本文主要是介绍java字符串四道课后习题，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
import java.util.Scanner;public class uptolow_ {public static void main(String[] args) {// TODO 自动生成的方法存根System.out.println("请选择练习题:\n");Scanner lx = new Scanner(System.in);int lxt = lx.nextInt();if(lxt == 1)lx1();if(lxt == 2)lx2();if(lxt == 3)lx3();if(lxt == 4)lx4();}
//1.使用String类的toUpperCase()方法和toLowerCase()方法来实现大小写转换public static void lx1(){Scanner sc = new Scanner(System.in); System.out.println("请输入一个字符串：\n");String word = sc.nextLine();String Low_new_str = word.toLowerCase();String Up_new_str = word.toUpperCase();System.out.println(Low_new_str);System.out.println(Up_new_str);}
//2,分别截取str1和str2字符串中的部分内容，如果截取后的两个子串相同，输出相同public static void lx2(){Scanner sc2 = new Scanner(System.in);Scanner sc3 = new Scanner(System.in);System.out.println("请输入两个字符串\n");String word1 = sc2.nextLine();String word2 = sc3.nextLine();System.out.println("截取的起始位置:\n");Scanner start = new Scanner(System.in);int start_ = start.nextInt();System.out.println("截取的截止位置:\n");Scanner end = new Scanner(System.in);int end_ = end.nextInt();String substr1 = word1.substring(start_,end_);String substr2 = word2.substring(start_,end_);boolean result = substr1.equalsIgnoreCase(substr2);if(result == true){System.out.println("两个子串相同\n");}else{System.out.println("两个子串并不相同\n");}}//3,使用正则表达式来判断test是否为合法的手机号public static void lx3(){String regex = "\\p{Digit}{11}";//任意数字,正好出现13次Scanner phone_num = new Scanner(System.in);System.out.println("请输入一个字符串:\n");String test = phone_num.nextLine();if(test.matches(regex)){System.out.println("该手机号合法");}else{System.out.println("该手机号不合法\n");}}//4,使用字符串生成器,将字符串str追加1-10这10个数字public static void lx4(){StringBuilder str = new StringBuilder("该操作增加了1-10个数字:");str.insert(14, "1,2,3,4,5,6,7,8,9,10");System.out.println(str.toString());}
}
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