集合Arrary

Posted on by hackdl

目录

ArraryList

引用基本类型

案例1：定义一个集合添加学生姓名年龄

案例2：查看是否存在这个id

案例3：手机

案例4：学生管理系统（不完整）

  • 集合长度可变：自动扩容
  • 集合和数据
    长度 存储数据类型
    数组 长度固定 基本数据类型
    引用数据类型
    集合 长度可变 引用数据类型
    基本数据类型需变成包装类

ArraryList

  • 打印的是数据内容，不是地址值
  • 常用方法
    • 1.添加 add
    • 2.获取元素 get
    • 3.删除 remove
    • 4.修改 set
    • 5.查看长度 size

  • 引用基本类型

    • 需要用到包装类：ArrayList list1 = new ArrayList();
    • 包装类

  • 案例1：定义一个集合添加学生姓名年龄

    • Student类 
      package com.day1.day2;

public class Student {
    private String name;
    private int age;
    
    public Student() { }
    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    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; }

}
    • 测试类 
      package com.day1.day2;
import java.util.ArrayList;
import java.util.Scanner;

public class Test {
    public static void main(String[] args) {

        ArrayList list = new ArrayList();

        Scanner sc = new Scanner(System.in);

        System.out.print("请输入学生人数：");
        int num = sc.nextInt();

        for (int i = 0; i

       

  • 案例2：查看是否存在这个id

    • 需求：
      • main方法中定义一个集合，存入三个用户对象用户属性为:id，username，password，
      • 要求:定义一个方法，根据id查找对应的用户信息
        如果存在，返回true
        如果不存在，返回false
    • User类 
      package com.day1.day2;

public class User {
    private String id;
    private String username;
    private String password;

    public User(){}
    public User(String id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }
    public String getId() { return id; }
    public void setId(String id) { this.id = id; }
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getPassword() { return password; }
    public void setPassword(String password) { this.password = password; }
}

    • 测试类 
      package com.day1.day2;

import java.util.ArrayList;

public class Test2 {

    public static void main(String[] args) {
        
        ArrayList list = new ArrayList();
        User user1 = new User("001", "谢怜", "333");
        User user2 = new User("002", "花城", "666");
        User user3 = new User("003", "风师", "555555");

        list.add(user1);
        list.add(user2);
        list.add(user3);

        boolean contaions = contaions(list, "002");
        System.out.println(contaions);
    }

    public static boolean contaions(ArrayList list, String id){
        for (int i = 0; i

  • 案例3：手机

    • 需求：
      • 定义avabean类:PhonePhone属性:品牌，价格main方法中定义一个集合，存入三个手机对象。分别为:小米 2650  华为 5999 oppo 3569
      • 定义一个方法，将价格低于3000的手机信息返回
    • Phone类 
      package com.day1.day2;

import javax.crypto.spec.PSource;

public class Phone {
    private String brand;
    private double price;

    public Phone(){}
    public Phone(String brand, double price) {
        this.brand = brand;
        this.price = price;
    }

    public String getBrand() { return brand; }
    public void setBrand(String brand) { this.brand = brand; }
    public double getPrice() { return price; }
    public void setPrice(double price) { this.price = price; }
}
    • 测试类 
      package com.day1.day2;

import java.util.ArrayList;

public class Test3 {
    public static void main(String[] args) {
        ArrayList list = new ArrayList();
        Phone p1 = new Phone("小米", 2650);
        Phone p2 = new Phone("华为", 5999);
        Phone p3 = new Phone("oppo", 3569);

        list.add(p1);
        list.add(p2);
        list.add(p3);

        getPhoneInfo(list);
    }
    public static  void getPhoneInfo(ArrayList list){
        for (int i = 0; i

  • 案例4：学生管理系统（不完整）

    • Student类 
      package com.StudentGuanli;

public class Student {
    private String id;
    private String name;
    private int age;
    private String address;

    public Student(){}
    public Student(String id, String name, int age, String address) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public String getId() { return id; }
    public void setId(String id) { this.id = id; }
    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 getAddress() { return address; }
    public void setAddress(String address) { this.address = address; }
}
    • User类 
      package com.StudentGuanli;

public class User {
    private String username;
    private String password;
    private String personID;
    private String phoneNumber;

    public User(){ }
    public User(String username, String password, String personID, String phoneNumber) {
        this.username = username;
        this.password = password;
        this.personID = personID;
        this.phoneNumber = phoneNumber;
    }

    public String getUsername() { return username; }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getPersonID() {
        return personID;
    }
    public void setPersonID(String personID) {
        this.personID = personID;
    }
    public String getPhoneNumber() {
        return phoneNumber;
    }
    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }
}
    • 查询学生类 
      package com.StudentGuanli;

import java.util.ArrayList;
import java.util.Scanner;

public class StudentSystem {
    public static void startStudentSystem() {
        ArrayList list = new ArrayList();
        Student student1 = new Student("01", "谢怜", 600, "仙乐");
        list.add(student1);
        loop:
        while (true) {
            System.out.println("=======================欢迎来到学生管理系统==========================");
            System.out.println("1:添加学生");
            System.out.println("2：删除学生");
            System.out.println("3：修改学生");
            System.out.println("4：查询学生");
            System.out.println("5：退出");
            System.out.println("请输入您的选择");
            Scanner sc = new Scanner(System.in);
            String choose = sc.next();
            switch (choose) {
                case "1":
                    addStudent(list);
                    break;
                case "2": {
                    delectStudent(list);
                }
                break;
                case "3":
                    updataStudent(list);
                    break;
                case "4":
                    selectStudent(list);
                    break;
                case "5": {
                    System.out.println("退出");
                    break loop;
                }
            }
        }
    }

    public static void addStudent(ArrayList list) {
        System.out.println("====================添加学生=====================");
        Student stu = new Student();
        Scanner sc = new Scanner(System.in);
        String id;
        while (true) {
            System.out.print("添加学生id:");
            id = sc.next();
            boolean ifequals = ifequals(list, id);
            if (ifequals) {
                System.out.println("id存在 重新录入");
            } else {
                stu.setId(id);
                break;
            }
        }

        System.out.print("添加学生名字:");
        String name = sc.next();
        stu.setName(name);

        System.out.print("添加学生年龄:");
        int age = sc.nextInt();
        stu.setAge(age);

        System.out.print("添加学生地址:");
        String address = sc.next();
        stu.setAddress(address);

        list.add(stu);

        System.out.println("===学生信息添加成功===");
    }

    public static void delectStudent(ArrayList list) {
        System.out.println("====================删除学生====================");
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入学生学号：");
        String id = sc.next();
        boolean ifequals = ifequals(list, id);
        if (ifequals) {
            //查找uid的id索引
            int idid = idid(list, id);
            list.remove(idid);
            System.out.printf("========学号为%s的学生信息删除成功=======", id);
            System.out.println();
        } else {
            System.out.println("id不存在");
        }

    }

    public static void updataStudent(ArrayList list) {
        System.out.println("==========修改学生===============");
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入学生学号：");
        String id = sc.next();
//        boolean ifequals = ifequals(list, id);


//        if (ifequals==false){
//            System.out.println("输入的学号不存在");
//            return;
//        }
        int idid = idid(list, id);
        System.out.println(idid);
        if (idid == -1) {
            System.out.println("输入的学号不存在");
            return;
        }
        Student student = list.get(idid);   //需要修改的学生

        System.out.printf("修改%s学生的姓名：", id + "t");
        String newname = sc.next();
        student.setName(newname);

        System.out.printf("修改%s学生的年龄：", id + "t");
        int newage = sc.nextInt();
        student.setAge(newage);

        System.out.printf("修改%s学生的地址：", id + "t");
        String newaddress = sc.next();
        student.setAddress(newaddress);

        System.out.printf("====%s学生信息修改成功====", id);
    }

    public static void selectStudent(ArrayList list) {
        System.out.println("====================查询学生====================");
        if (list.size() == 0) {
            System.out.println("========没有学生数据=========");
            return;
        }
        System.out.println("idt姓名t年龄t地址");
        for (int i = 0; i  list) {
        for (int i = 0; i  list, String id) {
        for (int i = 0; i  list, String id) {
        for (int i = 0; i
    • 用户登录类 
      package com.StudentGuanli;

import java.util.ArrayList;
import java.util.Scanner;

public class App {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        User user = new User();
        ArrayList list = new ArrayList();

        loop:
        while (true) {

            System.out.println("===========欢迎来到学生管理系统登录界面===========");
            System.out.println("1：登录");
            System.out.println("2：注册");
            System.out.println("3：忘记密码");
            System.out.println("4：谢谢使用");
            System.out.println("5：查看用户");
            System.out.print("请选择操作：");
            int choose = sc.nextInt();
            System.out.println("=================================================");

            switch (choose) {
                case 1:
                    login(list);
                    break;
                case 2:
                    register(list);
                    break;
                case 3:
                    forgetPassword(list);
                    break;
                case 4:
                    System.out.println("4");
                    break loop;
                case 5:
                    lookUsername(list);
                    break;
                default:
                    System.out.println("没有这个选项");
            }
        }
    }

    private static void login(ArrayList list) {
        System.out.println("============登录============");
        User user = new User();
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入用户用户名：");
        String username = sc.next();
        System.out.print("输入密码：");
        String password = sc.next();
        //查看是否有这个用户名
        boolean userByUsername = findUserByUsername(list, username);
        if (userByUsername){

            //查看密码是否匹配
            boolean b = checkPassword(list, username, password);
            if (b){
                System.out.println("==============登录成功==============");
                StudentSystem studentSystem = new StudentSystem();
                studentSystem.startStudentSystem();
                return;
            }else {
                System.out.println("==============密码错误  登录失败==============");
            }
        }else {
            System.out.println("用户名不存在");
        }
    }


    private static void register(ArrayList list) {
        System.out.println("============注册============");
        User user = new User();
        Scanner sc = new Scanner(System.in);

        while (true) {
            System.out.print("请输入用户名：");
            String username = sc.next();
            boolean b = checkUsername(username);
            if (b) {
                user.setUsername(username);
                break;
            } else {
                System.out.println("用户名格式不规范，重新输入");
            }
        }

        while (true){
            System.out.print("请输入密码：");
            String password = sc.next();
            System.out.print("请重复输入密码：");
            String newpassword = sc.next();
            boolean b = checkTwoPassword(password, newpassword);
            if (b){
                user.setPassword(password);
                break;
            }else {
                System.out.println("==========两次密码不一致==========");
            }
        }

        System.out.print("请输入身份证号码：");
        String personID = sc.next();
        user.setPersonID(personID);

        System.out.print("请输入手机号码：");
        String phoneNumber = sc.next();
        user.setPhoneNumber(phoneNumber);

        list.add(user);

    }


    private static void forgetPassword(ArrayList list) {
        System.out.println("============忘记密码============");
        System.out.println("输入要查询的用户名");
        Scanner sc = new Scanner(System.in);
        String username = sc.next();
        String s = userIdIndex(list, username);
        System.out.printf("%s的密码是",username + s);
    }

    //查询用户名
    private static void lookUsername(ArrayList list) {
        for (int i = 0; i = 3 && num = 'a' && c = 'A' && c = '0' && c = 'a' && c = 'A' && c  list, String username) {

        for (int i = 0; i  list,String username){
        String a = "用户名不存在";
        for (int i = 0; i  list, String username, String password) {
        for (int i = 0; i

服务器托管，北京服务器托管，服务器租用 http://www.fwqtg.net

相关推荐: xlwings 将一个工作表的全部内容复制到另一个工作表 获取工作表的全部内容及行列数 写文章

xlwings 将一个工作表的全部内容复制到另一个工作表 https://github.com/xlwings/xlwings/pull/1216/files https://cloud.tencent.com/developer/ask/sof/868793…

服务器托管，北京服务器托管，服务器租用，机房机柜带宽租用

服务器托管

咨询：董先生

电话13051898268 QQ/微信93663045！

上一篇:
下一篇: