java程式設計題目---字母處理【大寫轉小寫小寫轉大寫】

Write the following method that returns a new string in which the uppercase are changed to lowercace and lowercace to uppercase.
EX: enter: aBcD ，output: AbCd。

import java.util.Scanner;
 
public class C1 {
 
 public static void main(String[] args) 
 {
  Scanner input = new Scanner(System.in);//提示使用者輸入並輸入字串
    
  System.out.println("請輸入字串");
  String a = input.next();
    
  System.out.println(swapCase(a));  
  
 }
 
 public static String swapCase(String s)//將字串大轉小，小轉大
 {
  String u = s.toUpperCase();
  String l = s.toLowerCase();
  String a = "";
   
  for(int i = 0 ; i < s.length() ; i++ )
  {
   if(s.charAt(i) != u.charAt(i))
   {
   a = a + u.charAt(i);
   }
   else
   a = a + l.charAt(i);
  }
  return a ;//回傳結果
 
 }
}