== bytes per instance (= #bytes / #instances) from jcmd GC.class_histogram after loading 2,000,000 products
class                                    JDK 26 default JDK 27 default JDK 27 opt-out
com.ankurm.memory.Product                          40.0           32.0           40.0
java.util.HashMap$Node                             32.0           24.0           32.0
java.lang.Long                                     24.0           16.0           24.0
java.lang.String                                   24.0           24.0           24.0
[B                                                 32.7           32.6           32.7

== total bytes of those five classes
jdk26-default    309088088 bytes (294.8 MB)
jdk27-default    260853264 bytes (248.8 MB)
jdk27-optout     309272896 bytes (294.9 MB)