code: public void append(final StringBuffer sb) {
          if (sb == null) {
              return;
          }
          provideCapacity(length + sb.length());
          sb.getChars(0, sb.length(), c, length);
          length += sb.length();
      }
docs: Appends <code>sb</code> to the end of this CharBuffer.
  This method involves copying the new data once!
  @param sb the StringBuffer to append or null