Extending Classes and Inheritance - Beginning Java - page 313

ListPoint object in its next member, which in turn contains a reference to the next, and so on through to
the last ListPoint object. You know it is the last one because its next member, which usually points to the
next ListPoint object, is null . Let's try it.

TRY IT OUT: The ListPoint Class
You can define the ListPoint class using the Point class with the following 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
@Override
public String toString() {
return "(" + point + ")";

}

private ListPoint next; // Refers to next ListPoint in

the list
private Point point; // The point for this list

point
}

Directory "TryPolyLine"

Save this file in the same directory as the Point class, TryPolyLine .
How It Works
A ListPoint object is a means of creating a list of Point objects that originate elsewhere so you don't
need to worry about duplicating Point objects stored in the list. You can just store the reference to the
Point object passed to the constructor in the data member, point . The data member, next , should con-
tain a reference to the next ListPoint in the list, and because that is not defined here, you set next to
null .