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）

Collection

collection遍历方式

迭代遍历（不依赖索引）

增强for循环遍历

Lambda表达式遍历

List集合

---

List集合	添加的元素是有序、可重复、有索引的
Set集合	添加的元素无序、不重复、无索引

 ArraryList

• 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

• 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<Integer> 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<Student> 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 < num;i++){
                Student sd = new Student();
                System.out.print("请输入学生名字：");
                String name = sc.next();
                System.out.print("请输入学生年龄：");
                int age = sc.nextInt();
                sd.setName(name);
                sd.setAge(age);
                list.add(sd);
            }
            for (int i = 0; i < list.size(); i++){
                Student stu = list.get(i);
                System.out.println(stu.getName() + " " + stu.getAge());
            }
        }
    }
    

     

• 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<User> 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<User> list, String id){
            for (int i = 0; i < list.size(); i++){
                User u = list.get(i);
                String uid = u.getId();
                if (uid.equals(id)){
                    return true;
                }
            }
            return false;
        }
    }
    

• 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<Phone> 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<Phone> list){
            for (int i = 0; i < list.size(); i++){
                Phone phone = list.get(i);
                double price = phone.getPrice();
                if (price < 3000){
                    System.out.println(phone.getBrand() + phone.getPrice()) ;
                }
            }
        }
    }
    

• 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<Student> 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<Student> 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<Student> 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<Student> 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<Student> 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("id\t姓名\t年龄\t地址");
            for (int i = 0; i < list.size(); i++) {
                Student stu = list.get(i);
                System.out.println(stu.getId() + "\t" + stu.getName() + "\t" + stu.getAge() + "\t\t" + stu.getAddress());
            }
        }
    
    
        public static void forlist(ArrayList<Student> list) {
            for (int i = 0; i < list.size(); i++) {
                Student stu = list.get(i);
                System.out.println(stu.getId() + stu.getName() + stu.getAge() + stu.getAddress());
            }
        }
    
        public static boolean ifequals(ArrayList<Student> list, String id) {
            for (int i = 0; i < list.size(); i++) {
                Student stu = list.get(i);
                String id1 = stu.getId();
                if (id.equals(id1)) {
                    return true;
                }
            }
            return false;
        }
    
        //返回id的索引(findIdIndex)
        public static int idid(ArrayList<Student> list, String id) {
            for (int i = 0; i < list.size(); i++) {
                Student student = list.get(i);
                String id1 = student.getId();
                System.out.println(id1);
                if (id1.equals(id)) {
                    return i;
                }
            }
            return -1;
        }
    }
    

  • 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<User> 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<User> 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<User> 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<User> 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<User> list) {
            for (int i = 0; i < list.size(); i++) {
                User user = list.get(i);
                System.out.println(user.getUsername());
            }
        }
    
        //查询名称是否规范
        private static boolean checkUsername(String username) {
            //用户名长度在3-15
            int num = username.length();
            String name = "";
            int count = 0;
            if (num >= 3 && num <= 15) {
                //只能是字母+数字
                //纯字母可以
                for (int i = 0; i < num; i++) {
                    char c = username.charAt(i);
                    if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9') {
                        name = name + c;
                    } else {
                        return false;
                    }
                }
                for (int i = 0; i < num; i++) {
                    char c = name.charAt(i);
                    if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z') {
                        count++;
                    }
                }
                if (count == 0) {
                    return false;
                }
                ;
                return true;
            }
            return false;
    
        }
    
        //是否存在这个用户名
        private static boolean findUserByUsername(ArrayList<User> list, String username) {
    
            for (int i = 0; i < list.size(); i++) {
                User user1 = list.get(i);
                String username1 = user1.getUsername();
                if (username.equals(username1)){
                    return true;
                }
            }
            return false;
        }
    
        //返回用户名的index
        public static String userIdIndex(ArrayList<User> list,String username){
            String a = "用户名不存在";
            for (int i = 0; i < list.size(); i++) {
                User user = list.get(i);
                String username1 = user.getUsername();
                if (username.equals(username1)){
                    String password = user.getPassword();
                    return password;
                }
            }
            return a;
        }
    
        //查看密码是否匹配
        private static boolean checkPassword(ArrayList<User> list, String username, String password) {
            for (int i = 0; i < list.size() ; i++) {
                boolean eq = list.get(i).getUsername().equals(username);
                if (eq){
                    String password1 = list.get(i).getPassword();
                    if (password.equals(password1)){
                        return true;
                    }
                }
            }
            return false;
        }
    
        //两次密码是否一致
        private static boolean checkTwoPassword(String password, String newpassword) {
            if (password.equals(newpassword)){
                return true;
            }
            return false;
        }
    
    }
    

Collection

• collection的功能是全部单列集合都可以继承使用的（接口）
  

• collection遍历方式

  • 迭代遍历（不依赖索引）

    • 图示
      
      循环结束后 指针不会复位

  • 增强for循环遍历

    • 用处
      • 所有的单链集合
      • 数组
    • 用法
      

  • Lambda表达式遍历

    • 利用匿名内部类
    • 原理：遍历集合，得到每一个元素，传递给accept方法
      

• List集合

  • list是是接口
  • 方法

    add()	在集合指定位置插入集合的元素
    remove()	按索引删除
    set()	修改索引处元素
    get()	返回索引处元素

  • 使用
    
  • list循环遍历的五种方式
    • 迭代器
    • 列表迭代器
    • 增强for循环
    • Lambda表达式
    • 普通for循环

• Linkedlist

  • 方法