Here is a classic recursive algorithm. The mathematical formula for factorial:
* 1!=1
* 2!=2 (2*1)
* 3!=6 (3*2*1)
* 4!=24 (4*3*2*1)
* 5!=120 (5*4*3*2*1)
* and so on
This can be described in pseudo-code as:
fact(x) ::= if ( x == 1 ) then 1 else x + fact(x-1)
In Java code it would look like this:
1 public int fact(int x) {
2 if ( x== 1 )
3 return 1;
4 else
5 return x * fact(x-1);
6 }
It is recursive because the function has a call to itself (see line 5). The most important part of creating a recursive algorithm is to determine the halt condition. In the case of the fact function the halt condition is when x==1. If you fail to code a halt condition (or if the condition has a bug) then you will likely run into a infinite loop which in Java would result in a StackOverflowError.
