What is flatMap() ? Write code for flatMap.

 Interview Question

Q. What is flatMap() ? Write code for flatMap.

Ans:- 

flatMap()  :- flatMap()  transform each element and flattern the resulting collection into a single combined collection.

Example of flatMap():-

package v1;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.stream.Collectors;

public class FlatMapExample {

public static void main(String[] args) {

List<List<Integer>> list=new ArrayList<>();

list.add(Arrays.asList(1,2,3));

list.add(Arrays.asList(4,5,6));

list.add(Arrays.asList(7,8,9));

System.out.println(list);

List<Integer> flatList=list.stream().flatMap(i->i.stream().map(j->j*2)).collect(Collectors.toList());

System.out.println("FlatList:"+flatList);

}

}

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