Optimize ThreadLocalCache while perusal the code.

I knew the library from an article in CSDN, then I began to perusal the implementation.
Besides learning some good techniques I also found some segment could be optimizing.
Hope this pull can be merged. If so, I can keep an eye on this repo and try to contributing some snippets in my spare time.
(I like elegant code but I hate alibaba, lol)

Best Regards!
Zhangbohong GAO
git: ttoommbb    gaozone-talend
mail:  ttoommbb#126.com    gaozone217#gmail.com