The javadoc of ArcTo is mostly on the form

void setX() - Sets the property X.
void setY() - Sets the property Y.

what is really needed is an explanation of what X and Y means, preferably with drawings that illustrate what effect advanced concepts such as sweepFlag and largeFlag has.

A really good example on how to document a complex problem elegantly can be found in class FillRule which has really helpful illustrations.