code: public static boolean isEmpty(final CharSequence str) {
          if ( str == null || str.length() == 0 ) {
              return true;
          }
          
          for ( int i = 0, length = str.length(); i < length; i++ ){
              if ( !isWhitespace(str.charAt( i )) )  {
                  return false;
              }
          }
          
          return true;
      }
docs: <p>Checks if a String is empty ("") or null.</p>
  
  <pre>
  StringUtils.isEmpty(null)      = true
  StringUtils.isEmpty("")        = true
  StringUtils.isEmpty(" ")       = false
  StringUtils.isEmpty("bob")     = false
  StringUtils.isEmpty("  bob  ") = false
  </pre>
  
  <p>NOTE: This method changed in Lang version 2.0.
  It no longer trims the String.
  That functionality is available in isBlank().</p>
  
  @param str  the String to check, may be null
  @return <code>true</code> if the String is empty or null