code: public StrBuilder appendPadding(final int length, final char padChar) {
          if (length >= 0) {
              ensureCapacity(size + length);
              for (int i = 0; i < length; i++) {
                  buffer[size++] = padChar;
              }
          }
          return this;
      }
docs: Appends the pad character to the builder the specified number of times.
  
  @param length  the length to append, negative means no append
  @param padChar  the character to append
  @return this, to enable chaining