数组对象 增删改查

第一次博客

package com.bin.main;

import com.sun.org.apache.xpath.internal.objects.XString;

public class userinfo {
    user[] user = new user[30];//固定班级有30个学生

    static int a = 0;//当前学生数量

    /**
     * 添加 add
     */
    public void add(user u) {
        user[a] = u;
        a++;
    }

    /**
     * 查询所有
     */
    public void findAll() {
        for (int i = 0; i < a; i++) {
            System.out.println(user[i]);
        }
    }

    /**
     * 根据学号查询
     *
     * @param args
     */
    public void findByid(String id) {
        for (int i = 0; i < a; i++) {
            if (user[i].getId().equals(id)) {
                System.out.println(user[i]);
            }
        }

    }
/**
 * 修改
 */
public void update(user s){

    for (int i = 0; i < a; i++) {

        if (user[i].getId().equals(s.getId())) {
            user[i].setAge(s.getAge());
            user[i].setName(s.getName());

        }
    }
}

    /**
     * 删除
     *
     * @param args
     */
    public  void delete(String id) {
        int b = 0;//新数组下标
        user[] users = new user[user.length];//新数组
        for (int i = 0; i < a; i++) {
            if ( id != user[i].getId()) {
            users[b]=user[i];
            b++;

            }else {
            a--;

            }

        }
        user=users;
           a=b;

    }
        public static void main (String[]args){
            userinfo info = new userinfo();
            user u1 = new user("01", "张三", 20);
            info.add(u1);
            user u2 = new user("02", "李四", 22);
            info.add(u2);
            user u3 = new user("03", "lic", 28);
            info.add(u3);
            user u4 = new user("04", "aic", 28);
            info.add(u4);
          //  System.out.println("====================================");
          //  info.findAll();
          //  System.out.println("====================================");
         //   info.findByid("02");
            System.out.println("====================================");
          // info.delete("03");
         //   info.findAll();
            user u5 = new user("04", "abc", 28);

            info.update(u5);
            info.findAll();
        }
    }