Java-黑马Java学习练习-day10字符串

学习视频链接：https://www.bilibili.com/video/BV17F411T7Ao

文章目录

练习1. 用户登录
练习2. 遍历字符串
练习3. 统计字符串次数
练习4. 字符串拼接
练习5. 字符串反转
练习6. 金额转换
练习7. 手机号屏蔽
练习8. 身份证信息查看
练习9. 敏感词替换
练习10. 对称字符串
练习11. 拼接字符串
练习12. 罗马数字
练习13. 调整字符串

练习1. 用户登录

已知用户名和密码，请用程序实现模拟用户登录。总共给三次机会，登录之后，给出相应的提示

package cn.kox.practice;import java.util.Scanner;/*** @ClassName: codePractice01* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习1，用户登录*/
public class codePractice01 {public static void main(String[] args) {String userName = "kox";String password = "Kox123";Scanner sc = new Scanner(System.in);int count = 3;while (count > 0) {System.out.print("输入用户名：");String user = sc.next();System.out.print("输入密码：");String pd = sc.next();if (user.equals(userName) && pd.equals(password)) {System.out.printf("欢迎%s, 登录成功！", user);System.out.println();break;} else {count--;System.out.printf("登录失败，还有%s次机会", count);System.out.println();}}}
}

练习2. 遍历字符串

键盘录入一个字符串，使用程序实现在控制台遍历该字符串

package cn.kox.practice;import java.util.Scanner;/*** @ClassName: codePractice02* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习2，遍历字符串*/
public class codePractice02 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);String str = sc.next();for (int i = 0; i < str.length(); i++) {System.out.println(str.charAt(i));}}
}

练习3. 统计字符串次数

键盘录入一个字符串，统计该字符串中大写字母字符，小写字母字符，数字字符出现的次数(不考虑其他字符)

package cn.kox.practice;import java.util.Scanner;/*** @ClassName: codePractice03* @Author: Kox* @Data: 2023/1/20* @Sketch: 统计字符次数*/
public class codePractice03 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.print("输入一个字符：");String str = sc.next();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 >= 48 && c <= 57) {numberCount++;}}System.out.printf("bigCount；%s, smallCount：%s, numberCount：%s", bigCount, smallCount, numberCount);}
}

练习4. 字符串拼接

定义一个方法，把 int 数组中的数据按照指定的格式拼接成一个字符串返回，调用该方法，

并在控制台输出结果。例如，数组为 int[] arr = {1,2,3}; ，执行方法后的输出结果为：[1, 2, 3]

package cn.kox.practice;/*** @ClassName: codePractice04* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习4，拼接字符串*/
public class codePractice04 {public static void main(String[] args) {int[] arr = {1, 2, 3 ,4};System.out.println(arrToString(arr));}public static String arrToString(int[] arr) {if (arr == null) {return "";}if (arr.length == 0) {return "[]";}String result = "[";for (int i = 0; i < arr.length; i++) {if (i == arr.length - 1) {result += arr[i] + "]";} else {result += arr[i] + ",";}}return result;}
}

练习5. 字符串反转

定义一个方法，实现字符串反转。键盘录入一个字符串，调用该方法后，在控制台输出结果

例如，键盘录入 abc，输出结果 cba

package cn.kox.practice;import java.util.Scanner;/*** @ClassName: codePractice05* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习5，字符串反转*/
public class codePractice05 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.print("输入一个字符串：");String str = sc.next();System.out.println(reversalString(str));}public static String reversalString(String str) {String result = "";for (int i = str.length()-1; i > -1; i--) {result += str.charAt(i);}return result;}
}

练习6. 金额转换

把2135变成：零佰零拾零万贰仟壹佰叁拾伍元

把789变成：零佰零拾零万零仟柒佰捌拾玖元

package cn.kox.practice;import java.util.Scanner;/*** @ClassName: codePractice06* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习6，金额转换*/
public class codePractice06 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int monkey;while (true) {System.out.print("请录入一个金额：");monkey = sc.nextInt();if (monkey >= 0 && monkey <= 9999999) {break;} else {System.out.println("金额无效");}}String moneyStr = "";while (true) {int ge = monkey % 10;String capitalNumber = getCapitalNumber(ge);moneyStr = capitalNumber + moneyStr;monkey = monkey / 10;if (monkey == 0) {break;}}int count = 7 - moneyStr.length();for (int i = 0; i < count; i++) {moneyStr = "零" + moneyStr;}System.out.println(moneyStr);String[] arr = {"佰", "拾", "万", "迁", "佰", "拾", "元"};String result = "";for (int i = 0; i < moneyStr.length(); i++) {char c = moneyStr.charAt(i);result = result + c + arr[i];}System.out.println(result);}public static String getCapitalNumber(int number) {String[] arr = {"零", "壹", "贰", "叁", "肆", "伍", "陆" , "柒", "捌", "玖"};return arr[number];}
}

练习7. 手机号屏蔽

需求：以字符串的形式从键盘接受一个手机号，将中间四位号码屏蔽

最终效果为：131****9468

package cn.kox.practice;/*** @ClassName: codePractice07* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习7，手机号屏蔽*/
public class codePractice07 {public static void main(String[] args) {String phoneNumber = "13112349468";String start = phoneNumber.substring(0, 3);String end = phoneNumber.substring(7, 11);phoneNumber = start + "****" + end;System.out.println(phoneNumber);}
}

练习8. 身份证信息查看

身份证的每一位都是有固定的含义：

1、2位：省份
3、4位：城市
5、6位：区县
7-14位：出生年、月、日
15、16位：所在地派出所
17位：性别（奇数男性，偶数女性）
18位：个人信息码（随机产生）

要求打印内容方式如下：

人物信息为：

出生年月日：XXXX年X月X日

性别为：男/女

package cn.kox.practice;/*** @ClassName: codePractice08* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习8，身份证信息查看*/
public class codePractice08 {public static void main(String[] args) {String id = "321281202001011234";// 获取出生年月日String year = id.substring(6, 10);String month = id.substring(10, 12);String day = id.substring(12, 14);System.out.println("人物信息为：");System.out.println("出生年月日：" + year + "年" + month + "月" + day + "日");char gender = id.charAt(16);int num = gender - 48;if (num % 2 == 0 ) {System.out.println("性别为：女");} else {System.out.println("性别为：男");}}
}

练习9. 敏感词替换

需求1：键盘录入一个字符串，如果字符串中包含（TMD），则使用***替换

package cn.kox.practice;/*** @ClassName: codePractice09* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习9，敏感词替换*/
public class codePractice09 {public static void main(String[] args) {String talk = "你玩的真好，以后不要再玩了，fuck";String[] arr = {"TMD", "CNM", "SB", "bitch", "fuck"};for (int i = 0; i < arr.length; i++) {talk = talk.replace(arr[i], "***");}System.out.println(talk);}
}

练习10. 对称字符串

需求：

键盘接受一个字符串，程序判断出该字符串是否是对称字符串，并在控制台打印是或不是

对称字符串：123321、111非对称字符串：123123

package cn.kox.practice;import java.util.Scanner;/*** @ClassName: codePractice10* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习10，对称字符串*/
public class codePractice10 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.print("请输入一个字符串：");String str = sc.next();String result = new StringBuilder().append(str).reverse().toString();System.out.println(str.equals(result));}
}

练习11. 拼接字符串

需求：定义一个方法，把 int 数组中的数据按照指定的格式拼接成一个字符串返回。

调用该方法，并在控制台输出结果。

例如：数组为int[] arr = {1,2,3};

执行方法后的输出结果为：[1, 2, 3]

package cn.kox.practice;/*** @ClassName: codePractice11* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习11，拼接字符串*/
public class codePractice11 {public static void main(String[] args) {int[] arr = {1, 2, 3};String result = arrToString(arr);System.out.println(result);}public static String arrToString(int[] arr) {StringBuilder sb = new StringBuilder();sb.append("[");for (int i = 0; i < arr.length; i++) {if (i == arr.length - 1) {sb.append(arr[i] + "]");} else {sb.append(arr[i]).append(", ");}}return sb.toString();}
}

练习12. 罗马数字

解法一

package cn.kox.practice;import java.util.Scanner;
import java.util.StringJoiner;/*** @ClassName: codePractice12* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习12，罗马数字*/
public class codePractice12Case1 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);String str;while (true) {System.out.println("请输入一个字符串");str = sc.next();boolean flag = checkStr(str);if (flag) {break;} else {System.out.println("输入错误！");}}StringJoiner sj = new StringJoiner(",", "[", "]");for (int i = 0; i < str.length(); i++) {char c = str.charAt(i);int number = c - 48;String s = changeLuoMa(number);sj.add(s);}System.out.println(sj);}public static String changeLuoMa(int number) {String[] arr = {"", "Ⅰ", "Ⅱ", "Ⅲ", "Ⅳ", "Ⅴ", "Ⅵ", "Ⅶ", "Ⅷ", "Ⅸ"};return  arr[number];}public static boolean checkStr(String str) {if (str.length() > 9) {return false;}for (int i = 0; i < str.length(); i++) {char c = str.charAt(i);if (c < '0' || c > '9') {return false;}}return true;}
}

解法二

package cn.kox.practice;import java.util.Scanner;
import java.util.StringJoiner;/*** @ClassName: codePractice12Case02* @Author: Kox* @Data: 2023/1/20* @Sketch:*/
public class codePractice12Case2 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);String str;while (true) {System.out.println("请输入一个字符串");str = sc.next();boolean flag = checkStr(str);if (flag) {break;} else {System.out.println("输入错误！");}}StringJoiner sj = new StringJoiner(",", "[", "]");for (int i = 0; i < str.length(); i++) {char c = str.charAt(i);String s = changeLuoMa(c);sj.add(s);}System.out.println(sj);}public static String changeLuoMa(char number) {String str =  switch (number) {case '1' -> "Ⅰ";case '2' -> "Ⅱ";case '3' -> "Ⅲ";case '4' -> "Ⅳ";case '5' -> "Ⅴ";case '6' -> "Ⅵ";case '7' -> "Ⅶ";case '8' -> "Ⅷ";case '9' -> "Ⅸ";default -> "";};return str;}public static boolean checkStr(String str) {if (str.length() > 9) {return false;}for (int i = 0; i < str.length(); i++) {char c = str.charAt(i);if (c < '0' || c > '9') {return false;}}return true;}
}

练习13. 调整字符串

解法一

package cn.kox.practice;/*** @ClassName: codePractice13* @Author: Kox* @Data: 2023/1/20* @Sketch: 练习13，调整字符串*/
public class codePractice13Case1 {public static void main(String[] args) {String strA = "abcde";String strB = "cdeabd";System.out.println(check(strA, strB));}public static boolean check(String strA, String strB) {for (int i = 0; i < strA.length(); i++) {strA = rotate(strA);if (strA.equals(strB)) {return true;}}return false;}// 旋转字符串，将左侧字符移动到右侧// 形参：旋转前的字符串// 返回值：旋转后的字符串public static String rotate(String str) {char first = str.charAt(0);String end = str.substring(1);return end + first;}
}

解法二

package cn.kox.practice;/*** @ClassName: codePracticeCase2* @Author: Kox* @Data: 2023/1/20* @Sketch:*/
public class codePractice13Case2 {public static void main(String[] args) {String strA = "abcde";String strB = "cdeab";System.out.println(check(strA, strB));}public static boolean check(String strA, String strB) {for (int i = 0; i < strA.length(); i++) {strA = rotate(strA);if (strA.equals(strB)) {return true;}}return false;}// 旋转字符串，将左侧字符移动到右侧// 形参：旋转前的字符串// 返回值：旋转后的字符串public static String rotate(String str) {char[] arr = str.toCharArray();char first = arr[0];for (int i = 1; i < arr.length; i++) {arr[i-1] = arr[i];}arr[arr.length-1] = first;String result = new String(arr);return result;}
}