package com.company;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {

        final int MAX_ITER = 100;
        final double FirstCoef = 9.33;
        final double SecondCoef = 6.977;
        final double ThirdCoef = 7.25;
        double a;
        double b;
        double Accuracy;
        double Difference;
        double x0;
        double fFromDeltaMinus;
        double fFromDeltaPlus;
        double fFromx0;
        double Convergence;
        int k = 0;
        boolean IsCorrect;
        System.out.println("Subject: Find the roots of the equation 9.33sin(6.977x) - 7.25x = 0 with Epsilon accuracy by a simple iteration");
        do {
            System.out.printf("Enter the span boundaries [a;b] \n");
            a = input();
            b = input();
            Convergence = (FirstCoef * Math.sin(SecondCoef * a) / 7.25) * (FirstCoef * Math.sin(SecondCoef * b) / ThirdCoef);
            if (Convergence < 0) {
                System.out.printf("Iteration process converges \n");
                IsCorrect = true;
            } else {
                System.out.printf("Iteration process does not converge \n");
                IsCorrect = false;
            }
        } while (!IsCorrect);
        System.out.printf("Enter accuracy value (Epsilon) \n");
        Accuracy = input();
        if ((Accuracy > 0) && (Accuracy < 1)) {
            IsCorrect = true;
        } else {
            IsCorrect = false;
        }
        while (!IsCorrect) {
            System.out.printf("Accuracy value must lie between (0;1) \n");
            Accuracy = input();
        }
        x0 = ((a + b) / 2);
        while ((Accuracy < Math.abs(a - x0)) || (k > MAX_ITER)) {
            fFromDeltaMinus = FirstCoef * Math.sin(SecondCoef * (a - Accuracy)) / ThirdCoef;
            fFromDeltaPlus = FirstCoef * Math.sin(SecondCoef * (a + Accuracy)) / ThirdCoef;
            Difference = -(fFromDeltaPlus - fFromDeltaMinus) / (2 * Accuracy);
            x0 = a;
            fFromx0 = FirstCoef * Math.sin(SecondCoef * x0) / ThirdCoef;
            a = x0 + fFromx0 / Difference;
            k = k + 1;
            System.out.printf("C= %.6f ", a);
            System.out.printf("f(c)= %.6f \n", fFromx0);
        }
        if (Accuracy > Math.abs(a - x0)) {
            System.out.printf("C= %.6f ", a);
            System.out.printf("Number of iterations: %d \n ", k);
        } else {
            System.out.printf("Answer not found!");
        }
    }

    public static float input() {
        Scanner scan = new Scanner(System.in);
        float value = 1;
        try {
            value = scan.nextFloat();
            return value;
        } catch (Throwable error) {
            System.out.println("Ошибка! Введите число: ");
            return input();
        }
    }
}