Stream FlatMap

The flatMap function defined in the Stream class is used to combine or merge multiple maps and apply the flat operations. It's an Intermediate function. it's majorly used for flating Collection of Collection or Stream of Stream to merge everything into a single result Stream

package org.wesome.java8;

import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.stream.Collectors;

class Apple {
    public static void main(String args[]) {
        List<Integer> listA = Arrays.asList(1, 2, 3, 4, 5);
        List<Integer> listB = Arrays.asList(6, 7, 8, 9, 10);
        List<Integer> listC = Arrays.asList(11, 12, 13, 14, 15);

        List<List<Integer>> list = Arrays.asList(listA, listB, listC);
        System.out.println("list = " + list);

        System.out.println("*---------------------------flatMap on List of Integers---------------------------*");
        List<Integer> flatMapInteger = list.stream().flatMap(Collection::stream).collect(Collectors.toList());
        System.out.println("flatMapInteger = " + flatMapInteger);

        System.out.println("*---------------------------flatMap on List of Integers with Map---------------------------*");
        List<Integer> flatMapAndMapInteger = list.stream().flatMap(Collection::stream).map(integer -> integer + 1).collect(Collectors.toList());
        System.out.println("flatMapAndMapInteger = " + flatMapAndMapInteger);

        System.out.println("*---------------------------flatMap on list of Strings---------------------------*");
        String[][] fruits = new String[][]{{"Apple", "Macintosh"}, {"Orange", "Valencia"}, {"Mango", "Alphonso"}, {"Avocado", "Hass"}};
        List<String> flatMapString = Arrays.stream(fruits).flatMap(Arrays::stream).collect(Collectors.toList());
        System.out.println("flatMapString = " + flatMapString);
    }
}