laba_2_1_java

import java.util.Scanner;
public class pointInPolygon {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("The polygon is given by the coordinates of its vertices. Determine if the given point belongs to the area of the polygon.");
        System.out.println("Input number of vertices:");
        int n = 0;
        final int min = 3;
        boolean isIncorrect;
        do {
            isIncorrect = false;
            try {
                n = Integer.parseInt(scanner.nextLine());
            } catch (Exception e) {
                isIncorrect = true;
                System.out.println("Please, enter a positive integer number:");
            }
            if (!isIncorrect && (n < min))  {
                isIncorrect = true;
                System.out.println("There must be more than 2 vertices.");
            }
        } while (isIncorrect);
        float[] arrX = new float [n];
        float[] arrY = new float [n];
        int i;
        for (i = 0 ; i < n; i++){
            System.out.println("Enter coordinates for point " + (i + 1) + ":");
            do {
                isIncorrect = false;
                try {
                    arrX[i] = Float.parseFloat(scanner.nextLine());
                } catch (Exception e) {
                    isIncorrect = true;
                    System.out.println("Please, enter a number:");
                }
            } while (isIncorrect);
            do {
                isIncorrect = false;
                try {
                    arrY[i] = Float.parseFloat(scanner.nextLine());
                } catch (Exception e) {
                    isIncorrect = true;
                    System.out.println("Please, enter a number:");
                }
            } while (isIncorrect);
        }
        System.out.println("Input point coordinates:");
        float x = 0;
        float y = 0;
        do {
            isIncorrect = false;
            try {
                x = Float.parseFloat(scanner.nextLine());
            } catch (Exception e) {
                isIncorrect = true;
                System.out.println("Please, enter a number:");
            }
        }while (isIncorrect);
        do {
            isIncorrect = false;
            try {
                y = Float.parseFloat(scanner.nextLine());
            } catch (Exception e) {
                isIncorrect = true;
                System.out.println("Please, enter a number:");
            }
        } while (isIncorrect);
        scanner.close();
        boolean gotInto = false;
        int j = n - 1 ;
        for (i = 0; i < n; i++) {
            if ((((arrY[i] <= y) && (y <= arrY[j])) || ((arrY[j] <= y) && (y <= arrY[i]))) && (((arrY[j] - arrY[i]) != 0) && (x >= ((arrX[j] - arrX[i]) * (y - arrY[i]) / (arrY[j] - arrY[i]) + arrX[i]))))
                gotInto = !gotInto;
            j++;
            if (j == n)
                j = 0;
        }
        if (gotInto){
            System.out.println("Point belongs to area!");
        }
        else {
            System.out.println("Point doesn't belong to area.");
        }
    }
}