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Java Program to Display Fibonacci Series

## Display Fibonacci Series

The Fibonacci series is a series where the next term is the sum of the previous two terms. The first two terms of the Fibonacci sequence are 0 followed by 1.

Fibonacci Series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34

Suppose, our first two terms are:

first = 0 second = 1

The next terms in the Fibonacci series would be calculated as:

nextTerm = first + second; (0 + 1) first = second; (1) second = nextTerm; (1) nextTerm = first + second; (1 + 1)

Let's now apply this logic to our program.

### Example: Display Fibonacci Series Using for Loop

class Main { public static void main(String[] args) { int n = 10, first = 0, second = 1; System.out.println("Fibonacci Series till " + n + " terms:"); for (int i = 1; i <= n; ++i) { System.out.print(first + ", "); // compute the next term int nextTerm = first + second; first = second; second = nextTerm; } } }

Output

Fibonacci Series till 10 terms: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34,

In the above program, `first` and `second` are initialized with 0 and 1 respectively (first two digits of the Fibonacci series).

Here, we have used the `for`

loop to

- print the
`first`of the series - compute
`nextTerm`by adding`first`and`second` - assign value of
`second`to`first`and`nextTerm`to`second`

### Display the Fibonacci series up to a given number

class Fibonacci { public static void main(String[] args) { int n = 100, first = 0, second = 1; System.out.println("Fibonacci Series Upto " + n + ": "); while (first <= n) { System.out.print(first + ", "); int nextTerm = first + second; first = second; second = nextTerm; } } }

Output

Fibonacci Series Upto 100: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89,

In this example, instead of displaying the Fibonacci series of a certain number, we are displaying the series up to the given number (100).

For this, we just need to compare the `first` with `n`. And, if `first` is less than `n`, it is printed in the series. Else, the series is completed.

We can also use a `while`

loop to generate the Fibonacci series in Java.

### Display the Fibonacci series using a while loop

class Main { public static void main(String[] args) { int i = 1, n = 10, first = 0, second = 1; System.out.println("Fibonacci Series till " + n + " terms:"); while (i <= n) { System.out.print(first + ", "); int nextTerm = first + second; first = second; second = nextTerm; i++; } } }

Output

Fibonacci Series till 10 terms: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34,

The working of this program is the same as the previous program.

And, though both programs are technically correct, it is better to use a `for`

loop in this case. It's because the number of iterations (from 1 to `n`) is known.