Java Creating a vector with multiple ends

Question

I want to create two types of vectors (as classes):

• The first type is a regular vector with two components (a start and an ending point).
• The second type is also a vector but instead of having one it has two ending points you can switch between.

My idea was to create an abstract superclass (e.g. AbstractVector) in which I define the common functions of the vectors:

abstract class AbstractVector {
    //Methods, e.g. length(), getter...
}

Then my two subclasses Vector and (e.g. ) TriVector extend the above class. The problem I'm facing is handling of the two ending points in the TriVector class. I absolutely have no idea on how to do it or how to set up the abstract class correctly so I can have a normal vector and a vector with two endings between which I can switch (e.g. the TriVector class has a method switch() which switches between the two ending points).

I hope somebody can help me or propose a better solution.

Answer 1

A very rough sketch for a solution, only detailing the getStart() and getEnd() methods:

abstract class AbstractVector {
    protected Point startPoint;
    public Point getStart() {
        return startPoint;
    }
    public abstract Point getEnd();
    //Methods, e.g. length(), getter...
}

class Vector extends AbstractVector {
    protected Point endPoint;
    public Point getEnd() {
        return endPoint;
    }
}

class TriVector extends AbstractVector {
    protected Point[] endPoints = new Point[2];
    protected int activeEndPoint = 0;

    public Point getEnd() {
        return endPoints[activeEndPoint];
    }

    public void switchEnds() {
        activeEndPoint = 1 - activeEndPoint;
    }
}