Array Vs ArrayList performance test while adding and accessing elements

Question

I tried the following to test the performance of array and ArrayList. I know That arrayList is backed-up by array, but i saw strange behavior while accessing the data from list and array as mentioned below.. I would like to understand why this behavior? Doesn't the creating ArrayList with initial capacity improve performance, or am i doing any mistake?. I did not find any improvement on performance while adding the elements.

The output of below program is given below

time taken to add elements 1
time taken to print elements 229
LIST: time taken to add elements 10 // it is same even i set the initial capacity by passing as arg to constructor.
LIST: time taken to print elements 161

I have omitted the print statements as its taking space.

I see, its a duplicate post, however, posting as it is giving different behavior while retrieving.

package com.samples.misc;

import java.util.ArrayList;
import java.util.List;

public class ArrayTest {

    public static void main(String[] args) {

        long startTime = System.currentTimeMillis();
        int a[] = new int[50000];
        for(int i=0;i<a.length;i++)
            a[i] = i;
        long endTime = System.currentTimeMillis();
        System.out.print("time taken to add elements "+(endTime - startTime));
        System.out.println();

        startTime = System.currentTimeMillis();
        for(int i=0;i<a.length;i++)
            System.out.print(a[i]);
        endTime = System.currentTimeMillis();
        System.out.println();
        System.out.println("time taken to print elements "+(endTime - startTime));
        System.out.println();

        startTime = System.currentTimeMillis();
        List<Integer> integers = new ArrayList<Integer>(); 
        //List<Integer> integers = new ArrayList<Integer>(50000); this does not make any diff, it takes same amount of time to add elements, whats the use case of this?
        for(int i=0;i<50000;i++){
            integers.add(i);
        }
        endTime = System.currentTimeMillis();
        System.out.println("LIST: time taken to add elements "+(endTime - startTime));
        System.out.println();

        startTime = System.currentTimeMillis();
        for(int i=0;i<a.length;i++)
            System.out.print(integers.get(i));
        endTime = System.currentTimeMillis();
        System.out.println();
        System.out.println("LIST: time taken to print elements "+(endTime - startTime));
    }
}

Answer 1

it's not really a fair comparison as in the array you're adding int (primitive type) while in the list you're implicitly adding Integer (object), which are more heavyweight. A fair comparison would be Integer[] instead of int[]. Autoboxing will take care of the conversions so this is all you need to change to make for a valid comparison. Likely the print operation requires objects after all, so outputting the array requires more time there creating the objects, whereas the list already has them at that point.