Code works when I step through it, not when run real-time though.

Question

Hi,
I have a bit of code, a trivial problem in fact, that has completely defeated me.
private int recFibonacci(int N, long starTime) {
        long totalTime = System.currentTimeMillis() - starTime;
        if(N <= 0) return -3;  //negatives not allowed
        try {
            if (N < 2) {
                return N;
            } else {
                if (totalTime <= 1500) { //if it takes longer than 15 seconds, end.
                    N = recFibonacci(N - 2, starTime) + recFibonacci(N - 1, starTime);
                } else {
                    return -1;//return if taking too long
        } catch (StackOverflowError ex) {
            return -2;//return if overflow
        return N;
//This is the user accessible function for the recursive fibonacci method.
//It calls the private fibonacci function and passes it a startTime value.
//This is so that the startTime is only set at the user's call, not each time the
//function recurses.
    public int recFibonacci(int N) {
        setTime();
        int retN = this.recFibonacci(N, getStartTime());
        if (retN == -1) {
            System.out.println("Calculation is is taking too long, try a non-recursive solution.");
            return -1;
        if (retN == -2) {
            System.out.println("Stack overflow, recursed too deeply.  Try a non-recursive solution, or a smaller number.");
            return -2;
        if (retN == -3){
            System.out.println("Fibonacci sequence is undefined for negative numbers.");
            return -3;
        return retN;
    }From the driver I call the single argument method.
When I debug and step through the code it runs perfectly. If the number is large enough to take a little while to execute,i get the appropriate error message. Also, if the number causes a stack overflow, I get that message as well.
When I run the code (realtime not stepping) I always get a strange return value if N is too large. Its always a different value, and I never receive the error code. I am at a complete loss to explain this discrepency.
Any ideas?

Answer 1

Seems to me your problem could be the same as this poster's:
[Problem With Recursion|http://forum.java.sun.com/thread.jspa?threadID=5270481]
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