java方法返回值的变量类型困惑

一、java program progress of excuting：show in next picture

       How about the java virtual machine is it,what situation is in the jvm,or how to worke is going?

       If you want to slove these questions,please read the next picture:

The more details please visit:http://aofengblog.blog.163.com/blog/static/631702120107142336862/

二、Why can java return local varieties?

     
As we known that the local varieties are stored in the stack(global varieties are in dull),and they will be destroyed when the method excuted.

     then my confuse also conducted,although this local varieties have been destroyed,i understand that the varieties of method in jvm had been clear,then,why could not void method return a local variety?

就是为什么java非空method能够返回method的局部变量，而不是必须是成员变量？