JVM getObjectSize example

the simplest and the most efficient solution is to use very small sizeof library

<dependency>
    <groupId>com.carrotsearch</groupId>
    <artifactId>java-sizeof</artifactId>
    <version>0.0.3</version>
</dependency>

you need to use this http://grepcode.com/file/repo1.maven.org/maven2/com.carrotsearch/java-sizeof/0.0.2/com/carrotsearch/sizeof/RamUsageEstimator.java?av=f

shallowSizeOf() method or sizeOf()

That's really the simplest working fast solution i found on this topic so far...