Java中如何使用flatMap呢?

flatMap的功能

flatMap:
   对流中每个元素进行平铺后
   形成多个流,然后合在一起

import java.io.*;
import java.util.*;
import java.util.Arraylist;
import java.util.List;
import java.util.stream.Collectors;
class TestClass {
    public static void main(String[] args)
    {
        // making the ArrayList object of List of Integer
        List<List<Integer> > number = new ArrayList<>();

        // adding the elements to number arraylist
        number.add(Arrays.asList(1, 2));
        number.add(Arrays.asList(3, 4));
        number.add(Arrays.asList(5, 6));
        number.add(Arrays.asList(7, 8));

        System.out.println("List of list-" + number);

        // using flatmap() to flatten this list
        List<Integer> flatList = number.stream().flatMap(list -> list.stream()).collect(Collectors.toList());

        // printing the list
        System.out.println("List generate by flatMap-" + flatList);
    }
}

//运行以上代码，将输出以下信息
List of list-[[1, 2], [3, 4], [5, 6], [7, 8]] 
List generate by flatMap-[1, 2, 3, 4, 5, 6, 7, 8]