Fibonacci Series Java Program Using for Loop

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In this Java program, I show you how to calculate the Fibonacci series of a given number in Java (using for loop).
Fibonacci series is a sequence of values such that each number is the sum of the two preceding ones, starting from 0 and 1. The beginning of the sequence is thus:
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144 ...

Fibonacci Series Java Program Using for Loop

In this program, we are using a simple for loop to demonstrate how to calculate the Fibonacci series in Java.
package net.javaguides.corejava.programs;

import java.util.Scanner;

/**
 * This program calculates the fibonacci sequence of given number.
 * 
 * @author Ramesh Fadatare
 *
 */
public class FibonacciProgramUsingLoop {

 public static void main(String[] args) {

  Scanner scanner = new Scanner(System.in);

        System.out.print("Enter a number: ");

        int maxNumber = scanner.nextInt();
        
        int previousNumber = 0;
        int nextNumber = 1;

        System.out.print("Fibonacci Series of " + maxNumber + " numbers:");

        for (int i = 1; i <= maxNumber; ++i) {
             System.out.print(previousNumber + " ");
             int sum = previousNumber + nextNumber;
             previousNumber = nextNumber;
             nextNumber = sum;
        }
  
        scanner.close();
    }
}
Output:
Enter a number: 10

Fibonacci Series of 10 numbers:0 1 1 2 3 5 8 13 21 34

Fibonacci Series Java Program Using for Loop and BigInteger

Since Fibonacci series is a sequence of infinite numbers, we use BigInteger type for calculations:
package net.javaguides.corejava.programs;

import java.math.BigInteger;
import java.util.Scanner;

/**
 * This program calculates the fibonacci sequence of given number.
 * @author Ramesh Fadatare
 *
 */
public class FibonacciProgramUsingLoop {
 
 public static BigInteger fibonacci(int n) {

        if (n <= 1) return BigInteger.valueOf(n);

        BigInteger previous = BigInteger.ZERO, next = BigInteger.ONE, sum;

        for (int i = 2; i <= n; i++) {

            sum = previous;
            previous = next;
            next = sum.add(previous);
        }

        return next;
    }

    public static void main(String[] args) {

     Scanner scanner = new Scanner(System.in);

        System.out.print("Enter a number: ");

        int n = scanner.nextInt();
        
        for (int i = 0; i < n; i++) {

            BigInteger val = fibonacci(i);
            System.out.print(val + "\t");
        }
        
        scanner.close();
    }
}
Output:
Enter a number: 10

0 1 1 2 3 5 8 13 21 34

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