Orthogonal Triangle

import java.io.File; // Import the File class
import java.io.FileNotFoundException; // Import this class to handle errors
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner; // Import the Scanner class to read text files

public class Orthogonal_Triangle {

    private int[][] matrix;
    private int rows, cols;
    private ArrayList < Integer > sums;

    /**
     * Default constructor that initializes an empty integer matrix
     * @param rows Number of rows
     * @param cols Number of columns
     */
    public Orthogonal_Triangle(int rows, int cols) {
        // Create new integer matrix
        matrix = new int[rows][cols];
        this.rows = rows;
        this.cols = cols;

        // Create array list for sums
        sums = new ArrayList < Integer > ();


        // Fill matrix with minus 1s so it is empty
        for (int i = 0; i < this.rows; i++) {
            for (int j = 0; j < this.cols; j++) {
                matrix[i][j] = -1;
            }
        }
    }

    public static void main(String[] args) {
        Orthogonal_Triangle ot = new Orthogonal_Triangle("filename.txt", " ");
        ot.print();
        ot.traverse(0, 0, 0);
        System.out.println("Maximum = " + ot.getMax());
    }

    /**
     * Constructor that reads file and creates integer matrix with given data
     * @param filename File name
     * @param seperator Seperator to split string into values
     */
    public Orthogonal_Triangle(String filename, String seperator) {

        // Get number of lines in file
        Path path = Paths.get(filename);

        long lines = 0;
        try {
            lines = Files.lines(path).count();

        } catch (IOException e) {
            e.printStackTrace();
        }

        // Determine rows and cols by number of lines
        this.rows = (int) lines;
        this.cols = (int) lines;

        // Create matrix
        matrix = new int[rows][cols];

        // Create array list for sums
        sums = new ArrayList < Integer > ();

        // Fill matrix with minus 1s so it is empty
        for (int i = 0; i < this.rows; i++) {
            for (int j = 0; j < this.cols; j++) {
                matrix[i][j] = -1;
            }
        }

        // Read file and fill matrix with given data
        try {
            File myObj = new File(filename);
            Scanner myReader = new Scanner(myObj);

            int i = 0;

            while (myReader.hasNextLine()) {
                String data = myReader.nextLine();
                String[] arrOfStr = data.split(seperator);

                int j = 0;
                for (String a: arrOfStr) {
                    matrix[i][j] = Integer.parseInt(a);
                    j++;
                }
                i++;
            }

            myReader.close();
        } catch (FileNotFoundException e) {
            System.out.println("An error occurred.");
            e.printStackTrace();
        }

    }

    /**
     * Simple print method for integer matrix
     */
    public void print() {
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                if (matrix[i][j] != -1)
                    System.out.print(matrix[i][j] + " ");
            }
            System.out.print("\n");
        }
    }

    /**
     * Check if a number is prime or not
     * @param number Number to check
     * @return Status of being number prime
     */
    private boolean isPrime(int number) {
        boolean result = true;

        // Zero and one are not prime
        if (number == 0 || number == 1)
            result = false;

        for (int i = 2; i <= number / 2; i++) {
            if (number % i == 0)
                result = false;
        }
        return result;
    }

    /**
     * Traverses in integer matrix downward and digonally, calculates sum of numbers
     * @param x Position of x
     * @param y Position of y
     * @param total Sum of numbers
     */
    public void traverse(int x, int y, int total) {
        // Base case: if it is last row in matrix
        if (x == rows - 1) {
            sums.add(total + matrix[x][y]);
        } // Base case: if all three downward and diagonal adjacents are prime
        else if ((y - 1 >= 0 && isPrime(matrix[x + 1][y - 1])) && isPrime(matrix[x + 1][y]) && (y + 1 <= x + 1 && isPrime(matrix[x + 1][y + 1]))) {
            sums.add(total + matrix[x][y]);
        } else {
            // Traversing left diagonal
            if (y - 1 >= 0)
                if (!isPrime(matrix[x + 1][y - 1]))
                    traverse(x + 1, y - 1, total + matrix[x][y]);

            // Traversing downward
            if (!isPrime(matrix[x + 1][y]))
                traverse(x + 1, y, total + matrix[x][y]);

            // Traversing right diagonal
            if (y + 1 <= x + 1 && !isPrime(matrix[x + 1][y + 1]))
                if (!isPrime(matrix[x + 1][y + 1]))
                    traverse(x + 1, y + 1, total + matrix[x][y]);
        }
    }

    /**
     * Returns maximum integer value in a collection.
     * @return Maximum value
     */
    public int getMax() {
        Integer max = Collections.max(sums);
        return max;
    }

}