code: public static char toChar(final String str) {
          Validate.isTrue(StringUtils.isNotEmpty(str), "The String must not be empty");
          return str.charAt(0);
      }
docs: <p>Converts the String to a char using the first character, throwing
  an exception on empty Strings.</p>
  
  <pre>
  CharUtils.toChar("A")  = 'A'
  CharUtils.toChar("BA") = 'B'
  CharUtils.toChar(null) throws IllegalArgumentException
  CharUtils.toChar("")   throws IllegalArgumentException
  </pre>
  
  @param str  the character to convert
  @return the char value of the first letter of the String
  @throws IllegalArgumentException if the String is empty