键盘输入一个字符串：
1.长度小于等于九
2.只能是数字，将内容转换为罗马数字（0转换为"")
package example;import java.util.Scanner;public class demo04 {public static void main(String[] args) {//录入字符串Scanner sc = new Scanner(System.in);System.out.println("请输入一个合法的字符串：");String str = sc.nextLine();//字符串是否满足要求while (true) {if (check(str)) {System.out.println("字符串合法");break;} else {System.out.println("不合法，请重新输入：");str = sc.nextLine();}}//将内容变为罗马数字；1-Ⅰ，2-ⅡString[] result = new String[str.length()];for (int i = 0; i < str.length(); i++) {result[i]=changeLuoMa(str.charAt(i));}//讲结果打印出来for (int i = 0; i < result.length; i++) {System.out.print(result[i]);}}public static boolean check(String str) {if (str.length() > 9) {return false;}for (int i = 0; i < str.length(); i++) {if (str.charAt(i) <= '0' || str.charAt(i) >= '9') {return false;}}return true;}public static String changeLuoMa(char c) {String[] arr={"","I","Ⅱ","Ⅲ","Ⅳ","Ⅴ","Ⅵ","Ⅶ","Ⅷ","Ⅸ"};int num=c-48;return arr[num];}
}//利用ASCⅡ码将字符转化为数字
//'0'-0
