关于list一个很有意思的小题

package com.sdufe.domain;

import java.util.ArrayList;
import java.util.List;

class User {
 private int num;

 public User(int num) {
  this.num = num;
 }

 public int getNum() {
  return num;
 }

 public void setNum(int num) {
  this.num = num;
 }
}

public class test {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  List<User> userList = new ArrayList<User>();
  userList.add(new User(0));
  User user1 = new User(1);
  User user2=new User(2);
  userList.add(user1);
  userList.add(0, user2);
  System.out.println(userList);
  System.out.println(userList.size());
  for (User user : userList) {
   System.out.println("usernum==="+user.getNum());
  }
  
 }

}

问题：里面有几个User Instance  运行结果是什么

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不去跑你知道答案吗？

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