Java Reference
In-Depth Information
Try It Out - The
ListPoint
Class
We can define the
ListPoint
class using the class
Point
with the code:
public class ListPoint {
// Constructor
public ListPoint(Point point) {
this.point = point; // Store point reference
next = null; // Set next ListPoint as null
}
// Set the pointer to the next ListPoint
public void setNext(ListPoint next) {
this.next = next; // Store the next ListPoint
}
// Get the next point in the list
public ListPoint getNext() {
return next; // Return the next ListPoint
}
// Return String representation
public String toString() {
return "(" + point + ")";
}
private ListPoint next; // Refers to next ListPoint in the list
private Point point; // The point for this list point
}
How It Works
A
ListPoint
object is a means of creating a list of
Point
objects that originate elsewhere so we don't need
to worry about duplicating
Point
objects stored in the list. We can just store the reference to the
Point
object passed to the constructor in the data member,
point
. The data member,
next
, should contain a
reference to the next
ListPoint
in the list, and since that is not defined here, we set
next
to
null
.
The
setNext()
method will enable the
next
data member to be set for the existing last point in the
list, when a new point is added to the list. A reference to the new
ListPoint
object will be passed as
an argument to the method. The
getNext()
method enables the next point in the list to be
determined, so this method is the means by which we can iterate through the entire list.
By implementing the
toString()
method for the class, we enable the automatic creation of a
String
representation for a
ListPoint
object when required. Here we differentiate the
String
representation of
our
ListPoint
object by enclosing the
String
representation of
point
between parentheses.
We could now have a first stab at implementing the
PolyLine
class.
