.value_convert 2 avgt 5 151,259 ± 25,381 ns/op
TimeUnitBench.value_convert 3 avgt 5 151,030 ± 25,548 ns/op
TimeUnitBench.value_convert 4 avgt 5 151,290 ± 25,998 ns/op
TimeUnitBench.value_convert 5 avgt 5 151,006 ± 25,448 ns/op
TimeUnitBench.value_convert 6 avgt 5 150,945 ± 25,314 ns/op
TimeUnitBench.value_convert -1 avgt 5 151,186 ± 25,814 ns/op
TimeUnitBench.value_toNanos 0 avgt 5 121,556 ± 25,745 ns/op
TimeUnitBench.value_toNanos 1 avgt 5 123,410 ± 22,323 ns/op
TimeUnitBench.value_toNanos 2 avgt 5 125,452 ± 26,575 ns/op
TimeUnitBench.value_toNanos 3 avgt 5 125,297 ± 26,204 ns/op
TimeUnitBench.value_toNanos 4 avgt 5 125,357 ± 26,085 ns/op
TimeUnitBench.value_toNanos 5 avgt 5 125,165 ± 26,185 ns/op
TimeUnitBench.value_toNanos 6 avgt 5 125,536 ± 25,487 ns/op
TimeUnitBench.value_toNanos -1 avgt 5 125,460 ± 25,063 ns/op
</details>
-------------
Commit messages:
- [PATCH] Simplify TimeUnit.convert calls to TimeUnit.toSomething instead
Changes: https://git.openjdk.java.net/jdk/pull/8376/files
Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8376&range=00
Issue: https://bugs.openjdk.java.net/browse/JDK-8285519
Stats: 30 lines in 7 files changed: 2 ins; 0 del; 28 mod
Patch: https://git.openjdk.java.net/jdk/pull/8376.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/8376/head:pull/8376
PR: https://git.openjdk.java.net/jdk/pull/8376
