:https://stackoverflow.com/questions/26684562/whats-the-difference-between-map-and-flatmap-methods-in-java-8 [2]flatMap() Method in Java 8 :https://www.javatpoint.com/flatmap-method-in-java-8
Map Methods The Map object includes several methods, which are tabulated as follows: Map对象包括几种方法,其列表如下: Weak Maps Weak Maps are almost similar to normal Maps except that the keys in weak maps must be objects. It stores each element as a key-value pair where keys are weakly r...