Java Reference
In-Depth Information
Try It Out - The
PolyLine
Class
We can define the
PolyLine
class to use the
ListPoint
class as follows:
public class PolyLine {
// Construct a polyline from an array of points
public PolyLine(Point[] points) {
if(points != null) { // Make sure there is an array
// Create a one point list
start = new ListPoint(points[0]); // 1st point is the start
end = start; // as well as the end
// Now add the other points
for(int i = 1; i < points.length; i++)
addPoint(points[i]);
}
}
// Add a Point object to the list
public void addPoint(Point point) {
ListPoint newEnd = new ListPoint(point); // Create a new ListPoint
if(start == null)
start = newEnd; // Start is same as end
else
end.setNext(newEnd); // Set next variable for old end as new end
end = newEnd; // Store new point as end
}
// String representation of a polyline
public String toString() {
StringBuffer str = new StringBuffer("Polyline:");
ListPoint nextPoint = start; // Set the 1st point as start
while(nextPoint != null) {
str.append(" "+ nextPoint); // Output the current point
nextPoint = nextPoint.getNext(); // Make the next point current
}
return str.toString();
}
private ListPoint start; // First ListPoint in the list
private ListPoint end; // Last ListPoint in the list
}
You might want to be able to add a point to the list by specifying a coordinate pair. You could overload
the
addPoint()
method to do this:
// Add a point to the list
public void addPoint(double x, double y) {
addPoint(new Point(x, y));
}
We just create a new
Point
object in the expression that is the argument to the other version of
addPoint()
.
