package com.itheima.string; import java.util.Random; public class StringExec8 { public static void main(String[] args) { //1.定义出现的字符信息 String datas = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; //2.循环5次,每次生成一个随机的索引,提取对应的字符连接起来即可 String code = ""; Random r = new Random(); for (int i = 0; i < 5; i++) { //随机一个索引 int index = r.nextInt(datas.length()); char c = datas.charAt(index); code += c; } //3.输出字符串变量即可 System.out.println(code); } }
package com.itheima.string; import java.util.Scanner; public class StringExec7 { public static void main(String[] args) { //1.定义正确的登录名称和密码 String okLoginName = "admin"; String okPassword = "itheima" ; //2.定义一个循环,循环3次,让用户登录 Scanner sc = new Scanner(System.in); for (int i = 0; i <= 3 ; i++) { System.out.println("请您输入登录名称:"); String loginName = sc.next(); System.out.println("请您输入登录密码:"); String password = sc.next(); //3.判断登录是否成功 if(okLoginName.equals(loginName)){ //4.判断密码是否正确 if(okPassword.equals(password)){ System.out.println("登录成功!欢迎进入系统随意浏览~~~"); break; }else{ // 密码错误了 System.out.println("您的密码不正确!您还剩余" + (3 - i) + "次机会登录!"); } }else{ System.out.println("您的登录名称不正确!您还剩余" + (3 - i) + "次机会登录!"); } } } }
package com.itheima.string; import java.util.Scanner; public class StringExce8 { public static void main(String[] args) { //1.键盘录入一个手机号码 Scanner sc = new Scanner(System.in); System.out.println("请您输入您的手机号码:"); String tel = sc.next(); //2.截取号码的前三位,后四位 18665666520 String before = tel.substring(0,3); // 0 1 2 String after = tel.substring(7); // 从索引7开始截取到手机号码的末尾 String s = before + "****" + after; System.out.println(s); } }
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