Array vs. ArrayList — What's the Difference?
By Tayyaba Rehman — Published on January 29, 2024
An Array is a fixed-size collection of elements of the same type, while an ArrayList in languages like Java is a resizable array-like structure allowing elements to be added or removed.
Difference Between Array and ArrayList
Table of Contents
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Key Differences
An Array is a basic data structure in programming that holds a fixed number of values of the same data type. Once an array's size is defined, it cannot be changed, making arrays efficient but inflexible. In contrast, an ArrayList, as implemented in Java, is a part of the Java Collections Framework, offering an array-like structure that is dynamic and can resize itself as needed.
Arrays are generally faster and require less memory overhead compared to ArrayLists, as they have a fixed size and don't require additional memory for resizing operations. ArrayLists, however, are more flexible in managing data, allowing for easy insertion and removal of elements, which can be costly operations in arrays due to the need to shift elements.
When it comes to functionality, an Array is simple and straightforward with basic operations like accessing and setting elements by index. ArrayLists provide more advanced functionalities, including methods for searching, sorting, and manipulating the list of elements.
Type safety is another difference. Arrays are type-safe, meaning they can only store elements of a specified data type. ArrayLists can store objects of any type, but generic programming in languages like Java allows ArrayLists to be type-safe as well, by specifying the type of elements they can hold.
Initialization of an Array is done by specifying the number of elements it can hold, and it cannot grow or shrink. ArrayLists, however, start with an initial capacity and grow automatically when more elements are added, making them more versatile for situations where the number of elements can vary widely.
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Comparison Chart
Size Flexibility
Fixed size
Resizable
Memory Efficiency
More efficient (less overhead)
Less efficient (more overhead)
Functionality
Basic (access, set by index)
Advanced (add, remove, sort, etc.)
Type Safety
Type-safe
Can be type-safe with generics
Initialization
Size specified at creation
Grows dynamically
Compare with Definitions
Array
Efficient in memory usage due to its unchangeable size.
We used an array for our data as its size was constant.
ArrayList
A resizable array-like structure in Java.
The ArrayList dynamically adjusted its size as we added more elements.
Array
Elements are accessed and set by their index.
The value at index 3 in the array was updated.
ArrayList
Has an initial capacity that grows as needed.
The ArrayList started with 10 elements and expanded as more were added.
Array
Cannot be resized after creation.
We couldn't add more elements to the array as it was full.
ArrayList
Allows elements to be added or removed.
We removed an element from the ArrayList using its remove method.
Array
Type-safe and holds a specific data type.
The string array stores only text values.
ArrayList
Offers advanced functionalities like sorting and searching.
We used the sort method to order the elements in the ArrayList.
Array
To set out for display or use; place in an orderly arrangement
Arrayed the whole regiment on the parade ground.
ArrayList
Can be type-safe with the use of generics.
Our ArrayList only accepts string elements.
Array
A rectangular arrangement of quantities in rows and columns, as in a matrix.
Array
Numerical data linearly ordered by magnitude.
Array
An arrangement of usually identical devices, often sensors, that function as a unit
An array of solar panels.
Array
(Computers) A group of memory elements accessed by one or more indices.
Array
(programming) Any of various data structures designed to hold multiple elements of the same type; especially, a data structure that holds these elements in adjacent memory locations so that they may be retrieved using numeric indices.
Array
An orderly arrangement;
An array of troops in battle order
Array
An arrangement of aerials spaced to give desired directional characteristics
Array
A fixed-size collection of elements of the same type.
The array of integers had 10 elements.
Common Curiosities
What is an ArrayList?
An ArrayList is a dynamic, resizable array-like structure in Java.
What is an Array?
An array is a fixed-size data structure that holds elements of the same type.
Can ArrayLists store different types of elements?
Without generics, yes, but using generics can restrict them to a specific type.
How do you initialize an ArrayList in Java?
By using new ArrayList<>(), optionally specifying an initial capacity.
Are Arrays type-safe?
Yes, arrays can only store elements of a specified data type.
Is memory allocation different for Array and ArrayList?
Yes, arrays allocate memory for a fixed number of elements, while ArrayLists allocate additional memory to accommodate more elements.
Can an Array size change after creation?
No, an array’s size is fixed upon its creation.
How does an ArrayList resize itself?
It automatically increases its capacity when more elements are added beyond its initial size.
Can you add elements to an Array?
No, you cannot add elements to an array once it is created.
Why use an Array over an ArrayList?
Use an array for efficiency and when the number of elements is known and constant.
How do you remove an element from an ArrayList?
By using the remove(index) or remove(object) method.
Can Arrays hold primitive types?
Yes, arrays can hold both primitive types and objects.
How do you access elements in an ArrayList?
Elements in an ArrayList can be accessed using the get(index) method.
Are ArrayLists available in all programming languages?
No, ArrayLists are specific to certain languages like Java, but similar structures exist in other languages.
Which is faster, Array or ArrayList?
Arrays are generally faster due to their fixed size and direct access to elements.
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Written by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
