在对象访问速度，内存利用率和Java芯片系统复杂度之间合理折衷。
A perfect tradeoff will be gained among the object accessing performance, the memory utilization and the Java chip system simplicity.
增加自动对象实例变量打包(automatic object ivar packing)功能(提升内存利用率)。
延迟加载：它的目的是优化数据服务器的内存利用率，当程序启动后优先加载那些需要加入到内存的对象，不需要加载的推后加载。
Lazy loading: The purpose of lazy loading is to optimize memory utilization of database servers by prioritizing components that need to be loaded into memory when a program is started.
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