laba3.1 (Java)

package com.company;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws IOException {
        System.out.println("The program converts the number to the Roman numeral system");
        int source = chooseSourceOfInput();
        String sourceNumber = inputLine(source);
        String romanNumber = convertToRoman(sourceNumber);
        outputResult(source, romanNumber, sourceNumber);
    }

    public static int chooseSourceOfInput(){
        System.out.println("Choose where to enter data. 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 != 1 && choice != 2){
                System.out.println("Enter 1 or 2!");
                isIncorrect = true;
            }
        }while (isIncorrect);
        return choice;
    }

    public static String inputLine(int source) throws FileNotFoundException {
        String line = "";
        switch (source){
            case 1:
                System.out.println("Enter the absolute link to the input file");
                String pathInput = inputPath();
                line = inputLineFromFile(pathInput);
                break;
            case 2:
                line = inputLineFromConsole();
                break;
        }
        return line;
    }

    public static String inputPath(){
        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.out.println("File not found!\nEnter the absolute link to the file");
                isIncorrect = true;
            }
        }while (isIncorrect);
        System.out.println();
        return path;
    }

    public static String inputLineFromFile(String path) throws FileNotFoundException {
        File inputFile = new File(path);
        Scanner scan = new Scanner(inputFile);
        String line;

        if (inputFile.length() != 0){
            line = scan.nextLine();
        }else{
            System.out.println("The line is missing from your file!\nEnter line from console ");
            line = inputLineFromConsole();
        }
        boolean isIncorrect = checkLine(line);
        if (isIncorrect) {
            line = inputLineFromConsole();
        }
        return line;
    }

    public static boolean checkLine (String line) {
        boolean flag = false;
        int number = 0;

        if (line.length() == 0){
            System.out.println("You entered an empty line!\nRepeat enter");
            flag = true;
        }
        if (!flag) {
            try {
                number = Integer.parseInt(line);
            } catch (NumberFormatException e) {
                System.out.println("This line cannot be represented as an integer!\nEnter line from console ");
                flag = true;
            }
        }
        if ((number < 1 || number > 2000) && !flag) {
            System.out.println("The number must be in the range from 1 to 2000\nEnter line from console ");
            flag = true;
        }
        return flag;
    }

    public static String inputLineFromConsole() {
        Scanner scan = new Scanner(System.in);
        boolean isIncorrect;
        String line;
        System.out.println("Enter the line");
        do {
            isIncorrect = false;
            line = scan.nextLine();
            isIncorrect = checkLine(line);
        }while (isIncorrect);
        return line;
    }

    public static String convertToRoman(String sourceNumber){
        String[] unitsOfRoman = {"","I","II","III","IV","V","VI","VII","VIII","IX"};
        String[] tensOfRoman = {"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"};
        String[] hundredsOfRoman = {"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"};
        String[] thousandsOfRoman = {"","M","MM"};

        int j = 0;
        int[] digits = new int[4];
        for (int i = 4 - sourceNumber.length(); i < 4; i++) {
            digits[i] = Integer.parseInt(String.valueOf(sourceNumber.charAt(j)));
            j++;
        }
        String romanNumber = thousandsOfRoman[digits[0]] + hundredsOfRoman[digits[1]] + tensOfRoman[digits[2]] + unitsOfRoman[digits[3]];
        return romanNumber;
    }

    public static void outputResult(int source, String romanNumber, String sourceNumber ) throws IOException {
        if (source == 1) {
            System.out.println("\nEnter the absolute link to the output file");
            String pathOutput = inputPath();
            outputToFile(pathOutput, romanNumber, sourceNumber);
        }else {
            outputToConsole(romanNumber, sourceNumber);
        }
    }

    public static void outputToFile(String path, String romanNumber, String sourceNumber) throws IOException {
        FileWriter writer = new FileWriter(path);
        writer.write(sourceNumber + " = " +  romanNumber);
        writer.close();
        System.out.println("The data is successfully recorded in the file");
    }

    public static void outputToConsole(String romanNumber, String sourceNumber){
        System.out.println(sourceNumber + " = " +  romanNumber);
    }
}