In this Java program, we will learn how to print the Fibonacci series using both a traditional Java approach and Java 8 features.

The Fibonacci series is a sequence in which each number is the sum of the previous two numbers.

For example:

0 1 1 2 3 5 8 13 21 34

1. Normal Java Program

import java.util.Scanner;

public class FibonacciSeries {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the number of terms: ");
        int n = sc.nextInt();
        int first = 0;
        int second = 1;
        System.out.println("Fibonacci Series:");
        for (int i = 1; i <= n; i++) {
            System.out.print(first + " ");
            int next = first + second;
            first = second;
            second = next;
        }
        sc.close();
    }
}

Output

Enter the number of terms: 10
Fibonacci Series:
0 1 1 2 3 5 8 13 21 34

Explanation

The program starts with two numbers:

int first = 0;
int second = 1;

Inside the for loop, the next Fibonacci number is calculated by adding the previous two numbers:

int next = first + second;

The values are then updated:

first = second;
second = next;

This process continues until the requested number of terms is printed.

2. Java 8 Program to Print Fibonacci Series

Java 8 introduced the Stream API, which can be used to generate a Fibonacci series in a more functional programming style.

import java.util.Scanner;
import java.util.stream.Stream;

public class FibonacciJava8 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the number of terms: ");
        int n = sc.nextInt();
        System.out.println("Fibonacci Series:");
        Stream.iterate(
                new long[]{0, 1},
                f -> new long[]{f[1], f[0] + f[1]}
        )
        .limit(n)
        .forEach(f -> System.out.print(f[0] + " "));
        sc.close();
    }
}

Output

Enter the number of terms: 10
Fibonacci Series:
0 1 1 2 3 5 8 13 21 34

Explanation of Java 8 Program

The Java 8 version uses Stream.iterate() to generate Fibonacci numbers.

Stream.iterate(
    new long[]{0, 1},
    f -> new long[]{f[1], f[0] + f[1]}
)

The array stores two consecutive Fibonacci numbers.

For every iteration:

• The first value becomes the second value.
• The second value becomes the sum of the two previous values.

The limit(n) method controls how many Fibonacci terms are generated:

.limit(n)

Finally, forEach() prints each generated value:

.forEach(f -> System.out.print(f[0] + " "));

Here, f -> is a Java 8 lambda expression.

Difference Between Normal Java and Java 8

Which Approach Should You Use?

For beginners and general-purpose Java programming, the normal for loop approach is recommended because it is easier to understand and maintain.

The Java 8 version is useful for learning how the Stream API and lambda expressions can be applied to sequence generation.

Conclusion

The Fibonacci series is a common Java programming problem used in coding interviews and programming exercises. The traditional approach uses a loop and variables, while the Java 8 approach demonstrates how Streams and Lambda expressions can generate the same sequence.