laba4.2 (Java)

package com.company;
import java.io.*;
import java.util.Scanner;

public class Main {
    public static Scanner sysScan = new Scanner(System.in);
    static final int FILE = 1;
    static final int CONSOLE = 2;

    public static void main(String[] args) {
        System.out.println("""
        The program calculates the value of the function f(n).
        The function is defined on the set of natural numbers as follows:

        If n = 1, then f(n) = 1

                               n
        If n >= 2, then f(n) = ∑ (n div i)
                              i=2""");

        System.out.println("Choose way of input");
        int wayOfInput = chooseWayOfInputOutput();
        int argument = getArgument(wayOfInput);
        int result = findValueOfFunction(argument, argument);
        System.out.println("Choose way of output");
        int wayOfOutput = chooseWayOfInputOutput();
        outputResult(wayOfOutput, result);
        sysScan.close();
    }

    public static int chooseWayOfInputOutput() {
        System.out.println("Enter 1 or 2:\n 1.File\n 2.Console");
        Scanner scan = new Scanner(System.in);
        int choice = 0;
        boolean isIncorrect;
        do {
            isIncorrect = false;
            try {
                choice = Integer.parseInt(scan.nextLine());
            } catch (Exception e) {
                System.out.println("Enter an integer!");
                isIncorrect = true;
            }
            if (!isIncorrect && choice != FILE && choice != CONSOLE) {
                System.out.println("Enter 1 or 2!");
                isIncorrect = true;
            }
        } while (isIncorrect);
        return choice;
    }

    public static int getArgument(int way) {
        int argument = 0;
        switch (way) {
            case FILE:
                System.out.println("Enter the absolute link to the input file");
                String pathOfInput = getPath();
                argument = getArgumentFromFile(pathOfInput);
                break;
            case CONSOLE:
                argument = getArgumentFromConsole();
                break;
        }
        return argument;
    }

    public static String getPath() {
        Scanner scan = new Scanner(System.in);
        boolean isIncorrect;
        String path;
        do {
            isIncorrect = false;
            path = scan.nextLine();
            File file = new File(path);

            if (!file.exists()) {
                System.err.println("File not found!\nEnter the absolute link to the file");
                isIncorrect = true;
            }
        } while (isIncorrect);
        System.out.println();
        return path;
    }

    public static int getArgumentFromFile(String path) {
        System.out.println("Argument is reading from the file...");
        File fileOfInput = new File(path);
        String line;
        int argument = 0;
        boolean isIncorrect = false;
        if (fileOfInput.length() != 0) {
            try (BufferedReader reader = new BufferedReader(new FileReader(fileOfInput))) {
                line = reader.readLine();
                argument = Integer.parseInt(line);
            } catch (IOException e) {
                System.out.println("Input/output error!\nEnter the argument from console");
                isIncorrect = true;
            } catch (NumberFormatException e) {
                System.out.println("Incorrect data in the file!\nEnter the argument from console");
                isIncorrect = true;
            }
            if (!isIncorrect && argument < 1 || argument > 15000) {
                System.out.println("Incorrect data in the file!\nEnter the argument from console");
                isIncorrect = true;
            }
        } else {
            System.out.println("File is empty!\nEnter the argument from console");
            isIncorrect = true;
        }
        if (isIncorrect) {
            argument = getArgumentFromConsole();
        }
        return argument;
    }

    public static int getArgumentFromConsole() {
        System.out.println("Enter the argument of the function:");
        int argument = 0;
        boolean isIncorrect;
        do {
            isIncorrect = false;
            try {
                argument = Integer.parseInt(sysScan.nextLine());
            } catch (NumberFormatException e) {
                System.err.println("Enter the integer number!");
                isIncorrect = true;
            }
            if (!isIncorrect && (argument < 1 || argument > 15000)) {
                System.err.println("Enter the number in range [0; 15000]!");
                isIncorrect = true;
            }
        } while (isIncorrect);
        return argument;
    }

    public static void outputResult(int way, int result) {
        switch (way) {
            case FILE:
                System.out.println("Enter the absolute link to the output file");
                String pathOfOutput = getPath();
                try {
                    FileWriter writer = new FileWriter(pathOfOutput);
                    writer.write("The value of the function: " + result);
                    writer.close();
                } catch (IOException e) {
                    System.err.println("I/O Error!");
                }
                break;
            case CONSOLE:
                System.out.println("The value of the function: " + result);
                break;
        }
    }

    public static int findValueOfFunction(int n, int i) {
        if (n != 1) {
            if (i > 1) {
                return n/i + findValueOfFunction(n, i - 1 );
            } else {
                return 0;
            }
        } else {
            return 1;
        }
    }
}