task6_v

package com.company;

/*
    task 6
    problem 4
 */

import java.util.Locale;
import java.util.Scanner;

public class Main {

    public static final String ENTER_N = "n:";
    public static final String ENTER_X = "x:";
    public static final String ENTER_E = "e:";


    public static int getInt(Scanner scanner){
        while (!scanner.hasNextInt()){
            System.out.println("error");
            scanner.next();
        }
        return scanner.nextInt();
    }

    public static double getDouble(Scanner scanner){
        while (!scanner.hasNextDouble()){
            System.out.println("error");
            scanner.next();
        }
        return scanner.nextDouble();
    }

    public static double get_a(double x, int n){

        if(n % 2 == 0){
            return -Math.pow(x,1+2*(n-1))/(1+2*(n-1));
        }
        else{
            return Math.pow(x,1+2*(n-1))/(1+2*(n-1));
        }
    }

    public static double sum_n(int n, double x){
        double sum = 0;

        for(int i = 1; i <n; i++){
            sum += get_a(x,i);
        }
        return  sum;
    }

    public static double sum_e(double e, double x){
        double sum = 0;
        int i = 1;
        while (true){
            double t = get_a(x,i);
            if(Math.abs(t) >= Math.abs(e)){
                sum += t;
                i++;
            }
            else{
                break;
            }
        }
        return sum;
    }

    public static double sum_e_10(double e, double x){
        double sum = 0;
        int i = 1;
        while (true){
            double t = get_a(x,i);
            if(Math.abs(t) >= Math.abs(e/10)){
                sum += t;
                i++;
            }
            else{
                break;
            }
        }
        return sum;
    }

    public static double calc(double x){
        return Math.atan(x);
    }


    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        Locale.setDefault(Locale.ROOT);

        System.out.println(ENTER_N);
        int n = getInt(scanner);
        while(!(n>0)){
            n = getInt(scanner);
        }


        System.out.println(ENTER_X);
        double x = getDouble(scanner);
        while(!(x > 0.0 && x < 1.0)){
            x = getInt(scanner);
        }


        System.out.println(ENTER_E);
        double e = getDouble(scanner);
        while(!(e>0)){
            e = getInt(scanner);
        }

        System.out.println(sum_n(n,x));
        System.out.println(sum_e(e,x));
        System.out.println(sum_e_10(e,x));
        System.out.println(calc(x));

    }
}