Recursion

Recursion is a technique in which a functions calls itself.

Factorial Example

Factorial is the multiplication of each numbers from 1 to N. For example 4 factorial = 4 * 3 * 2 * 1 = 24.

Let's look at the following example:

public class Main { public static void main(String[] args) { int factorial = calcFactorial(4); System.out.print(factorial); } static int calcFactorial(int num) { if (num == 0) { return 1; } return num * calcFactorial(num - 1); } }

Output:

24

At line 12 the function calls itself but with decremented value as argument.

The recursion should eventually end which is done at line 9.

Stack Overflow Exception

Recursion must have an end condition so an endless self calling is prevented.

If not stack overflow exception is thrown.

The following example causes such:

public class Main { public static void main(String[] args) { recursiveFunc(); // Causes exception. } static void recursiveFunc() { recursiveFunc(); } }