code: public static boolean isBlank(CharSequence cs) {
      int strLen;
      if (cs == null || (strLen = cs.length()) == 0) { return true; }
      for (int i = 0; i < strLen; i++) {
        if (Character.isWhitespace(cs.charAt(i)) == false) { return false; }
      }
      return true;
    }
docs: <p>
  Checks if a CharSequence is whitespace, empty ("") or null.
  </p>
  
  <pre>
  isBlank(null)      = true
  isBlank("")        = true
  isBlank(" ")       = true
  isBlank("bob")     = false
  isBlank("  bob  ") = false
  </pre>
  
  @param cs
  the CharSequence to check, may be null
  @return {@code true} if the CharSequence is null, empty or whitespace
  @since 3.0