4.2

import java.util.Scanner;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import static java.lang.Math.pow;

public class Main {
    private static float yNext;
    private static int x;
    private static float eps;

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        System.out.println("This program finds square root of a number using Newton's method.");
        int inputMethodChoice = chooseInputMethod(scanner);
        float root;

        if (inputMethodChoice == 1) {
            inputDataManually(scanner);
        } else if (inputMethodChoice == 2) {
            String filePath = findFile(scanner);
            inputDataFromFile(filePath);
        }
        findSquareRoot(1);
        outputAnswer();
        writeToFile(scanner);

        scanner.close();

    }

    private static void outputAnswer() {

        System.out.println("Square root of x = " + yNext);
    }
    private static int chooseInputMethod(Scanner scanner) {
        int choice;
        do {
            System.out.println("Choose an option:");
            System.out.println("1. Input data manually");
            System.out.println("2. Read data from a text file");

            while (!scanner.hasNextInt()) {
                System.out.println("Invalid input. Please enter 1 or 2.");
                scanner.next();
            }
            choice = scanner.nextInt();
            scanner.nextLine();
            if (choice != 1 && choice != 2) {
                System.out.println("Error! You have to input either 1 or 2.");
            }
        } while (choice != 1 && choice != 2);
        return choice;
    }

    private static void inputDataManually(Scanner scanner) {
        do {
            System.out.println("Input the X value:");

            while (!scanner.hasNextInt()) {
                System.out.println("Invalid input. Please enter a number.");
                scanner.next();
            }
            x = scanner.nextInt();
            scanner.nextLine();
            if (x < 0 || x > 1000000) {
                System.out.println("Error! You have to input number that is bigger than 0 and smaller than 1 000 000.");
            }
        } while (x < 0 || x > 1000000);

        do {
            System.out.println("Input Epsilon value:");

            while (!scanner.hasNextFloat()) {
                System.out.println("Invalid input. Please enter a number.");
                scanner.next();
            }
            eps = scanner.nextFloat();
            scanner.nextLine();
            if (eps < 0 || eps >= 1) {
                System.out.println("Error! You have to input number that is bigger than 0 and smaller than 1.");
            }
        } while (eps < 0 || eps >= 1);
    }

    private static void findSquareRoot(float yPrev) {
        float temp;
        yNext = (float) (0.5 * (yPrev + x / yPrev));
        if (Math.abs(yNext - yPrev) > eps) {
            temp = yNext;
            findSquareRoot(temp);
        }
    }

    private static String findFile(Scanner scanner) {
        String filePath;
        boolean isCorrect;
        do {
            isCorrect = true;
            System.out.print("Enter path to the file: ");
            filePath = scanner.nextLine();
            File file = new File(filePath);
            if (!file.exists()) {
                isCorrect = false;
                System.out.println("File not found at the specified path.");
            } else if (!filePath.endsWith(".txt")) {
                isCorrect = false;
                System.out.println("Error, wrong file type! File should have .txt extension.");
            }
        } while (!isCorrect);
        System.out.println("File found.");
        return filePath;
    }
    private static void inputDataFromFile(String path) {
        float base;
        float power;
        double temp;

        try (Scanner fileScanner = new Scanner(new File(path))) {
            System.out.println("Reading file...");

            String line = fileScanner.nextLine();
            String[] parts = line.split(" ");

            base = Float.parseFloat(parts[0]);

            line = fileScanner.nextLine();
            parts = line.split(" ");

            power = Float.parseFloat(parts[0]);

            line = fileScanner.nextLine();
            parts = line.split(" ");

            x = Integer.parseInt(parts[0]);

            temp = base*Math.pow(10, -1*power);
            eps = (float) temp;

        } catch (IOException e) {
            System.out.println("Error reading file!");
        }
    }
    private static void writeToFile(Scanner scanner) {
        try {
            System.out.print("Enter file name: ");
            String fileName = scanner.nextLine();
            fileName += ".txt";
            FileWriter writer = new FileWriter(fileName);

            writer.write("Square root of x = " + yNext);

            writer.close();

            System.out.println("Results written to " + fileName);
        } catch (IOException e) {
            System.out.println("Error writing to file!");
        }
    }
}