import com.yang.test.User;

import javax.jws.soap.SOAPBinding;
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;

public class Main {

    public static void main(String[] args) {

        List<User> userlist = new ArrayList<>();
        for (int i = 0; i <10; i++) {

            userlist.add(new User("張三"+i,i));
        }
        System.out.println(getAllages(userlist).size());

        System.out.println(getUser2Map(userlist));

        System.out.println(getUser2MapUser(userlist));

        System.out.println(getUser2MapUser2(userlist));

          System.out.println(getUser2MapUser3(userlist));

    }

    public static List<Integer> getAllages(List<User>userlist){
        return  userlist.stream().map(user -> user.getAge()).collect(Collectors.toList());
    }

    public static Map<Integer,String> getUser2Map(List<User>userlist){

        return userlist.stream().collect(Collectors.toMap(User::getAge,User::getName));
    }

    public static Map<Integer,User> getUser2MapUser(List<User>userlist){

        return userlist.stream().collect(Collectors.toMap(User::getAge,User-> User));
    }

    /**
     * 比較優雅的寫法是這樣的
     * @param userlist
     * @return
     */
    public static Map<Integer,User> getUser2MapUser2(List<User>userlist){

        return userlist.stream().collect(Collectors.toMap(User::getAge, Function.identity()));
    }

    /**
     * 重複key的情況下 簡單的使用後者覆蓋前者的
     */
    public static Map<Integer,User> getUser2MapUser3(List<User>userlist){

        return userlist.stream().collect(Collectors.toMap(User::getAge, Function.identity(),(key1,key2)->key2));
    }

    /**
     *指定map的具體實現
     * @param userlist
     * @return
     */
    public static Map<Integer,User> getUser2MapUser4(List<User>userlist){

        return userlist.stream().collect(Collectors.toMap(User::getAge, Function.identity(),(key1,key2)->key2, LinkedHashMap::new));
    }
}