java8 Optional正确使用姿勢

<a href="https://mp.weixin.qq.com/s?__biz=MjM5NzMyMjAwMA==&amp;mid=2651478860&amp;idx=2&amp;sn=b380f463c3f58a28bf988a7121e3629a&amp;chksm=bd2537338a52be253322525f7946302d3b2d4bf5a9b7789a66159c3793df71ba490207b69dee&amp;scene=0&amp;key=07ca847744b09018afdf187219dedaf984326997bff2ed8920028f75addb9c4f0495079be3f0b3f264d44b9500d9d783793274168f3875eaa8bda056d4c814c900ca87e225996bdf8ca9715d7ca6cabb&amp;ascene=0&amp;uin=MjI0MDkzMzAyNA%3D%3D&amp;devicetype=iMac+MacBookPro11%2C1+OSX+OSX+10.12.6+build(16G29)&amp;version=12020810&amp;nettype=WIFI&amp;fontScale=100&amp;pass_ticket=D03n9TeSJSL6iSWC8vJFxJe0YKhV5bUKSoCPEDAdaIcQZq4j4rp4hEvo3uKATKCT">Java 8 如何正确使用 Optional</a>