Question

How to measure the average performance of sorting algorithms with different sizes and numbers(with arrayList<Integer>) and compare with a graph?

I have these methods:

//This one receives one size(n) parameter

   public static ArrayList<Integer> RandomArray(int n){
      
       ArrayList<Integer> randomArray = new ArrayList<Integer>(n);
      
       Random rand = new Random(); //--- random number
       rand.setSeed(System.currentTimeMillis());
      
       for(int i = 0; i < n; i++ ) {
           //loop for creating random numbers until n size
           randomArray.add(i, Math.abs(rand.nextInt() % 256));
       }
       return randomArray;
   }

//I have this one to show the Array

   public static void ShowArray(ArrayList<Integer> array) {
      
       for(int arrayItem : array)
       {
       System.out.println(arrayItem);
       }

   }

//and this ones on my main

ArrayList<Integer> arrayShow = RandomArray(4); // this one to create an ArrayList and using the method RandomArray with the n Size.
       System.out.println(arrayShow);
      
       ArrayList<Integer> sortArrayA = new Sorting().SortX(arrayShow).;
       ArrayList<Integer> sortArrayB = new Sorting().SortY(arrayShow);
       ArrayList<Integer> sortArrayC = new Sorting().SortZ(arrayShow);

Now I have 3 sorting methods in a different file, how can I measure the performance of each algorithm, and compare? Where should I set a timer when I call each sort method, and should I create a loop to run like 5000 times so that I can compare?

Answer 1

Java has a API as

System.currentTimeMillis() which gives the current time in milliseconds and return type is long type.

So before calling you method in SortX(), You can do 
long start = System.currentTimeMillis();

and then you call your method as: ArrayList<Integer> sortArrayA = new Sorting().SortX(arrayShow);

Once your method call is done.. You again call long end = System.currentTimeMillis();

Now to get the elapsed time in Sorting, You can do (end - start) and that will be time used in milliseconds.
======

Regarding a loop for 5000 times, You can get the elapsed time in each cycle and then sum them up, and take the average elapsed time.. That way it will be more efficient. Let me know if any more help is needed on this. Thanks!