lamda -- 两个集合的各种问题处理

引入jar文件

<dependency>
	<groupId>com.google.guava</groupId>
	<artifactId>guava</artifactId>
	<version>20.0</version>
</dependency>

<dependency>
	<groupId>commons-lang</groupId>
	<artifactId>commons-lang</artifactId>
	<version>2.6</version>
</dependency>

LamdaMoreList.java

package com.example.demo.util;

import com.example.demo.entity.Student;
import com.example.demo.entity.User;
import com.example.demo.entity.UserDTO;
import com.example.demo.entity.UserPO;
import com.google.common.collect.Lists;
import org.apache.commons.lang.StringUtils;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;

public class LamdaMoreList {
   
   

    /**
     * List<PO> 转 List<DTO>
     */
    public static void test1() {
   
   
        //1. 初始化数据
        UserPO user1 = new UserPO(1, "java");
        UserPO user2 = new UserPO(2, "C");
        UserPO user3 = new UserPO(3, "PHP");
        List<UserPO> users = new ArrayList<>();
        users.add(user1);
        users.add(user2);
        users.add(user3);

        //2. List<PO> 转 List<DTO>
        List<UserDTO> dtoList = users.stream().map(getParamConverter()).collect(Collectors.toList());
        System.out.println(dtoList);
    }

    private static Function<UserPO, UserDTO> getParamConverter(){
   
   
        return userPO -> {
   
   
            UserDTO dto = new UserDTO();
            dto.setId(userPO.getId());
            dto.setName(userPO.getName());
            return dto;
        };
    }

    /**
     * List<String> 转 List<Integer>
     */
    public static void test2() {
   
   
        //1. 初始化List<String>
        String nums = "100,101,102,103,104";
        List<String> numStrList = Arrays.asList(nums.split<