# Factorial of a Number in Java

## Factorial of a Number in Java

Here on this page, we will learn how to Find the Factorial of a Number in Java. Factorial is a sequence of a number where we multiply by all previous numbers.

``````factorial of n (n!) = 1 * 2 * 3 * 4....n

Note : 0! = 1 and 1! = 1

Example :
5! = 1 * 2 * 3 * 4 * 5 = 120``````

### Methods we will discuss

• Iterative approach for factorial
• Recursive approach for factorial

### Method 1

For an input num

• Initialize fact = 1
• If num < 0 : Print Error as we can’t calculate factorial of a negative number
• Else run a iterative loop in iteration of (i) between [1, num]
• do fact = fact * i
• print the value of fact

### Java Code

Run
```class Main
{
// Method to find factorial of the given number
static int factorial(int n)
{
int res = 1, i;
for (i = 2; i <= n; i++)
res *= i;
return res;
}

// Driver method
public static void main(String[] args)
{
int num = 6;
System.out.println("Factorial of " + num + " is " + factorial(num));
}
}
```

### Output:

`Factorial of 6 is 720`

### Method 2

This method uses the recursive approach, for input num

For an input num

• Call function getFactorial(num)
• Set base case when num== 0 return 1
• Other cases return num * getFactorial(num-1);

### Java Code

Run
```class Main
{
// method to find factorial of given number
static int factorial(int n)
{
if (n == 0)
return 1;
return n * factorial(n - 1);
}

// Driver method
public static void main(String[] args)
{
int num = 6;
System.out.println("Factorial of " + num + " is " + factorial(num));
}
}```

### Output:

`Factorial of 6 is 720`

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