Benchmark to compare equals on Java records to Scala case classes.

• Java uses invokedynamic with java.lang.runtime.ObjectMethods
• Scala generates bytecode directly in equals

With JDK 16, sbt jmh:run:

...
[info] Bench.largeJavaEqualityTest     avgt  250   9.689 ± 0.140  ns/op
[info] Bench.largeJavaInequalityTest   avgt  250   2.949 ± 0.111  ns/op
[info] Bench.largeScalaEqualityTest    avgt  250  31.844 ± 0.352  ns/op
[info] Bench.largeScalaInequalityTest  avgt  250   7.203 ± 0.065  ns/op
[info] Bench.smallJavaEqualityTest     avgt  250   3.856 ± 0.043  ns/op
[info] Bench.smallJavaInequalityTest   avgt  250   3.234 ± 0.219  ns/op
[info] Bench.smallScalaEqualityTest    avgt  250   7.307 ± 0.112  ns/op
[info] Bench.smallScalaInequalityTest  avgt  250   3.473 ± 0.030  ns/op

Conclusion: Java wins in every dimension

• it is faster

• the bytecode for equals is much shorter (especially when you account for the fact the bootstrap method is re-used for hashCode and toString)

• the implementation of ObjectMethods is flexible, so can be improved in future JVMs without the bytecode invokedynamic call needing to change.