JavaSE练习

给定一个大小为 n 的数组 nums ，返回其中的多数元素。
多数元素是指在数组中出现次数 大于 n/2 的元素。

arr = {1, 2, 1, 1, 2, 2, 1, 3, 1, 1};

public class Demo01 {
    public static void main(String[] args) {
        int[] arr = {1, 2, 1, 1, 2, 2, 1, 3, 1, 1};
        Arrays.sort(arr);
        if (arr.length >= 3) {
            int num = arr[arr.length / 2];
            System.out.println("该数组的多数元素为:" + num);
        } else {
            System.out.println("没有多数元素");
        }
    }
}

综合案例（用户博客管理系统）：

package org.oracle.system;
//用户属性
public class User{
    private int id;
    private String userName;
    private String password;
    private int age;
    private String gender;

    public int getId() {
        return id;
    }

    public void setId(int 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;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public User() {
    }

    public User(int id, String userName, String password, int age, String gender) {
        this.id = id;
        this.userName = userName;
        this.password = password;
        this.age = age;
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                ", gender='" + gender + '\'' + '}';
    }
}

package org.oracle.system;

import java.util.Date;
//文章属性
public class Article {
    private String title;
    private String content;
    private User user;
    private Date publishTime;
    private Date modifyTime;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public User getAuthor() {
        return user;
    }

    public void setAuthor(User user) {
        this.user = user;
    }

    public Date getPublishTime() {
        return publishTime;
    }

    public void setPublishTime(Date publishTime) {
        this.publishTime = publishTime;
    }

    public Date getModifyTime() {
        return modifyTime;
    }

    public void setModifyTime(Date modifyTime) {
        this.modifyTime = modifyTime;
    }

    public Article() {

    }

    public Article(User user){
        this.user = user;
    }

    public Article(String title, String content, User user, Date publishTime) {
        super();
        this.title = title;
        this.content = content;
        this.user = user;
        this.publishTime = publishTime;
    }

    public Article(String title, String content, User user, Date publishTime, Date modifyTime) {
        super();
        this.title = title;
        this.content = content;
        this.user = user;
        this.publishTime = publishTime;
        this.modifyTime = modifyTime;
    }

    @Override
    public String toString() {
        return "Article [title=" + title + ", content=" + content + ", author=" + user + ", publishTime="
                + publishTime + ", modifyTime=" + modifyTime + "]";
    }
}

package org.oracle.system;

import java.util.ArrayList;
import java.util.Scanner;
//用户注册
public class Register {
    private User user;
    static ArrayList<User> arrayList = new ArrayList<>();
    private Scanner sc = new Scanner(System.in);

    public void add(User user){
        arrayList.add(user);
    }

    public ArrayList<User> findAll() {
        return arrayList;
    }

    public User findById(int id) {
        User us = null;
        for (User u : arrayList) {
            if (u.getId() == id) {
                us = u;
                break;
            }
        }
        return us;
    }
}
package org.oracle.system;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.Scanner;
//文章操作
public class ArticleActions {
    private User user;
    static ArrayList<Article> list = new ArrayList<>();
    Scanner sc = new Scanner(System.in);

    public ArticleActions(User user){
        this.user = user;
    }

    //写文章
    public void write() {
        System.out.println("请输入标题:");
        String title = sc.next();
        if (isExists(title)){
            System.out.println("已存在该文章，请重新输入!!");
            write();
        }else {
            System.out.println("请输入内容:");
            String content = sc.next();
            if (!content.equals("")){
                System.out.print("发布时间为:");
                Date publishTime = new Date();
                SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
                System.out.println(formatter.format(publishTime));
                Article article = new Article(title, content, user, publishTime);
                list.add(article);
                display(title);
            }
        }
    }
    //修改文章
    public void revise() {
        System.out.println("请输入您要修改的文章标题:");
        String title = sc.next();
        if (isExists(title)){
            for (Article article : list) {
                if (title.equals(article.getTitle())) {
                    System.out.println("请输入修改后的标题:");
                    article.setTitle(sc.next());
                    System.out.println("请修改内容:");
                    article.setContent(sc.next());
                    System.out.print("修改时间为:");
                    Date modifyTime = new Date();
                    SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
                    System.out.println(formatter.format(modifyTime));
                    article.setModifyTime(modifyTime);
                    display(article.getTitle());
                }
            }

        }else {
            System.out.println("不存在该文章，请重新输入标题");
            revise();
        }
    }
    //删除文章
    public void removeArticle(){
        System.out.println("请输入您要删除的文章的标题:");
        String title = sc.next();
        if (isExists(title)){
            for (Article article : list) {
                if (title.equals(article.getTitle())) {
                    if (list.remove(article)){
                        System.out.println("删除成功!!!");
                        break;
                    }else {
                        System.out.println("删除失败!!!");
                        break;
                    }
                }
            }
        }else {
            System.out.println("不存在该文章，请重新输入标题");
            removeArticle();
        }
    }

    //查看文章
    public void checkArticle(){
        if (!list.isEmpty()){
            for (Article article : list){
                System.out.println(article);
            }
        }else {
            System.out.println("您还没有写过文章！");
        }

    }

    //是否存在文章
    public boolean isExists(String name) {
        int n = 0;
        for (Article article : list) {
            if (name.equals(article.getTitle())) {
                n++;
            }
        }
        if (n != 0) {
            return true;
        }
        return false;
    }

    //展示文章
    public void display(String title){
        if (isExists(title)){
            for (Article article : list) {
                if (title.equals(article.getTitle())) {
                    System.out.println("标题:" + title);
                    System.out.println("作者:" + article.getAuthor().getUserName());
                    System.out.println("内容:" + article.getContent());
                    SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
                    System.out.println("发布时间:" + formatter.format(article.getPublishTime()));
                    if (article.getModifyTime() != null){
                        System.out.println("修改时间:" + formatter.format(article.getModifyTime()));
                    }else {
                        System.out.println("修改时间:" + null);
                    }

                }
            }
        }else {
            System.out.println("不存在该文章");
        }
    }
}
package org.oracle.system;

import java.util.Scanner;

import static org.oracle.system.Register.arrayList;
//测试
public class Test {
    static Scanner sc = new Scanner(System.in);

    public static void main(String[] args){
        boolean b = true;
        while (b){
            System.out.println("请选择1(注册)、2(登录)、3(退出):");
            int choice = sc.nextInt();
            switch (choice){
                case 1:
                    register();
                    break;
                case 2:
                    login();
                    break;
                case 3:
                    System.out.println("退出");
                    b = false;
                    break;
                default:
                    System.out.println("请重新选择！！！");
            }
        }
    }
    //注册
    public static void register(){
        Register register = new Register();
        System.out.println("---注册---");
        System.out.println("请输入姓名:");
        String userName = sc.next();
        if (isExists(userName)){
            System.out.println("已存在该用户,请重新输入信息!!");
            register();
        }else {
            System.out.println("请输入id:");
            int userId = sc.nextInt();
            System.out.println("请输入密码:");
            String password = sc.next();
            System.out.println("请输入年龄:");
            int age = sc.nextInt();
            System.out.println("请输入性别:");
            String gender = sc.next();
            User user = new User(userId, userName, password, age, gender);
            System.out.println("注册成功!!");
            register.add(user);
        }



    }
    //登录
    public static void login(){
        System.out.println("---登录---");
        System.out.println("请输入用户名：");
        String name = sc.next();
        if (isExists(name) && !arrayList.isEmpty()){
            System.out.println("请输入密码：");
            String pwd = sc.next();
            for (User u : arrayList) {
                if (name.equals(u.getUserName()) && pwd.equals(u.getPassword())) {
                    System.out.println("登录成功!!");
                    articleView(u);
                    break;
                }else {
                    System.out.println("登陆失败，请重新登录!!");
                    login();
                }
            }
        }else {
            System.out.println("用户不存在，请重新登录!!");
            login();
        }
    }

    //是否存在用户
    public static boolean isExists(String name) {
        int n = 0;
        for (User u : arrayList) {
            if (name.equals(u.getUserName())) {
                n++;
            }
        }
        if (n != 0) {
            return true;
        }
        return false;
    }

    //文章界面
    public static void articleView(User user){
        Article article = new Article(user);
        ArticleActions aa = new ArticleActions(user);
        System.out.println("欢迎进入博客!!!");
        boolean b = true;
        while(b){
            System.out.println("1 : 写文章");
            System.out.println("2 : 修改文章");
            System.out.println("3 : 删除文章");
            System.out.println("4 : 查看文章");
            System.out.println("5 : 退出");
            System.out.println("请输入序号:");
            int num = sc.nextInt();
            switch (num){
                case 1:
                    aa.write();
                    break;
                case 2:
                    aa.revise();
                    break;
                case 3:
                    aa.removeArticle();
                    break;
                case 4:
                    aa.checkArticle();
                    break;
                case 5:
                    System.out.println("退出");
                    b = false;
                    break;
                default:
                    System.out.println("请输入1~5的序号!!");
                    articleView(user);
            }

        }
    }

}

Team8（抽象类）
定义一个抽象的"Role"类 有姓名 年龄 性别等成员变量
1. 要求尽可能隐藏所有变量(能够私有就私有,能够保护就不要公有)
再通过GetXXX()和SetXXX()方法对各变量进行读写。具有一个抽象的play()方法
该方法不返回任何值 同时至少定义两个构造方法。Role类中要体现出this的几种用法。
2. 从Role类派生出一个"Employee"类 该类具有Role类的所有成员
构造方法除外 并扩展 salary成员变量 同时增加一个静态成员变量“职工编号 ID ”。
同样要有至少两个构造方法 要体现出this和super的几种用法
还要求覆盖play()方法 并提供一个final sing()方法。
3. “Manager"类继承"Employee"类 有一个final成员变量"vehicle”
4. 在main()方法中制造Manager和Employee对象,并测试这些对象的方法

public class Test01 {
    public static void main(String[] args) {
        Employee employee = new Employee("张三", 33, "男", 10001);
        employee.setSalary(5000);
        employee.play();
        employee.sing();

        Manager manager = new Manager("李四", 25, "男", 10002, 8000.0);
        manager.play();
        System.out.println("我有一辆" + manager.getVEHICLE());

    }
}

Team9（抽象类）
品尝饮料
1、建立一个Java抽象类Drink 应当
a、声明一个抽象方法taste() 该方法负责输出饮料的味道
b、声明int型常量来代表不同的饮料类型 如：咖啡、啤酒、牛奶
c、声明静态工厂方法getDrink(int drinkType) 根据传入的参数创建不同的饮料对象 并返回该对象 建议使用switch语句。该方法要求声明DrinkNotFoundException 当没有相对应的饮料类型时 抛出该异常。
2、建立Drink的具体子类
a、分别建立Drink的子类 Coffee 代表咖啡 Beer 代表啤酒 Milk 代表牛奶 ; b、实现taste()方法 要求在控制台打印各自的味道特征。
3、建立异常类DrinkNotFoundException
a、继承Exception
b、在Drink的 方 法getDrink(int drinkType)中 声 明 引 发DrinkNotFoundException异常 当传入的参数没有相对应的饮料类型时 抛出异常。
c、在使用getDrink方法的类中捕捉该异常。
4、建立Test测试类 测试以上内容的正确性
a、编写main方法 通过命令行传参的方式传入某种饮料的类型。
b、在main方法中 调用Drink类的getDrink方法 获得相应的饮料对象。注意捕获DrinkNotFoundException。
c、然后调用该饮料对象的taste()方法 输出该饮料的味道。
5、编译程序 并运行。
注意事项 1、仔细审题 把题目要求理解准确 2、请注意多态性的运用 3、请注意代码的书写、命名符合规范 应有适当的注释

public abstract class Drink {

    int Coffee, Beer, Milk;

    public abstract void taste();

    public static int getDrink(int drinkType) throws DrinkNotFoundException {
        switch (drinkType){
            case 1:
                System.out.println("咖啡:");
                Coffee coffee = new Coffee();
                coffee.taste();
                break;
            case 2:
                System.out.println("啤酒");
                Beer beer = new Beer();
                beer.taste();
                break;
            case 3:
                System.out.println("牛奶");
                Milk milk = new Milk();
                milk.taste();
                break;
            default:
                throw new DrinkNotFoundException();
        }
        return drinkType;
    }
}
public class Coffee extends Drink{
    @Override
    public void taste() {
        System.out.println("苦的");
    }
}

public class Beer extends Drink{
    @Override
    public void taste() {
        System.out.println("一股酒味儿");
    }
}

public class Milk extends Drink{
    @Override
    public void taste() {
        System.out.println("奶香味");
    }
}
public class DrinkNotFoundException extends Exception{
    private static final long serialVersionUID = 1L;
}

import java.util.Scanner;

public class Test02 {
    public static void main(String[] args) throws DrinkNotFoundException{
        Scanner sc =new Scanner(System.in);
        System.out.println("请输入1(咖啡)，2(啤酒)，3(牛奶):");
        try {
            int num = sc.nextInt();
            Drink.getDrink(num);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}