Arrays vs ArrayLists

Both Arrays and ArrayLists are incredibly useful to programmers, but how do we know when to use them? While both Arrays and ArrayLists perform similar operations, they are used differently.

Differences Between Arrays and ArrayLists

One the biggest differences between an Array and ArrayList is expandability. While the size of an ArrayList can change, an Array is a set size. Other differences include handling types and getting the size/length.

Getting the Size or Length:

How we retrieve the size or length of an Array or ArrayList varies between the two.

When dealing with an Array we use arr.length to access its length.

With ArrayLists we would use list.size().

Setting Values at an Index:

Settings values at a given index varies as well.

To set the value of a given index with an Array we use arr[i] = x;.

To set the value of a given index with an ArrayList we use list.set(i, x);.

Getting Values at an Index:

To retrieve values at a given index is as follows:

To get a value at a given index with an Array we use int x = arr[i];.

To get a value at a given index with an ArrayList we use int x = list.get(i);.

Creating New Instances:

To create new instances of an Array or ArrayList you use:

To create a new instance of an Array we use int[] arr = new int[5];.

To create a new instance of an ArrayList we use

ArrayList<Integer> list = new ArrayList<Integer>();

Extra Helper Methods:

Only ArrayLists have extra helper methods. These helper methods include: remove, add at index, clear, and isEmpty.

Types:

Arrays can hold Primitives or Objects.

ArrayLists can only hold Objects, and handles autoboxing and unboxing.