public class ReplaceCheck
{
   /**
      A method to replace letters as follows:
      the letter e becomes 3, the letter i becomes 1,
      the letter l becomes 7, and the letter o becomes 0.
      @param str a string
      @return the string with the characters replaced
   */
   public static String replace(String str)
   {
      String result = "";
      for(int i = 0; i < str.length(); i++)
      {
         switch(str.charAt(i))
         {
         case 'e':
            result += '3';
            break;
         case 'i':
            result += '1';
            break;
         case 'l':
            result += '7';
            break;
         case 'o':
            result += '0';
            break;
         default:
            result += str.charAt(i);
            break;
         }
      }
      return result;
   }
}