Serialized object size vs in memory object size in Java

Question

Is there a way of estimating (roughly) in memory object size from Serialized object size in Java

Answer 1

A very nice Tool for this challenge: https://github.com/jbellis/jamm

From the readme.txt:

MemoryMeter is as accurate as java.lang.instrument.Instrumentation.getObjectSize, which only claims to provide "approximate" results, but in practice seems to work as expected.

MemoryMeter uses reflection to crawl the object graph for measureDeep. Reflection is slow: measuring a one-million object Cassandra Memtable (that is, 1 million children from MemoryMeter.countChildren) took about 5 seconds wall clock time.