Poj Solution 3157

http://poj.org/problem?id=3157

 import java.util.*;  
   
 public class Main {  
   
     public static void main(String[] args) {  
         Scanner cin = new Scanner(System.in);  
           
         while(cin.hasNext())  
         {  
             String str = cin.nextLine();  
       
             int type = checkType(str);  
             if(type == -1)  
                 System.out.println("Error!");  
             else if(type == 1)  
             {  
                 StringBuffer sb = new StringBuffer();  
                 while(str.indexOf("_") != -1)  
                 {  
                     int index = str.indexOf("_");  
                     sb.append(str.substring(0, index));  
                     if(index != 0)  
                     {  
                         String tmp = str.substring(index+1);  
                         str = FUpper(tmp);  
                     }else  
                         str = str.substring(index+1);  
                       
                 }  
                 sb.append(str);  
                 System.out.println(sb.toString());  
             }  
             else if(type == 2)  
             {  
                 StringBuffer sb = new StringBuffer();  
                 for(int i = 0; i < str.length(); i++)  
                 {  
                     char c = str.charAt(i);  
                     if(c >= 97 && c <= 122)  
                     {  
                         sb.append(c);  
                     }else if(c >= 65 && c <= 90)  
                     {  
                         sb.append('_');  
                         sb.append((char)(c+32));  
                     }  
                 }  
                 System.out.println(sb.toString());  
             }  
                   
         }  
   
     }  
       
     private static String FUpper(String str)  
     {  
         StringBuffer sb = new StringBuffer();  
           
         sb.append((char)(str.charAt(0) - 32));  
         if(str.length() > 1)  
             sb.append(str.substring(1));  
         return sb.toString();  
     }  
       
     private static int checkType(String str)  
     {  
         if(str.endsWith("_"))  
             return -1;  
         if(str.startsWith("_"))  
             return -1;  
           
         if(str.indexOf("_") != -1)  
         {             
             for(int i = 0; i < str.length(); i++)  
             {  
                 if((str.charAt(i) + 0) >= 65 && (str.charAt(i) + 0) <= 90)  
                     return -1;  
                 if(str.charAt(i) == '_' && i != 0 && i != str.length()-1)  
                     if(str.charAt(i-1) == '_' || str.charAt(i+1) == '_')  
                         return -1;  
             }  
               
             return 1;  
         }  
       
         if(str.charAt(0) >= 65 && str.charAt(0) <= 90)  
             return -1;  
   
         return 2;  
     }  

}