Java 8 Stream Convert List<List<String>> to List<String>
摘要: As title, we can use flatMap to convert it.
As title, we can use flatMap to convert it.
Java9Example1.java
package com.mkyong.test;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;
public class Java9Example1 {
public static void main(String[] args) {
List<String> numbers = Arrays.asList("1", "2", "A", "B", "C1D2E3");
List<List<String>> collect = numbers.stream()
.map(x -> new Scanner(x).findAll("\\D+")
.map(m -> m.group())
.collect(Collectors.toList())
.collect(Collectors.toList());
collect.forEach(x -> System.out.println(x));
Output
[] [] [A] [B] [C, D, E]
Solution
Java9Example2.java
package com.mkyong.test;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;
public class Java9Example2 {
public static void main(String[] args) {
List<String> numbers = Arrays.asList("1", "2", "A", "B", "C1D2E3");
List<String> collect = numbers.stream()
.map(x -> new Scanner(x).findAll("\\D+")
.map(m -> m.group())
.collect(Collectors.toList())
) // List<List<String>>
.flatMap(List::stream) // List<String>
.collect(Collectors.toList());
collect.forEach(x -> System.out.println(x));
Output
