Review recursion

 Today, encounter an recursion problem to caculate the sum value of 1+2+3...+100.

 

So simple question, eventhough I can finish the program. However, I am not very clear about the concept of recursion. Record it now:

 

 

my code:

public class Recursion{public int sumVar = 0;public int i = 0;public int sum(int sumVar, int i){ if(i < 101) { return sum(sumVar+i++,i++); } return sumVar;}public static void main(String args[]){ Recursion rec = new Recursion(); System.out.println(rec.sum(rec.sumVar,rec.i));}}

 

In fact,

 

the concept of recursion is a method of defining functions in which the function being defined is applied within its own definition.

 

such as following function:

 

if n =1,  fun(n) = 1;   if n > 1, fun(n)=fun(n-1).