On Thu, 31 Mar 2022 08:03:23 GMT, Andrey Turbanov <aturba...@openjdk.org> 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
>
> Andrey Turbanov has updated the pull request incrementally with one
> additional commit since the last revision:
>
> 8280035: Use Class.isInstance instead of Class.isAssignableFrom where
> applicable
> apply suggestion to avoid second Method.invoke call
Thank you for review!
-------------
PR: https://git.openjdk.java.net/jdk/pull/7061
