Fibonacci Sequence : Sum of all numbers

Question

I am new to Java and this is what I have to do:

The sequence goes as follows: 1, 1, 2, 3, 5, 8, 13, 21, .... Etc.

The next number in the sequence is the sum of the previous 2 number

Write a program that lets the user input a number, n, and then calculates the nth number of the sequence and the sum of the numbers in the sequence.

For Example, the 5th number is 5 and the sum up to that number is 12

This is not a duplicate as my question is different from the rest and my code is also different. Here is what I have done so far:

public class fibonnacifinal {

    public static void main(String args[]) {
        System.out.println("Enter number upto which Fibonacci series to print: ");
        int number = new Scanner(System.in).nextInt();
        System.out.println("\n Fibonacci number at location " + number + " is ==> " + (fibonacciLoop(number) + ""));
    }

    public static int fibonacciLoop(int number) {
        if (number == 1 || number == 2) {
            return 1;
        }

        int fibo1 = 1, fibo2 = 1, fibonacci = 1;
        for (int i = 3; i <= number; i++) {
            fibonacci = fibo1 + fibo2; // Fibonacci number is sum of previous two Fibonacci number
            fibo1 = fibo2;
            fibo2 = fibonacci; 
        }
        return fibonacci; // Fibonacci number
    }
}

The problem I am having is that I cannot get the numbers to add and print. For example, if user inputs 7, I can get it to say that 7th number is 13 but I cant get it to print that sum upto that number is 33.

Answer 1

As you are starting from i = 3 you can use the following inside your fibonacciLoop(int number):

int sum = 2;
for (int i = 3; i <= number; i++) {
    fibonacci = fibo1 + fibo2; 
    fibo1 = fibo2;
    fibo2 = fibonacci;
    sum = sum + fibonacci;
}
System.out.println("Sum: " +sum); //print before return fibonacci

Note, soon int sum will overflow for large fibonacci number.

Here is a full functional code for you!

Answer 2

you just need to sum the result of each fibonacci

    public class Fibonnacifinal {
        public static void main(String args[]) {
            System.out
                    .println("Enter number upto which Fibonacci series to print: ");
            int number = new Scanner(System.in).nextInt();
            System.out.println("\n Sum of Fibonacci numbers at location " + number
                    + " is ==> " + (fibonacciLoop(number) + ""));
        }

        public static int fibonacciLoop(int number) {
            // Fib(1) = 1, returns 1
            // Fib(2) = 2, returns 2 which is the sum of Fib(1) + Fib(1)
            if (number < 3) {
                return number;
            }

            int sum = 2; // 2 is the sum till Fib(2)
            int fibo1 = 1, fibo2 = 1, fibonacci = 1;
            for (int i = 3; i <= number; i++) {
                fibonacci = fibo1 + fibo2;
                sum += fibonacci;
                fibo1 = fibo2;
                fibo2 = fibonacci;
            }

            return sum;
        }

    }

Answer 3

You already return the Fibonacci number.

If you want to return both: Fibonacci number + the sum, you need to change the method type to a pair.

If you just want to print the sum, add the following lines in that method:

public static int fibonacciLoop(int number) {
    int sum = 0;
    if (number == 1) { // 1
        System.out.println("1");
    } else if (number == 2) { // 1, 1
        System.out.println("2");
    } else {
        sum = 2;
    }
    ...
    for (int i = 3; i <= number; i++) {
        ...
        sum += fibonacci;
    }
    System.out.println(sum);
    ...
}