Java零基础学习16：字符串练习

一、用户登录

package com.itheima;

import java.util.Scanner;

public class StringDemo4 {
    public static void main(String[] args) {
        String account1 = "123";
        String password1 = "123";
        // 提示用户输入账号和密码
        Scanner sc = new Scanner(System.in);
        // 定义计数器用于判断登录次数
        int count = 0;
        while (count < 3) {
            System.out.println("请输入账号");
            String account2 = sc.next();
            System.out.println("请输入密码");
            String password2 = sc.next();
            if (account1.equals(account2) && password1.equals(password2)) {
                System.out.println("登录成功");
                break;
            } else {
                count++;
                System.out.println("账号或密码错误！剩余：" + (3 - count) + "次机会");
            }
        }
        if(count>=3){
            System.out.println("登录失败");
        }
    }
}

二、遍历字符串

package com.itheima;

import java.util.Scanner;

public class StringDemo5 {
    public static void main(String[] args) {
        // 1. 键盘录入一个字符串
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个字符串");
        String str = sc.next();
        // 2. 进行遍历
        for (int i = 0; i < str.length(); i++) {
            // i 依次表示字符串的每一个索引
            char c = str.charAt(i);
            System.out.println(c);
        }
    }
}

三、统计字符次数

package com.itheima;

import java.util.Scanner;

public class StringDemo6 {
    public static void main(String[] args) {
        // 1. 键盘录入一个字符串
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个字符串");
        String str = sc.next();
        // 2. 统计：定义三个计数器
        int bigCount = 0;
        int smallCount = 0;
        int numberCount = 0;
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (c >= 'a' && c <= 'z') {
                smallCount++;
            } else if (c >= 'A' && c <= 'Z') {
                bigCount++;
            } else if (c >= '0' && c <= '9'){
                numberCount++;
            }
        }

        // 3. 输出打印
        System.out.println("小写字母有：" + smallCount + "个");
        System.out.println("大写字母有：" + bigCount + "个");
        System.out.println("数字有：" + numberCount + "个");
    }
}

四、金额转换

package com.itheima;

import java.util.Scanner;

public class StringDemo7 {
    public static void main(String[] args) {
        // 1.键盘录入一个金额
        Scanner sc = new Scanner(System.in);
        int money;
        while (true) {
            System.out.println("请录入一个金额");
            money = sc.nextInt();
            if (money >= 0 && money <= 9999999) {
                break;
            } else {
                System.out.println("金额无效");
            }
        }
        // 2.得到money中的每一位数字
        String moneyStr = "";
        while (true) {
            int ge = money % 10;
            String capitalNumber = getCapitalNumber(ge);
            moneyStr = capitalNumber + moneyStr;
            // 去掉刚刚获取的数据
            money = money / 10;

            if (money == 0) {
                break;
            }
        }
        // 3. 在前面补0，补齐7位
        int count = 7 - moneyStr.length();
        for (int i = 0; i < count; i++) {
            moneyStr = "零" + moneyStr;
        }

        // 4. 插入单位
        String[] arr = {"佰", "拾", "万", "千", "佰", "拾", "元"};
        for (int i = 0; i < moneyStr.length(); i++) {
            char c = moneyStr.charAt(i);
            System.out.print(c);
            System.out.print(arr[i]);
        }
    }

    public static String getCapitalNumber(int number) {
        // 定义数组
        String[] arr = {"零", "壹", "贰", "叁", "肆", "伍", "陆", "柒", "捌", "玖"};
        return arr[number];
    }
}