Java中如何使用Lambda和stream的map()方法将对象转换为另一种类型呢?

对象转换方法

在Java8中,对象转换我们可以使用
    Lambda表达式中Stream对象的map()方法
	  可将对象转换为另一种类型

    <R>Stream <R> map(Function<? super T,? extends R> mapper)

import java.util.*;
import java.util.stream.*;

public class UserInformationTest {
   public static void main(String args[]) {
      list<User> Users = Arrays.asList(
         new User("maomao"),
         new User("adeal"),
         new User("java我最爱"));
      
	  //List 转 String的示例
      List<String> names = Users.stream()
         .map(s -> s.getUserName())//Lambda表达式
         .collect(Collectors.toList());
      System.out.println(names);
   }
}

//User类
class User {
   private String userName;
   private String userDesignation;
   public User(String userName) {
      this.userName = userName;
   }
   public String getUserName() {
      return userName;
   }
   public void setUserName(String userName) {
      this.userName = userName;
   }
   public String getUserDesignation() {
      return userDesignation;
   }
   public void setUserDesignation(String userDesignation) {
      this.userDesignation = userDesignation;
   }
}