Generate Fibonacci Sequence in Java: For, While, and Recursive Examples

What Is the Fibonacci Series in Java?

The Fibonacci series is a sequence where each number equals the sum of the two preceding ones. In Java, the series traditionally starts with 0 and 1:

0, 1, 1, 2, 3, 5, 8, 13, 21, …

Beyond its mathematical intrigue, the Fibonacci sequence is frequently used in algorithm analysis—for instance, in estimating the runtime of recursive procedures and in computing the greatest common divisor.

• For‑loop implementation
• While‑loop implementation
• Recursive implementation
• Interactive input example

Fibonacci Series Using a For Loop

// Using a for loop
public class FibonacciExample {
    public static void main(String[] args) {
        int maxNumber = 10;          // Number of terms
        int previous = 0;
        int current = 1;
        System.out.print("Fibonacci Series of " + maxNumber + " numbers:");
        for (int i = 1; i <= maxNumber; i++) {
            System.out.print(previous + " ");
            int next = previous + current;
            previous = current;
            current = next;
        }
    }
}

Output:

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

Logic:

• Initialize previous = 0 and current = 1.
• Loop maxNumber times, printing previous and updating values.

Fibonacci Series Using a While Loop

// Using a while loop
public class FibonacciWhileExample {
    public static void main(String[] args) {
        int maxNumber = 10;
        int previous = 0;
        int current = 1;
        System.out.print("Fibonacci Series of " + maxNumber + " numbers:");
        int i = 1;
        while (i <= maxNumber) {
            System.out.print(previous + " ");
            int next = previous + current;
            previous = current;
            current = next;
            i++;
        }
    }
}

Output:

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

Fibonacci Series Based on User Input

import java.util.Scanner;
public class FibonacciUserInput {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter the number of terms: ");
        int maxNumber = scanner.nextInt();
        int previous = 0;
        int current = 1;
        System.out.print("Fibonacci Series of " + maxNumber + " numbers:");
        for (int i = 1; i <= maxNumber; i++) {
            System.out.print(previous + " ");
            int next = previous + current;
            previous = current;
            current = next;
        }
        scanner.close();
    }
}

Logic: The same iterative logic applies, but the term count is supplied by the user.

Fibonacci Series Using Recursion

// Recursive implementation
public class FibonacciRecursion {
    public static int fibonacci(int n) {
        if (n == 0) return 0;
        if (n == 1 || n == 2) return 1;
        return fibonacci(n - 1) + fibonacci(n - 2);
    }
    public static void main(String[] args) {
        int maxNumber = 10;
        System.out.print("Fibonacci Series of " + maxNumber + " numbers: ");
        for (int i = 0; i < maxNumber; i++) {
            System.out.print(fibonacci(i) + " ");
        }
    }
}

Output:

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

Recursion Explained:

1. Base cases: n == 0 returns 0; n == 1 || n == 2 returns 1.
2. Recursive case: fibonacci(n) = fibonacci(n-1) + fibonacci(n-2).
3. Each call splits into two sub‑calls, mirroring the classic definition.

While recursion offers a clean mathematical expression, it incurs exponential time for large n. Use memoization or iterative methods for performance‑critical code.