Java - Cannot call class cannot find symbol error

Question

UPDATE: It's still not working with:

List<Integer> mylist = new MyArrayList<>(); 

I'm having an issue with calling a class.

In the code, the mergeSort() is underline red and has the following error:

Cannot find symbol
symbol: method mergeSort(int,int)
location: variable mylist of type ArrayList<Integer>

I have tried declaring the ArrayList in the main file as an Object, or ElemType, but it doesn't fix the issue at all. Potentially, I think it could be an error with NetBeans.

I have also tried converting the Integer ArrayList to an Int ArrayList, i.e. myList[] = (values)

The main Java file is:

package testermergesort;

import java.util.*;

public class TesterMergeSort {

    public static void main(String[] args) {
        ArrayList<Integer> mylist = new ArrayList<Integer>();

        for(int i = 0; i < 100; i++)
        {
            int randomNum = (int) (Math.random()*1000);
            mylist.add(new Integer(randomNum));

        }

        //System.out.println(mylist.toString());

        int start = 0;
        int end = mylist.size() -1;


        mylist.mergeSort(start,end);
    }

}

And the classes file is:

package testermergesort;
import java.util.*;

public class MyArrayList<ElemType> extends ArrayList<ElemType>
{

    public void mergeSort(int start, int end)
    {   
        // use array,start,end if static only

        if (start < end){
            int mid = (start+end)/2;
            mergeSort(start, mid);
            mergeSort(mid+1, end);
            merge(start, mid, end);
        }
        else{
            return;
        }
     }


    public void merge (int left, int middle, int right)
    {
       ArrayList<Object> temp_array = new ArrayList<Object>();

       int i = left;
       int j = middle + 1;
       int k = 0;
       int pos;

        Comparable ElemAtI = (Comparable)get(i);
        Comparable ElemAtJ = (Comparable)get(j);
        Comparable ElemAtK = (Comparable)get(k);

//        Comparable temp_I = (Comparable)temp_array.get(i);
//        Comparable temp_J = (Comparable)temp_array.get(j);
//        Comparable temp_K = (Comparable)temp_array.get(k);

        while(i <= middle && j <= right)
        { 
            if(ElemAtI.compareTo(ElemAtJ) < 0)
            {
                temp_array.add(k,ElemAtI);
                i = i+1;
            }
            else{
                temp_array.add(k,ElemAtJ);
                j = j+1;
            }
            k = k+1;

        }

        while(i <= middle)
        {
            temp_array.add(k,ElemAtI);
            k = k+1;
            i = i+1;
        }
        while(j <= right)
        {
            temp_array.add(k,ElemAtJ);
            k = k+1;
            j = j+1;
        }

    for(i = left, k = 0; i <= right; i++, k++){
        set(i,(ElemType)temp_array.get(k));
        }



    }
}