1.instrumentation这种方法还是靠谱的
一个对象占用多少字节？
2.sizeof库
<!-- https://mvnrepository.com/artifact/com.carrotsearch/java-sizeof -->
<dependency>
<groupId>com.carrotsearch</groupId>
<artifactId>java-sizeof</artifactId>
<version>0.0.5</version>
</dependency>
3.