On Thu, 13 Jan 2022 08:39:04 GMT, Andrey Turbanov <d...@openjdk.java.net> wrote:
>> Method `Class.isAssignableFrom` is often used in form of: >> >> if (clazz.isAssignableFrom(obj.getClass())) { >> Such condition could be simplified to more shorter and performarnt code >> >> if (clazz.isInstance(obj)) { >> >> Replacement is equivalent if it's known that `obj != null`. >> In JDK codebase there are many such places. >> >> I tried to measure performance via JMH >> >> Class<?> integerClass = Integer.class; >> Class<?> numberClass = Number.class; >> >> Object integerObject = 45666; >> Object doubleObject = 8777d; >> >> @Benchmark >> public boolean integerInteger_isInstance() { >> return integerClass.isInstance(integerObject); >> } >> >> @Benchmark >> public boolean integerInteger_isAssignableFrom() { >> return integerClass.isAssignableFrom(integerObject.getClass()); >> } >> >> @Benchmark >> public boolean integerDouble_isInstance() { >> return integerClass.isInstance(doubleObject); >> } >> >> @Benchmark >> public boolean integerDouble_isAssignableFrom() { >> return integerClass.isAssignableFrom(doubleObject.getClass()); >> } >> >> @Benchmark >> public boolean numberDouble_isInstance() { >> return numberClass.isInstance(doubleObject); >> } >> >> @Benchmark >> public boolean numberDouble_isAssignableFrom() { >> return numberClass.isAssignableFrom(doubleObject.getClass()); >> } >> >> @Benchmark >> public boolean numberInteger_isInstance() { >> return numberClass.isInstance(integerObject); >> } >> >> @Benchmark >> public boolean numberInteger_isAssignableFrom() { >> return numberClass.isAssignableFrom(integerObject.getClass()); >> } >> >> @Benchmark >> public void numberIntegerDouble_isInstance(Blackhole bh) { >> bh.consume(numberClass.isInstance(integerObject)); >> bh.consume(numberClass.isInstance(doubleObject)); >> } >> >> @Benchmark >> public void integerIntegerDouble_isAssignableFrom(Blackhole bh) { >> bh.consume(integerClass.isAssignableFrom(integerObject.getClass())); >> bh.consume(integerClass.isAssignableFrom(doubleObject.getClass())); >> } >> >> `isInstance` is a bit faster than `isAssignableFrom` >> >> Benchmark Mode Cnt Score Error Units >> integerDouble_isAssignableFrom avgt 5 1,173 ± 0,026 ns/op >> integerDouble_isInstance avgt 5 0,939 ± 0,038 ns/op >> integerIntegerDouble_isAssignableFrom avgt 5 2,106 ± 0,068 ns/op >> numberIntegerDouble_isInstance avgt 5 1,516 ± 0,046 ns/op >> integerInteger_isAssignableFrom avgt 5 1,175 ± 0,029 ns/op >> integerInteger_isInstance avgt 5 0,886 ± 0,017 ns/op >> numberDouble_isAssignableFrom avgt 5 1,172 ± 0,007 ns/op >> numberDouble_isInstance avgt 5 0,891 ± 0,030 ns/op >> numberInteger_isAssignableFrom avgt 5 1,169 ± 0,014 ns/op >> numberInteger_isInstance avgt 5 0,887 ± 0,016 ns/op > > src/jdk.jfr/share/classes/jdk/jfr/internal/TypeLibrary.java line 405: > >> 403: Object res = m.invoke(a, new Object[0]); >> 404: if (res instanceof Annotation[]) { >> 405: for (Annotation rep : (Annotation[]) >> m.invoke(a, new Object[0])) { > > BTW it looks suspicious to have `m.invoke(a, new Object[0])` called again > here. Shouldn't it just reuse `res` variable instead? It looks unnecessary. Please feel free to fix. ------------- PR: https://git.openjdk.java.net/jdk/pull/7061