Question

I need help with 11.15 Area convex polygon in introduction to Java programming and data structures. I havent had any luck creaating it effectivly.

(The Course class) Rewrite the Course class in Listing 10.6. Use an Array List to replace an array to store students. Draw the new UML diagram for tde class. You should not change the original contract of the Course class (ie, the definition of the constructors and methods should not be changed, but the private members may be changed .)

Answer 1

Here is a program of Area Convex polygen Hope it wil help you

public class MyPoint {

    public double x;
    public double y;

    public MyPoint(double x, double y) {
        this.x = x;
        this.y = y;
    }

    public MyPoint() {
        this(0,0);
    }

    public double x() {
        return x;
    }

    public void setX(double x) {
        this.x = x;
    }

    public double y() {
        return y;
    }

    public void setY(double y) {
        this.y = y;
    }

    public double distance(double x, double y) {
        return Math.sqrt((this.x - x) * (this.x - x) + (this.y - y) * (this.y - y));
    }

    public double distance(MyPoint point) {

        return distance(point.x, point.y);
    }

    public MyPoint getCenterPoint(MyPoint p) {

        return new MyPoint((p.x + this.x) / 2, (p.y + this.y) / 2);
    }

    public static MyPoint getCenterPoint(double x1, double y1, double x2, double y2) {
        return new MyPoint((x1 + x2) / 2, (y1 + y2) / 2);
    }

    /** Return true if this point is on the left side of the
     *  directed line from p0 to p1 */
    public boolean leftOfTheLine(MyPoint p0, MyPoint p1) {

        return leftOfTheLine(p0.x, p0.y, p1.x, p1.y, x, y);
    }

    /** Return true if this point is on the same
     *  line from p0 to p1 */
    public boolean onTheSameLine(MyPoint p0, MyPoint p1) {

        return onTheSameLine(p0.x, p0.y, p1.x, p1.y, x, y);

    }

    /** Return true if this point is on the right side of the
     *  directed line from p0 to p1 */
    public boolean rightOfTheLine(MyPoint p0, MyPoint p1) {

        return rightOfTheLine(p0.x, p0.y, p1.x, p1.y, x, y);

    }

    /** Return true if this point is on the
     *  line segment from p0 to p1 */
    public boolean onTheLineSegment(MyPoint p0, MyPoint p1) {

        return onTheLineSegment(p0.x, p0.y, p1.x, p1.y, x, y);

    }


    /** Return true if point (x2, y2) is on the left side of the
     *  directed line from (x0, y0) to (x1, y1) */
    public static boolean leftOfTheLine(double x0, double y0, double x1, double y1, double x2, double y2){

        return (x1 - x0) * (y2 - y0) - (x2 - x0) * (y1 - y0) > 0;
    }
    /** Return true if point (x2, y2) is on the same
     *  line from (x0, y0) to (x1, y1) */
    public static boolean onTheSameLine(double x0, double y0, double x1, double y1, double x2, double y2) {

        return (x1 - x0) * (y2 - y0) - (x2 - x0) * (y1 - y0) == 0;
    }
    /** Return true if point (x2, y2) is on the
     *  line segment from (x0, y0) to (x1, y1) */
    public static boolean onTheLineSegment(double x0, double y0, double x1, double y1, double x2, double y2) {

        double position = (x1 - x0) * (y2 - y0) - (x2 - x0) * (y1 - y0);

        return position <= 0.0000000001 && ((x0 <= x2 && x2 <= x1) || (x0 >= x2 && x2 >= x1));
    }

    /** Return true if point (x2, y2) is on the right side of the
     *  directed line from (x0, y0) to (x1, y1) */
    public static boolean rightOfTheLine(double x0, double y0, double x1, double y1, double x2, double y2){

        return (x1 - x0) * (y2 - y0) - (x2 - x0) * (y1 - y0) < 0;
    }

    @Override
    public String toString() {
        return "(" + x + ", " + y + ")";
    }

}

import java.util.ArrayList;
import java.util.Scanner;

public class Exercise_15 {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        System.out.print("Enter the number of the points: ");
        int numOfPoints = input.nextInt();

        System.out.print("Enter the coordinates of the points: ");
        ArrayList<MyPoint> points = new ArrayList<>();
        for (int i = 0; i < numOfPoints; i++) {
            points.add(new MyPoint(input.nextDouble(), input.nextDouble()));
        }


        System.out.println("The total area is " + getConvexPolygonArea(points));

    }

    //  Area of a Convex Polygon
    // http://www.mathwords.com/a/area_convex_polygon.htm
    public static double getConvexPolygonArea(ArrayList<MyPoint> points) {
        // points must be counter clockwise
        double sum1 = 0;
        double sum2 = 0;
        for (int i = 0; i < points.size(); i++) {
            int limitIndex = (i + 1) % points.size();
            MyPoint p1 = points.get(i);
            MyPoint p2 = points.get(limitIndex);
            System.out.println("P1 index = " + i);
            System.out.println("P2 index =" + limitIndex);
            sum1 += (p1.x * p2.y);
            sum2 += (p1.y * p2.x);
        }

        double area = 0.5 * (sum1 - sum2);
        return (area > 0) ? area : -area;
    }

}