Update README.md

Author: basahota

README.md

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 # java8
 Java 8 features
+
+Differences between Java 8 Map() Vs flatMap() :
+
+map() | flatMap() | 
+--- | --- |  
+It processes stream of values. | It processes stream of stream of values. 
+It does only mapping. | It performs mapping as well as flattening.
+It’s mapper function produces single value for each input value. | It’s mapper function produces multiple values for each input value. 
+It is a One-To-One mapping. | It is a One-To-Many mapping. 
+Data Transformation : From Stream<T> to Stream<R> | Data Transformation : From Stream<Stream<T> to Stream<R> 
+Use this method when the mapper function is producing a single value for each input value. | Use this method when the mapper function is producing multiple values for each input value. 
+