I wonder why the new C implementation is faster on Android than the old Java implementation, even though the former comes with some overhead for JNI and the ina

I wonder why the new C implementation is faster on Android than the old Java implementation, even though the former comes with some overhead for JNI and the inability for the ART ahead-of-time compiler to do any cross-module optimziation between Java and native code. Is it because C has structs, which java still doesn't have?