Array vs ArrayList: Choosing the Right Data Structure

This article aims to provide a comprehensive Array vs ArrayList comparison.

Array and ArrayList are fundamental data structures in Java used for storing and manipulating collections of elements. While they have similarities, they also differ in important ways.

Array vs ArrayList

Similarities between Array and ArrayList.

Let us look into similarities between Array and ArrayList

Element TypesBoth can store elements of any type.Both can store elements of any type.
Index AccessElements can be accessed by index.Elements can be accessed by index.
IterationBoth support iteration over elements.Both support iteration over elements.
Collection OperationsCommon operations such as adding, removing, and searching elements are supported.Common operations such as adding, removing, and searching elements are supported.
Memory EfficiencyBoth use contiguous memory locations to store elements.Both use contiguous memory locations to store elements.

Key Differences : Array vs ArrayList

Let’s look into Array vs ArrayList across different criteria.

ResizableArray is a fixed-length data structure.ArrayList is a resizable array.
Creating instance with/without specifying sizeIt is mandatory to provide the size of the Array while creating it.You can create an instance of ArrayList without specifying size, and Java will create it with a default size.
PrimitivesArray can contain both primitives and objects.ArrayList can only store objects, not primitives.
OperationsArrays do not have built-in functions for these operations.ArrayList supports additional operations like indexOf(), remove(), etc.
GenericsGenerics cannot be used with Array.ArrayList allows the use of Generics to ensure type-safety.
PerformanceArray operations like add() or get() have similar performance to ArrayList.ArrayList’s resize() operation can be slower as it involves creating a new Array and copying content.
Internal StructureArray is a basic data structure.ArrayList is internally backed by an Array.
LengthArray object has the length variable which returns the length of the array.Length of the ArrayList is provided by the size() method.
Multi-dimensionalYou can have a two-dimensional or a three-dimensional array.ArrayList doesn’t allow you to specify dimensions.
Adding elementsArray uses the assignment operator to store elements.Elements can be inserted into the ArrayList using the add() method.
FlexibilityArray is a fixed-length data structure.ArrayList is more flexible than a plain native array because it can grow dynamically when needed.
IterationArray can be iterated using for or for-each loops.ArrayList provides multiple ways for iteration, including for each loop, while loop, do-while loop, Iterator, and ListIterator.


Array vs ArrayList: Understanding the differences and considering the trade-offs allows developers to make informed decisions when selecting the appropriate data structure for their programs.

Also Read : ArrayList vs LinkedList

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