I have a piece of code and I could not figure out why it is giving me Exception in thread "main" java.lang.StackOverflowError.

This is the question:

Given a positive integer n, prints out the sum of the lengths of the Syracuse 
sequence starting in the range of 1 to n inclusive. So, for example, the call:
lengths(3)
will return the the combined length of the sequences:
1
2 1
3 10 5 16 8 4 2 1 
which is the value: 11. lengths must throw an IllegalArgumentException if 
its input value is less than one.

My Code:

import java.util.HashMap;

public class Test {

HashMap<Integer,Integer> syraSumHashTable = new HashMap<Integer,Integer>();

public Test(){

}

public int lengths(int n)throws IllegalArgumentException{

    int sum =0;

    if(n < 1){
        throw new IllegalArgumentException("Error!! Invalid Input!");
    }   

    else{


        for(int i =1; i<=n;i++){

            if(syraSumHashTable.get(i)==null)
            {
                syraSumHashTable.put(i, printSyra(i,1));
                sum += (Integer)syraSumHashTable.get(i);

            }

            else{

                sum += (Integer)syraSumHashTable.get(i);
            }



        }

        return sum;

    }



}

private int printSyra(int num, int count){

    int n = num;

    if(n == 1){

        return count;
    }

    else{   
            if(n%2==0){

                return printSyra(n/2, ++count);
            }

            else{

                return printSyra((n*3)+1, ++count) ;

            }

    }


}
}

Driver code:

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Test s1 = new Test();
    System.out.println(s1.lengths(90090249));
    //System.out.println(s1.lengths(5));
}

. I know the problem lies with the recursion. The error does not occur if the input is a small value, example: 5. But when the number is huge, like 90090249, I got the Exception in thread "main" java.lang.StackOverflowError. Thanks all for your help. :)

I almost forgot the error msg:

Exception in thread "main" java.lang.StackOverflowError
at Test.printSyra(Test.java:60)
at Test.printSyra(Test.java:65)
at Test.printSyra(Test.java:60)
at Test.printSyra(Test.java:65)
at Test.printSyra(Test.java:60)
at Test.printSyra(Test.java:60)
at Test.printSyra(Test.java:60)
at Test.printSyra(Test.java:60)