code: public StrBuilder deleteAll(final String str) {
          final int len = (str == null ? 0 : str.length());
          if (len > 0) {
              int index = indexOf(str, 0);
              while (index >= 0) {
                  deleteImpl(index, index + len, len);
                  index = indexOf(str, index);
              }
          }
          return this;
      }
docs: Deletes the string wherever it occurs in the builder.
  
  @param str  the string to delete, null causes no action
  @return this, to enable chaining