code: private void checkC() throws DatatypeException, IOException {
          if (context.length() == 0) {
              appendToContext(current);
          }
          current = reader.read();
          appendToContext(current);
          skipSpaces();
          boolean expectNumber = true;
  
          for (;;) {
              switch (current) {
                  default:
                      if (expectNumber)
                          reportNonNumber('C', current);
                      return;
  
                  case '+':
                  case '-':
                  case '.':
                  case '0':
                  case '1':
                  case '2':
                  case '3':
                  case '4':
                  case '5':
                  case '6':
                  case '7':
                  case '8':
                  case '9':
                      break;
              }
  
              checkArg('C', "x1 coordinate");
              skipCommaSpaces();
              checkArg('C', "y1 coordinate");
              skipCommaSpaces();
              checkArg('C', "x2 coordinate");
              skipCommaSpaces();
              checkArg('C', "y2 coordinate");
              skipCommaSpaces();
              checkArg('C', "x coordinate");
              skipCommaSpaces();
              checkArg('C', "y coordinate");
  
              expectNumber = skipCommaSpaces2();
          }
      }
docs: Checks a 'C' command.