报错

package com.test;

import java.util.*;
class User{
    public String name;
    public Integer age;

    public boolean equals(Object obj) {//重写 对比函数
        if(obj instanceof User) {
            User u = (User)obj;
            return this.name.equals(u.name) && this.age.equals(u.age);
        }
        return super.equals(obj);
    }
}

public class Demo1 {

    public static void main(String[] args) {
        // TODO 自动生成的方法存根
        ArrayList<User> list = new ArrayList<>();

        // 开启后报错
//      for(int i = 1; i <= 3; i++) {
//          Scanner scanner = new Scanner(System.in);
//          User user = new User();
//          System.out.println("请输入用户信息");
//          System.out.println("姓名");
//          user.name = scanner.nextLine();
//          System.out.println("密码");
//          user.age = scanner.nextInt();
//          list.add(user);
//          scanner.close();
//      }

        // 普通 1
        Scanner scanner = new Scanner(System.in);
        User user_a = new User();
        User user_b = new User();
        User user_c = new User();

        System.out.println("请输入用户信息");
        System.out.println("姓名");
        user_a.name = scanner.nextLine();
        System.out.println("密码");
        user_a.age = scanner.nextInt();
        list.add(user_a);


        //System.out.println("请输入用户信息");
        System.out.println("姓名");
        user_b.name = scanner.nextLine();
        System.out.println("密码");
        user_b.age = scanner.nextInt();
        list.add(user_b);


        //System.out.println("请输入用户信息");
        System.out.println("姓名");
        user_c.name = scanner.nextLine();
        System.out.println("密码");
        user_c.age = scanner.nextInt();
        list.add(user_c);

        scanner.close();
        // 普通2
        User user1 = new User();
        user1.name = "景山";
        user1.age = 33;
        list.add(user1);
        User user2 = new User();
        user2.name = "景山";
        user2.age = 23;
        list.add(user2);
        User user3 = new User();
        user3.name = "景山";
        user3.age = 23;
        list.add(user3);        
        // 输出信息
        Iterator<User> iterator = list.iterator();
        while(iterator.hasNext()) {
            User u = (User)iterator.next();
            System.out.println(u.name);
            System.out.println(u.age);
        }
        System.out.println("去掉重复后的结果");
        // 手工去掉重复
        List<User> list1 = getList(list);
        Iterator<User> iterator1 = list1.iterator();
        while(iterator1.hasNext()) {
            User u = (User)iterator1.next();
            System.out.println(u.name);
            System.out.println(u.age);
        }
    }
    // 去重函数
    public static List<User> getList(List<User> list) {
        List<User> listCopy = new ArrayList<User>();
        Iterator<User> iterator = list.iterator();
        while(iterator.hasNext()) {
            User u = (User)iterator.next();
            if(!listCopy.contains(u)) {
                listCopy.add(u);
            }
        }
        return listCopy;
    }

}