public class CollatzProblem {

            public static void main(String[] args) {
                    // This is the number the program will go up to, so to find maximum from 1 to 100, we make k = 100
                    double k = 1000000;
                    // An array to keep track of the values we get
                    double[] length = new double[(int)k];

                    // Loop through all possible starting values, from 1 to 'k'
                    for(double start = 1; start < k; ++start){
                            double current = start;
                            double count = 0;

                            // This is where iteration happens, we keep iterating until we get a '1'
                            // While doing so it counts each iteration
                            while(current != 1){
                                    current = iterate(current); // See next method to see how it iterates
                                    ++count;
                            }

                            length[(int)start] = count;

                    }
                    // This will find the actual maximum value in the array
                    double max = length[0];

                    for(double i=0; i< k; ++i){
                            if(max < length[(int)i]){
                                    max = length[(int)i];
                            }
                    }
                    // This will find the value that belongs to this 'max', this is the value we want
                    double maxIndex = 0;

                    for(double i=0; i<k; ++i){
                            if(max == length[(int)i]){
                                    maxIndex = i;
                            }
                    }

                    System.out.println("Index: " + maxIndex + " Amount: " + max);

            }

            public static double iterate(double n){
                    // Do as the function says, if n is even, halve it, if n is odd, 3*n+1 is output
                    double out = 0;

                    if(n%2 == 0){
                            out = n/2;
                    }
                    if(n%2 != 0){
                            out = 3*n+1;
                    }
                    return out;
            }

    }