HWOJ将一个字符中所有出现的数字前后加上符号“*”，其他字符保

import java.util.Scanner;
public class Main{
public static void main(String[]args){
    Scanner s = new Scanner(System.in);
    String a = s.nextLine();
    StringBuffer sb = new StringBuffer();
    s.close();
    a="y"+a+"c";
    for(int i=0;i<a.length()-1;i++){
    if((!isNum(a.charAt(i))&&isNum(a.charAt(i+1)))||(isNum(a.charAt(i))&&!isNum(a.charAt(i+1)))){
    sb.append(a.charAt(i)).append("*");
    }else{
    sb.append(a.charAt(i));
    }
    }
    System.out.println(sb.substring(1));
}
    public static boolean isNum(char c){
    if(c>='0'&&c<='9'){
        return true;
    }else {
    return false;
    }
    }
}