A18 Merge

import java.util.*;
//Andy Zhang, 2
public class Merge
{
    public void merge(ArrayList <Integer> a, ArrayList <Integer> b, ArrayList <Integer> c)
    {
        if (a.size() == 0)
        {
            for (int x = 0; x < a.size(); x++)
            {
                c.add(a.get(x));
            }
        }
        else if (b.size() == 0)
        {
            for (int y = 0; y < b.size(); y++)
            {
                c.add(b.get(y));
            }
        }
        else
        {
            while (a.size() != 0 && b.size() != 0)
            {
                if (a.get(0) < b.get(0))
                {
                    c.add(a.get(0));
                    a.remove(0);
                }
                else
                {
                    c.add(b.get(0));
                    b.remove(0);
                }
            }
            if (a.size() == 0)
            {
                for (int x = 0; x < a.size(); x++)
                {
                    c.add(a.get(x));
                }
            }
            else if (b.size() == 0)
            {
                for (int y = 0; y < b.size(); y++)
                {
                    c.add(b.get(y));
                }
            }
        }
        screenOutput(c);
    }
    /**
     *  Initializes and returns temp with random integers in the range
     *  1 to largestInt
     *
     * @return  an ArrayList of size specified by the user filled
     *          with random numbers
     */
    public ArrayList <Integer> fillArray(int numInts, int largestInt)
    {
        Scanner console = new Scanner(System.in);
        System.out.println();
        System.out.print("How many numbers do you wish to generate? ");
        numInts = console.nextInt();
        ArrayList <Integer> temp = new ArrayList <Integer> ();
        System.out.print("Largest integer to generate? ");
        largestInt = console.nextInt();
        Random randGen = new Random();
        for (int loop = 0; loop < numInts; loop++)
        {
            temp.add(randGen.nextInt(largestInt) + 1);
        }
        return temp;
    }
    /**
     *  Prints out the contents of the array in tabular form, 20 columns
     */
    public void screenOutput(ArrayList <Integer> temp)
    {
        for (int loop = 0; loop < temp.size(); loop++)
        {
            if (loop % 15 == 0)
            {
                System.out.println();
            }
            System.out.printf("%5d",temp.get(loop));
        }
        System.out.println();
    }
    public ArrayList <Integer> insertionSort(ArrayList <Integer> list)
    {
        for (int outer = 1; outer < list.size(); outer++){
            int position = outer;
            int key = list.get(position);

            // Shift larger values to the right
            while (position > 0 && list.get(position - 1) > key){
                list.set(position, list.get(position - 1));
                position--;
            }
            list.set(position, key);
        }
        return list;
    }
    public void mergeRun()
    {
        ArrayList <Integer> empty = new ArrayList <Integer> ();
        merge(insertionSort(fillArray(20, 100)), insertionSort(fillArray(40, 100)), empty);
    }
}