Java 8 - Difference between Optional.flatMap and Optional.map

问题：

What's the difference between these two methods: Optional.flatMap() and Optional.map() ?这两种方法有什么区别： Optional.flatMap()和Optional.map() ？

An example would be appreciated.一个例子将不胜感激。

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解决方案：

参考一： https://en.stackoom.com/question/25VHr
参考二： https://stackoom.com/question/25VHr