Java---ArrayList的增删改查代码

一、创建插入元素类

import java.util.Objects;

/**
 * @author created  by jackie on 2020/4/23
 * @description:
 */

public class UserInfo {
    private String userName;
    private String city;

    public UserInfo(String userName, String city) {
        this.userName = userName;
        this.city = city;
    }


    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    @Override
    public String toString() {
        return "UserInfo{" +
                "userName='" + userName + '\'' +
                ", city='" + city + '\'' +
                '}';
    }
}

二、arrayListdemo代码

import java.util.ArrayList;

/**
 * @author created  by jackie on 2020/4/23
 * @description:
 */

public class ArrayListDemo {

    /**
        * @description: ArrayList普通元素增删查
        * @author created by jackie on  2020/4/23
        */
    @Test
    public void ArrayListTest(){
        ArrayList list = new ArrayList();
        list.add("jackie");
        list.add("lily");
        list.add("ben"); //添加字符串元素
        list.remove(0); //删除元素

        for (int i = 0; i <list.size(); i++) {
            System.out.println(list.get(i));
        }
    }


    /**
        * @description: ArrayList对自定义对象增的删改查
        * @author created by jackie on  2020/4/23
        */
    @Test
    public void ArrayListTest2(){

        //创建UserInfo对象，输入信息
        UserInfo userInfo1 = new UserInfo("jackie","GuangZhou");
        UserInfo userInfo2 = new UserInfo("Ben","Shenzhen");
        UserInfo userInfo3 = new UserInfo("lily","Shanghai");

        //向Arraylist添加对象
        ArrayList userList = new ArrayList();
        userList.add(userInfo1);
        userList.add(userInfo2);
        userList.add(userInfo3);


        //在指定位置添加一个对象
        UserInfo userInfo4 = new UserInfo("homer","BeiJing");
        userList.add(0,userInfo4); //数值0代表arraylist索引，0为最前面。在最开头插入一个对象

        //删除指定对象
        userList.remove(userInfo4);

        //删除指定索引的对象
        userList.remove(2);

        //设置对象的属性值
        userInfo1.setUserName("Jackie_2");
        userList.set(0,userInfo1);

        //遍历元素
        for (int i = 0; i <userList.size() ; i++) {
            System.out.println(((UserInfo)(userList.get(i))).getUserName()+"  "+((UserInfo)(userList.get(i))).getCity());
            //arraylist 的get()返回的是Object对象，所以要强制转换成UserInfo对象
        }


    }

}