Recursion

Question

Please explain how it work? http://www.sololearn.com/app/java/playground/c4NJ2Nr8h51B/

Answer 1

import java.util.LinkedList;

public class MyClass {
public static void main(String[ ] args) {

printNum(5);
}

public static void printNum(int n){
if(n==1) {
System.out.println(n);
}else{
printNum (n-1);
System.out.println(n);

}
}
}

This application starts with printNum with value 5. Let's trace the function.

there is a condition statement.
If 5==1 False
Else //here

in else bracket, printNum (4) is called.

Then let's start printNum with value 4.
if 4==1 False
Else //Again here.

...

then you'll reach at printNum (1).

If 1==1 True
Yeah!
then program prints out 1. (value of n)

then this function ends.

In printNum (2),
Else
printNum (1) was done.
So next statement works.
This prints out 2 (value of n)

Again, this function of printNum (2) finishes, system reads next line of printNum (3), which called printNum (2) in Else.

...

Therefore the result is
1
2
3
4
5

Answer 2

Thanks @kimminkwan