Here we explicitly use the pointer this to explicitly dereference the invoking object. Fortunately, the compiler automatically ``inserts'' these dereferences for class
members, hence, we really can use the first definitions of setX() and setY(). However, it sometimes make sense to know that there is a pointer this available which
indicates the invoking object.
Currently, we need to call the set methods to initialize a point object. However, we would like to initialize the point when we define it. We therefore use special
methods called constructors.