Java小练习

1.模拟一个微信抢红包的算法：

package study;

import java.util.Random;
import java.util.Scanner;

public class RedBags {
    public static void main(String[] args){
        System.out.println("====微信抢红包模拟器！！====");
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入红包的金额：");
        double money = scanner.nextDouble();
        System.out.println("请输入红包个数：");
        int num = scanner.nextInt();
        double minmoney = 0.01;
        Random random = new Random();
        if (money / num == 0.01){
            for (int i = 1; i <= num; i++){
                System.out.printf("第%d个红包的金额是%.2f%n", i, minmoney);
            }
        }else if (money / num < 0.01){
            System.out.println("不好意思红包最小金额必须是0.01，您的分配比例有问题！！");
        }else {
            for (int j = 1; j < num; j++){
                double maxmoney = money - (num - j) * 0.01;
                double qj = maxmoney - minmoney;
                double save = (double) random.nextInt((int)(qj * 100))/100;
                double zhmoney = save + minmoney;
                money = money - zhmoney;
                System.out.printf("第%d个红包的金额是%.2f%n", j, zhmoney);

            }
        }
        System.out.printf("第%d个红包的金额是%.2f%n", num, money);
    }
}

2.模拟一个彩票随机号：

package practise;

import java.util.Random;

public class Test6 {
    public static void main(String[]  args){
        Random random = new Random();
        int[] nums = new int[7];
        for (int i = 0; i < 5; i++){
            int num = random.nextInt(35);
            nums[i] = num;
            for (int j = 0; j < i; j++){
                if (nums[i] == nums[j]){
                    i--;
                    break;
                }
            }
        }
        for (int i = 5; i < 7; i++){
            int num = random.nextInt(10);
            nums[i] = num;
            if (nums[5] == nums[6]){
                i--;
            }
        }
        for (int i = 0; i <= nums.length - 1; i++){
            System.out.print(nums[i] + ",");
        }

    }
}

3.java一个简单的控制台程序

package 图形计算器;

import java.util.Scanner;

public class Count {
    public static boolean kz = true;
    public static void main(String[] args){
        while(kz) {
            System.out.println("======图形计算器======");
            System.out.println("====a-三角形");
            System.out.println("====b-矩形");
            System.out.println("====c-圆形");
            System.out.println("====d-任意四边形");
            System.out.println("====e退出");
            System.out.println("请输入你要选择的图形的编号");
            Scanner scanner = new Scanner(System.in);
            String st = scanner.next();
            select(st);
        }
    }
    public static void select(String st){
        switch (st){
            case "a":
                Triangle triangle = new Triangle();
                triangle.area();
                triangle.perimeter();
                break;
            case "b":
                Rectangle rectangle = new Rectangle();
                rectangle.area();
                rectangle.perimeter();
                break;
            case "c":
                Round round = new Round();
                round.area();
                round.perimeter();
                break;
            case "d":
                System.out.println("还在建设");
                break;
            case "e":
                kz = false;
                System.out.println("欢迎下次在来");
                break;
        }
    }
}


class Triangle{
    private final double a;
    private final double b;
    private final double c;
    public Triangle(){
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入三角形边长a:");
        double a = scanner.nextDouble();
        System.out.print("请输入三角形边长b:");
        double b = scanner.nextDouble();
        System.out.print("请输入三角形边长c:");
        double c = scanner.nextDouble();
        this.a = a;
        this.b = b;
        this.c = c;
        Verifier(a, b, c);
    }
    private static void Verifier(double a, double b, double c){  // 验证器
        if (a + b < c || a + c < b || b + c < a || a <= 0 || b <= 0 || c <= 0){
            System.out.println("请重新输入，你输入的根本不是三角形！！！请检查！！");
            new Triangle();
        }
    }
    void area(){
        double s = (a + b + c)/2;
        double mj = Math.sqrt(s*(s-a)*(s-b)*(s-c));
        System.out.printf("三角形的面积是： %.2f %n", mj);
    }
    void perimeter(){
        double l = a + b + c;
        System.out.printf("三角形的面积是： %.2f%n", l);
    }
}

class Rectangle{
    private final double a;
    private final double b;
    public Rectangle(){
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入矩形边长a:");
        double a = scanner.nextDouble();
        System.out.print("请输入矩形边长b:");
        double b = scanner.nextDouble();
        this.a = a;
        this.b = b;
        Verifier(a, b);
    }
    private static void Verifier(double a, double b){
        if ( a <= 0 || b <= 0){
            System.out.println("请输入一个正常的矩形边长必须大于0");
            new Rectangle();
        }
    }
    void area(){
        double mj = a * b;
        System.out.printf("矩形的面积是： %.2f %n", mj);
    }
    void perimeter(){
        double l = (a + b) * 2;
        System.out.printf("矩形的周长是： %.2f %n", l);
    }
}

class Round{
    private final double r;
    public Round(){
        System.out.print("请输入圆的半径");
        Scanner scanner = new Scanner(System.in);
        double r = scanner.nextDouble();
        this.r = r;
        Verifier(r);
    }
    private static void Verifier(double r){
        if (r <= 0){
            System.out.println("请输入一个正常的圆，半径不能低于0");
            new Round();
        }
    }
    void area(){
        double mj = Math.PI * r * r;
        System.out.printf("圆的面积是： %.2f %n", mj);
    }
    void perimeter(){
        double l = Math.PI * 2 * r;
        System.out.printf("圆的周长是； %.2f %n", l);
    }
}

基于java读写操作写的一个用户信息管理系统代码如下：

package 身份信息入库系统;

import java.io.*;
import java.util.Arrays;
import java.util.Scanner;

public class Test {
    public static boolean kz = true;
    public static void main(String[] args) throws IOException {
        while (kz){
            System.out.println("======身份信息入库系统======");
            System.out.println("1-注册");
            System.out.println("2-登入");
            System.out.println("3-打印所有信息");
            System.out.println("4-退出");
            System.out.println("请输入你要选择的编号");
            Scanner scanner = new Scanner(System.in);
            int num = scanner.nextInt();
            select(num);
        }

    }
    public static void select(int num) throws IOException {
        switch (num){
            case 1:
                Post post = new Post();
                post.write();
                break;
            case 2:
                System.out.println("请输入您的姓名");
                Scanner scanner = new Scanner(System.in);
                String name = scanner.next();
                System.out.println("请输入您的密码");
                int password = scanner.nextInt();
                Login login = new Login(name, password);
                break;
            case 3:
                Show show = new Show();
                break;
            case 4:
                System.out.println("欢迎下次再来！");
                kz = false;
                break;
        }
    }
}

interface Validtor{
    boolean validtor(String name, int password) throws IOException;
}

class ReadWrite{


    ReadWrite() throws IOException {
    }

    static File file() throws IOException {
        File file = new File("src/身份信息入库系统/test.txt");
        if (!file.exists()){
            file.createNewFile();
        }
        return file;
    }
    FileReader f = new FileReader(file());
    BufferedReader fr = new BufferedReader(f);

    public void write(String s) throws IOException {
        FileWriter fw = new FileWriter(file(), true);
        fw.write(s);
        fw.flush();
        fw.close();
    }

    public BufferedReader read() throws IOException {
        return fr;
    }
}

class Login implements Validtor{
    private String name;
    private int password;
    public Login(String name, int password) throws IOException {
        this.name = name;
        this.password = password;
        if (validtor(name, password)){
            System.out.println("该用户不存在！请重新输入！");
        }else {
            System.out.println("登入成功！！");
        }

    }

    @Override
    public boolean validtor(String name, int password) throws IOException {
        ReadWrite readWrite = new ReadWrite();
        String query = null;
        while ((query = readWrite.read().readLine()) != null ){
            String[] query2 = query.split("-", 3);
            if (query2[0].equals(name)){
                return false;
            }
        }
        return true;
    }
}

class Post implements Validtor{
    private final String name;
    private final int password;
    private final double hight;
    private final double weight;
    private final String aboutme;
    public Post(){
        System.out.println("请输入您的姓名：");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.next();
        System.out.println("请输入你的密码 ：");
        int password = scanner.nextInt();
        System.out.println("请输入你的身高 ：");
        double hight = scanner.nextDouble();
        System.out.println("请输入你的体重 ：");
        double weight = scanner.nextDouble();
        System.out.println("请输入你的个人介绍 ：");
        String aboutme = scanner.next();
        this.name = name;
        this.password = password;
        this.hight = hight;
        this.weight = weight;
        this.aboutme = aboutme;

    }
    void write() throws IOException {
        if (validtor(name, 1)){
            ReadWrite readWrite = new ReadWrite();
            String s = name + "-" + password + "-" + hight + "-" + weight + "-" + aboutme + "\r\n";
            readWrite.write(s);
        }else {
            System.out.println("该用户已经存在！！！");
            new Post();
        }
    }

    @Override
    public boolean validtor(String name, int password) throws IOException {
        ReadWrite readWrite = new ReadWrite();
        String query = null;
        while ((query = readWrite.read().readLine()) != null ){
            String[] query2 = query.split("-", 2);
            if (query2[0].equals(name)){
                return false;
            }
        }
        return true;
    }
}
class Show{
    public Show() throws IOException {
        ReadWrite readWrite = new ReadWrite();
        System.out.println("------------------------------");
        String query;
        while ((query = readWrite.read().readLine()) != null ){
            System.out.println(query);
        }
    }
}

JDBC操作：

package JDBC;

import java.sql.*;

public class Gradation {
    public Connection getConnection() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/java?serverTimezone=UTC&useSSL=false", "root", "196811");
        System.out.println("数据库连接成功");
        return con;
    }
    public static void main(String[] args) throws SQLException, ClassNotFoundException {
        Gradation conn = new Gradation();
        Connection con =null;
        Statement st = null;
        ResultSet rst = null;
        try{
            con = conn.getConnection();
            st = con.createStatement();
            rst = st.executeQuery("select * from test");
            while (rst.next()){
                String id = rst.getString("id");
                String name = rst.getString("name");
                String sex = rst.getString("sex");
                String age = rst.getString("age");
                System.out.println(id + "-" + name + "-" + sex + "-" + age);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (rst != null){
                rst.close();
            }
            if (st != null){
                st.close();
            }
            if (con != null){
                con.close();
            }
        }

    }
}