Sort.java

package multithreadedmergesort;

/**
 *
 * @author Davidthefat
 */
public class Sort extends Thread
{
    private static String[] nums;
    private static String[] temp; //Took the declaration out here
    private static int num;

    public Sort(String[] m)
    {
        nums = m;
        num = nums.length;
        temp = new String[num];//Constructed it here
        this.setName("Sort");
    }
    @Override
    public void run()
    {
        mergesort(0, num - 1, 2);
        temp = null;
    }
    public static void mergesort(int l, int h, int i)
    {
        if (l < h)
        {
            int m = (l + h) / 2;
            if(i > 0)
            {
                merger t1 = new merger(l, m, i - 1);
                merger t2 = new merger(m + 1, h, i - 1);
                t1.start();
                t2.start();
                try
                {
                    t1.join();
                    t2.join();
                }
                catch(InterruptedException e)
                {
                    System.out.println(e.getMessage());
                }
            }
            else
            {
                mergesort(l, m, 0);
                mergesort(m + 1, h, 0);
            }
            merge(l, m, h);
        }
    }
    private static void merge(int l, int m, int h)
    {
        System.arraycopy(nums, l, temp, l, h - l + 1);
        int i = l;
        int j = m + 1;
        int k = l;
        while (i <= m && j <= h)
        {
                if (temp[i].compareTo(temp[j]) < 0)
                {
                        nums[k] = temp[i];
                        i++;
                }
                else
                {
                        nums[k] = temp[j];
                        j++;
                }
                k++;
        }
        while (i <= m)
        {
                nums[k] = temp[i];
                k++;
                i++;
        }
    }
}
class merger extends Thread
{
    private int l;
    private int h;
    private int i;
    public merger(int lo, int hi, int in)
    {
        l = lo;
        h = hi;
        i = in;
        this.setName("merger " + in);
    }
    @Override
    public void run()
    {
        Sort.mergesort(l, h, i);
    }
}