java 集合里的元素是集合，怎么遍历里面的集合？

Question

List list = new ArrayList();List<User> userList = new ArrayList();//用于接收从数据库查出的数据List<Department> dpList = new ArrayList();//用于接收从数据库查出的数据list.add(userList);list.add(dpList);需要将list传到另个方法里怎么用list遍历userList和dpList？

Answer 1

怎么遍历list 就怎么遍历 userList

Answer 2

foreach（var n in list.userlist）{}

foreach（var m in list.dpList）{}

Answer 3

这是什么东西？为啥还有var？

Answer 4

for(int i=0;i<list.size();i++){

　　List l = list.get(i);

　　for(Object o:l){

　　　　

if(o instanceof User){
User user = (User) o;
System.out.println(user);
}
if(o instanceof Department){
Department dep = (Department) o;
System.out.println(dep);
}

　　}

}

Answer 5

这跟楼上讲的差不多，我按楼上的思路写出来了，嘿嘿

Answer 6

你可以把两个list放在map里，不一定要放在list里，传一个map就好了...

Answer 7

 1 public class MyTests
 2 {
 3     public static void main(String[] args)
 4     {
 5         List<List<Reportable>> reportables = new ArrayList<List<Reportable>>();
 6         
 7         List<Reportable> users = new ArrayList<Reportable>();
 8         users.add(new User());
 9         users.add(new User());
10         users.add(new User());
11         
12         List<Reportable> departments = new ArrayList<Reportable>();
13         departments.add(new Department());
14         departments.add(new Department());
15         departments.add(new Department());
16         
17         reportables.add(users);
18         reportables.add(departments);
19         
20         for (List<Reportable> reports : reportables)
21         {
22             for (Reportable element : reports)
23             {
24                 element.printMe();
25             }
26         }
27     }
28 }
29 
30 interface Reportable
31 {
32     public void printMe();
33 }
34 
35 class User implements Reportable
36 {
37     @Override
38     public void printMe()
39     {
40         System.out.println("I am a user.");
41     }
42 }
43 
44 class Department implements Reportable
45 {
46     @Override
47     public void printMe()
48     {
49         System.out.println("I am a department");
50     }
51 }