csc-220 polyHW For Luis

/*
 * Name:
 * Date:
 * Course Number:
 * Course Name:
 * Problem Number:
 * Email:
 * Short Description of the Problem
 */

import java.util.Scanner;
import java.lang.*;

public class polygonHW {


    //**********************************************

    public static void main(String[] args) {
        int size;

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter number of points (must be more than 3)");
        size = sc.nextInt();


        Double[] x = new Double[size];
        Double[] y = new Double[size];
        getPoints(sc, x,y);
        printPoints(x,y);
        printArea(x,y);


    }

    // Important stuff is in this method
    private static void printArea(Double[] x, Double[] y) {

        double theta = 0;
        double hyp = 0;
        double base = 0;
        double height = 0;
        double Area = 0;

        //calls orient method
        x = orientArr(x);
        y = orientArr(y);


        //loop runs two less times than the array length, always starts at [1] because [0] is now the origin (0,0)
        //The idea is that one point will always be 0,0 so we just need to worry about two points at a time
        for(int i = 1; i < x.length -1 ; i++ )
        {
            base = simpleDist(x[i] , y[i]);
            hyp = simpleDist(x[i+1] , y[i+1]);

            //subtracts arctan of theta point 1 with respect to origin from theta point 2 with respect to origin, gives us the angle of the triangle near the origin
            theta = Math.atan2(y[i], x[i]) - Math.atan2(y[i+1], x[i+1]);

            height = Math.sin(theta) * hyp;

            //Heron's Formula I think he said he wanted to return an error if this produces a negative number
            // not sure though, it might be more complicated
            Area += (base * height)/2;
        }

        System.out.println("Area = " + Area);

    }


    //sets points stored at [0] as origin
    private static Double[] orientArr(Double[] x) {

        double xCancel = x[0];

        for(int i = 0; i < x.length ; i++ )
        {
            x[i] -= xCancel;
        }

        return x;
    }

    // returns a point's distance from origin
    private static double simpleDist(Double x, Double y) {

    return  Math.sqrt(Math.pow(x,2d) + Math.pow(y,2));

    }

    private static void printPoints(Double[] x, Double[] y) {
        System.out.println("Collected Points");
        for(int i = 0; i < x.length ; i++ ) {
            System.out.println(x[i] +" , " +  y[i]);
        }

    }

    private static void getPoints(Scanner sc, Double[] x, Double[] y) {

        for(int i = 0; i < x.length ; i++ ) {

            x[i] = sc.nextDouble();
            y[i] = sc.nextDouble();
        }


    }


}