CODEWITHSUNDEEP
javafractions
PRANAVA K P
PRANAVA K P

Reputation: 33

Series with fractions in java

Refer 4th series for better clarificationI need to use loop to find the sum of the following series:

(2/3)-(4/5)+(6/7)-(8/9)+......±n

I have to use for-loop only for this program. Refer the code to see what I've done:

import java.util.Scanner;
public class P64 {
    public static void main(String args[]) {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter the limit");
        double n=sc.nextDouble();
        double sum=0;
        for(double i=1;i<=n;i++) {
            if(i%2==0)
            sum=sum-(++i/i++);
            else
            sum=sum+(++i/i++);
        }
            System.out.println(sum);
    }
}

I have tried this out but the output is either 1 or 0.

Upvotes: 2

Views: 1072

Answers (4)

duffymo
duffymo

Reputation: 308743

I think simpler is better.

Encapsulating it in a function makes your code easier to test and use outside the main method.

/**
 * @link https://stackoverflow.com/questions/58606895/series-with-fractions-in-java
 */
public class P64 {

    public static void main(String[] args) {
        int n = (args.length > 0) ? Integer.parseInt(args[0]) : 10;
        System.out.println(String.format("n: %5d sum: %10.5f", n, series(n)));
    }

    static double series(int n) {
        int sign = 1;
        double sum = 0.0;
        for (int i = 1; i <= n; ++i) {
            double x = 2.0*i;
            double term = sign*x/(x+1.0);
            sum += term;
            sign *= -1;
        }
        return sum;
    }
}

Upvotes: 0

Eritrean
Eritrean

Reputation: 16498

I would use a variable for the alternating +- and take a step of two at each iteration:

public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter the limit");
    double n = sc.nextDouble();
    double sum = 0;
    int sign = 1;
    for (double i = 2; i <= n; i = i+2 ) {
        sum = sum + (sign * (i/(i+1)));
        sign = -sign;
    }
    System.out.println(sum);
}

Upvotes: 2

Mustahsan
Mustahsan

Reputation: 3862

You should use a separate variable for values as using same in loop and your series will make it complex so, try this:

public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    System.out.println("Enter the limit");
    double n=sc.nextDouble();
    double sum=0;
    double j=1;
    for(double i=1;i<=n;i++)
    {
        if(i%2==0)
            sum=sum-(++j/++j);
        else
            sum=sum+(++j/++j);
    }
    System.out.println(sum);
}

Input: 4
Output: -0.16507936507936516

Upvotes: 2

Adder
Adder

Reputation: 5868

I removed the preincrement/postincrement trickery and made the limit determine the number of terms added up.

import java.util.Scanner;
public class P64
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter the limit");
        double n=sc.nextDouble();
        double sum=0;
        for(double i=1;i<=n;i++)
        {
            double delta = (2*i)/(2*i+1);
            if(i%2==0)
                sum -= delta;
            else
                sum += delta;
        }
        System.out.println(sum);
    }
}

Upvotes: 2

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