Exception in thread "main" java.lang.StackOverflowError
- by Ray.R.Chua
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)
