输入一个字符串，将字符串中的所有大写字母转换为小写字母，所有小写

import java.util.*;
public class Main {
   public static void main(String[] args) {
       // TODO code application logic here
       Scanner shuru=new Scanner(System.in);
       String shen = shuru.nextLine();
       shen = shen.replaceAll("[^a-zA-Z]","");
       char [] si = shen.toCharArray();
       for(int i = 0;i < si.length;i ++)
       {
           if((int)si[i]>=65 && (int)si[i]<=90)
           {
               si[i]+=32;
           }
           else
           {
               if((int)si[i]>=97 && (int)si[i]<=122)
               {
                   si[i]-=32;
               }
               else
               {
                   ;
               }
           }
       }
       for(int i = 0;i < si.length;i ++)
       {
           System.out.print(si[i]);
       }
   }
}