java集合工具类的使用

Question

package com;

import java.util.ArrayList;
import java.util.Collections;

public class CollectionDemo {

public static void main(String[] args) {
    ArrayList<Person> list = new ArrayList<Person>();
    list.add(new Person("张三", 13, "北京"));
    list.add(new Person("李四", 8, "上海"));
}

}
请问为什么用list.add添加会有错？怎么改？错误提示是：构造函数 Person（String, int, String）未定义什么意思？

Answer 1

 public class People{
    private String name;
        private int age;
        private String city;
        public People(){
        }
        public People(String name,int age,String city){
         this.name=name;
        this.age=age;
        this.city=city;
        }
        public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
}