Java Program to Print Fibonacci Series

You can print the Fibonacci series in Java by using a loop to add the last two numbers starting with 0 and 1, like this: int a=0, b=1; for(int i=0; i.

Examples

Input5

Output0 1 1 2 3

Input1

Output0

Input0

Output

How to Think About It

To print the Fibonacci series, start with the first two numbers 0 and 1. Then, keep adding the last two numbers to get the next one. Repeat this process until you have printed the desired count of numbers.

Algorithm

1

Get the number of terms to print (n).

2

Initialize two variables with 0 and 1 as the first two Fibonacci numbers.

3

Use a loop to repeat n times:

4

Print the current number.

5

Calculate the next number by adding the previous two.

6

Update the variables to move forward in the series.

Code

java

public class Fibonacci {
    public static void main(String[] args) {
        int n = 10; // number of terms
        int a = 0, b = 1;
        for (int i = 0; i < n; i++) {
            System.out.print(a + " ");
            int c = a + b;
            a = b;
            b = c;
        }
    }
}

Output

0 1 1 2 3 5 8 13 21 34 

Dry Run

Let's trace printing 5 Fibonacci numbers through the code

1

Initialize variables

a=0, b=1

2

Iteration 1

Print a=0; c=0+1=1; a=1; b=1

3

Iteration 2

Print a=1; c=1+1=2; a=1; b=2

4

Iteration 3

Print a=1; c=1+2=3; a=2; b=3

5

Iteration 4

Print a=2; c=2+3=5; a=3; b=5

6

Iteration 5

Print a=3; c=3+5=8; a=5; b=8

Iteration	a (printed)	b	c (next)
1	0	1	1
2	1	1	2
3	1	2	3
4	2	3	5
5	3	5	8

Why This Works

Step 1: Start with first two numbers

The Fibonacci series always begins with 0 and 1, so we set a=0 and b=1.

Step 2: Print current number

In each loop iteration, we print the current number stored in a.

Step 3: Calculate next number

We find the next Fibonacci number by adding a and b, then update a and b to move forward.

Alternative Approaches

Recursive method

java

public class Fibonacci {
    public static int fib(int n) {
        if (n <= 1) return n;
        return fib(n-1) + fib(n-2);
    }
    public static void main(String[] args) {
        int n = 10;
        for (int i = 0; i < n; i++) {
            System.out.print(fib(i) + " ");
        }
    }
}

This method is simple but inefficient for large n because it recalculates values many times.

Using array to store series

java

public class Fibonacci {
    public static void main(String[] args) {
        int n = 10;
        int[] fib = new int[n];
        fib[0] = 0;
        fib[1] = 1;
        for (int i = 2; i < n; i++) {
            fib[i] = fib[i-1] + fib[i-2];
        }
        for (int i = 0; i < n; i++) {
            System.out.print(fib[i] + " ");
        }
    }
}

This stores all Fibonacci numbers but uses extra memory.

Complexity: O(n) time, O(1) space

Time Complexity

The loop runs n times, so the time grows linearly with the number of terms.

Space Complexity

Only a few variables are used, so space is constant regardless of n.

Which Approach is Fastest?

The iterative loop method is fastest and most memory-efficient compared to recursion or array storage.

Approach	Time	Space	Best For
Iterative loop	O(n)	O(1)	Large n, efficient
Recursive method	O(2^n)	O(n)	Small n, simple code
Array storage	O(n)	O(n)	When all values needed later