What the index means? in setCoordinate(int index...?

843799

What the index means? in setCoordinate(int index...?
Although I looked at the API manual, but I still don't get it.
public void setCoordinate(int index,
double[] coordinate)
Sets the coordinate associated with the vertex at the specified index.
Parameters:
index - destination vertex index in this geometry array
coordinate - source array of 3 values containing the new coordinate

843799

When you create geometry via a GeometryArray object the coords are stored in an array in which the order is important (eg a tri strip uses the last 2 coords and the current to draw a triangle, a tri fan uses the first, last and current to draw a triangle).

That method allows you to overwrite a coord at a specific point to change the geometry.