public class ProjectEuler14
{
    public static void main(String[] args)
    {
        final double TIME_START = System.currentTimeMillis();

        Collatz c = new Collatz();
        int highestNumOfTerms = 0;
        int currentNumOfTerms = 0;
        int highestValue = 0; //Value which produces most number of Collatz terms


        for (double i = 1.; i <= 1000000.; i++)
        {
            currentNumOfTerms = c.startCollatz(i);


            if (currentNumOfTerms > highestNumOfTerms)
            {
                highestNumOfTerms = currentNumOfTerms;
                highestValue = (int)(i);
                System.out.println("New term: " + highestValue);
            }
        }

        final double TIME_STOP = System.currentTimeMillis();

        System.out.println("Highest term: " + highestValue + " with " + highestNumOfTerms + " number of terms");
        System.out.println("Completed in " + ((TIME_STOP - TIME_START)/1000) + " s");
    }
}


public class Collatz
{
    private static int numOfTerms = 0;
    private boolean isFirstRun = false;

    public int startCollatz(double n)
    {
        isFirstRun = true;
        runCollatz(n);
        return numOfTerms;
    }

    private void runCollatz(double n)
    {
        if (isFirstRun)
        {
            numOfTerms = 0;
            isFirstRun = false;
        }

        if (n == 1)
        {
            //Do Nothing
            //Causes return to startCollatz()
        }

        else if (n % 2 == 0)
        {
            //Divides n by 2 following Collatz rule, running recursion
            numOfTerms = numOfTerms + 1;
            runCollatz(n / 2);
        }

        else if (n % 2 == 1)
        {
            //Multiples n by 3 and adds one, following Collatz rule, running recursion
            numOfTerms = numOfTerms + 1;
            runCollatz((3 * n) + 1);
        }
    }
}