code: final protected void putChar(char c) {
          final int clen = _internalBuffer.length;
          if (clen == _bufferPosition) {
              final char[] next = new char[2 * clen + 1];
  
              System.arraycopy(_internalBuffer, 0, next, 0, _bufferPosition);
              _internalBuffer = next;
          }
  
          _internalBuffer[_bufferPosition++] = c;
      }
docs: Store the char in the internal buffer