L Question: Get Interval Range

public class IntervalsImpl implements Intervals {

    List<Point> list = new ArrayList<Point>();

    public static void main(String... args) {
        IntervalsImpl obj = new IntervalsImpl();
        obj.addIntervals(3, 6);
        obj.addIntervals(8, 9);
        obj.addIntervals(1, 5);
        obj.addIntervals(1, 3);
        obj.addIntervals(1, 8);
        obj.addIntervals(3, 10);
        obj.addIntervals(15, 25);


        System.out.println(obj.getTotalCoveredLength());
    }


    @Override
    public void addIntervals(int x, int y) {


        list.add(new Point(x, y));

    }

    @Override
    public int getTotalCoveredLength() {
        Collections.sort(list);

        int totalLen = 0;
        Point lastPoint = new Point(0, 0);

        for (Point point : list) {

            if (point.x > lastPoint.y) {   //located apart
                totalLen += point.y - point.x;
                lastPoint = point;

            } else if (point.x == lastPoint.x && lastPoint.y < point.y) { //start from same origin

                totalLen += point.y - lastPoint.y;

                lastPoint = point;


            } else if (point.x < lastPoint.y && point.y > lastPoint.y) { //in between
                totalLen += point.y - lastPoint.y;
                lastPoint = point;
            }


        }

        return totalLen;
    }


}

class Point implements Comparable<Point> {

    public int x, y;


    Point(int x, int y) {
        if (x > y)
            throw new IllegalArgumentException("x can't be greater than y");

        this.x = x;
        this.y = y;
    }


    @Override
    public int compareTo(Point o) {
        return o == null ? 0 : (this.x - o.x);
    }

}