Difference Between Array and ArrayList In Java

April 22, 2023

What is Array and Array List In Java?

The Difference Between Array and ArrayList In Java where Array is a group of items of the same type that are stored together in a single memory location. Each item can be accessed by its position number, which starts from 0 and goes up to the total number of items minus one.

An ArrayList is a type of data structure in Java that can change its size based on the number of elements it holds. It is built as an array that can be resized, allowing you to add or remove items at any position in the list. The Java Collections Framework includes many helpful methods for managing the items in an ArrayList.

To Understand the Difference Between Array and ArrayList In Java, Read The Complete Article.

Methods of Creating Array

Declaring an array with a specified size and initializing its elements:
Declaring and initializing an array in one line:
Creating a copy of an existing array:
Using the Arrays.fill() method to initialize all elements of an array to a specified value:
Declaring and initializing a multi-dimensional array:

syntax for creating an Array in Java

datatype[] arrayName = new datatype[arraySize];

Java Array

Arrays have a fixed size and cannot be resized dynamically. Elements in an array are stored in contiguous memory locations, which can make access faster.

Arrays can be more memory-efficient than ArrayLists since they do not require the additional overhead of an object.

Arrays can be more performant when iterating through their elements since they do not require the overhead of a method call to retrieve each element.

Methods of Creating ArrayList

Creating an empty ArrayList and adding elements to it:
Creating an ArrayList with initial capacity and adding elements to it:
Creating an ArrayList from an existing collection:
Creating an ArrayList using the Collections.nCopies() method:
Creating a read-only ArrayList using the Collections.unmodifiableList() method:

syntax for creating an Array in Java

ArrayList arrayListName = new ArrayList<>();

ArrayList In Java

ArrayLists can resize dynamically to accommodate the number of elements they hold, which can be more flexible than arrays.

Inserting or removing elements from an ArrayList can be more efficient than doing so in an array because the elements do not need to be shifted in memory.

ArrayLists can be more convenient to use since they provide many built-in methods for manipulating their contents, such as adding, removing, and sorting elements.

A table comparing the Differences between Array and ArrayList In Java

Difference	Array	ArrayList
Size	Fixed	Dynamic
Memory	Contiguous	Non-Contiguous
Resizing	Cannot resize	Resizes automatically
Insertion/Deletion	Inefficient due to element shifting	Efficient due to dynamic resizing
Access	Direct access by index	Access through method calls
Type	Can hold primitives and objects	Can only hold objects
Convenience	No built-in methods for manipulation	Built-in methods for adding, removing, and sorting elements

Introduction to Java

How is Java a platform independent language

Methods In Java

Keywords and Variable

Strings In Java

Let’s look at the Difference between Array and ArrayList In Java to perform certain operations.

Example 1: How to create an Array?

Run

public class Main
{
  
public static void main (String[]args)
  {
    
int[] myArray = new int[5];
     
myArray[0] = 1;
     
myArray[1] = 2;
     
myArray[2] = 3;
     
myArray[3] = 4;
     
myArray[4] = 5;
     

System.out.print ("The elements of the array are: ");
     
for (int i = 0; i < myArray.length; i++)
      {
	
System.out.print (myArray[i] + " ");

} 
} 
}

Output

The elements of the array are: 1 2 3 4 5

Explanation:

We creates an array of size 5 and initializes its elements with the values 1 to 5. It then prints the elements of the array using a for loop.

Example 2 : Java Program to create two dimentional array

Run

import java.util.ArrayList;


public class Main
{

  public static void main (String[]args)
  {

    ArrayList < String > myArrayList = new ArrayList < String > ();

    myArrayList.add ("Prep");

    myArrayList.add ("Insta");

    myArrayList.add ("Prime");


    System.out.print ("The elements of the ArrayList are: ");

    for (int i = 0; i < myArrayList.size (); i++)
      {

	System.out.print (myArrayList.get (i) + " ");

      }
  }
}

Output

The elements of the ArrayList are: Prep Insta Prime

Explanation:

We creates an ArrayList of type String and adds three elements to it. It then prints the elements of the ArrayList using a for loop and the get() method.

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Questions and Answes

Question 1.Which is faster, arrays or ArrayLists?

Explanation

Arrays are generally faster than ArrayLists because they are a simpler data structure with less overhead.

Arrays are fixed in size, which means memory is allocated all at once, while ArrayLists may need to reallocate memory as they grow.

Accessing elements in an array is faster than accessing elements in an ArrayList because arrays store elements in contiguous memory locations, while an ArrayList may store elements in different parts of memory.

the performance difference between arrays and ArrayLists may not be significant for small collections, and the convenience of using an ArrayList may outweigh any performance considerations in certain situations.

Question 2. How are arrays and ArrayLists different?

Explanation

Size: Arrays have a fixed size, while ArrayLists can grow or shrink dynamically.

Memory allocation: Arrays allocate memory all at once when they are created, while ArrayLists may need to reallocate memory as they grow.

Contiguity of memory: Arrays store elements in contiguous memory locations, while an ArrayList may store elements in different parts of memory

Question 3. When should you use an array instead of an ArrayList?

Explanation

Arrays should be used instead of ArrayLists when you need to store a fixed number of elements and their size won’t change during the lifetime of the program. Arrays are simpler, more efficient, and offer direct index access to elements.

They can be used for simple collections, and may have better performance than ArrayLists for small collections that don’t need to be resized frequently.

Question 4.When should you use an ArrayList instead of an array?

Explanation

Using an ArrayList instead of an array when you need a dynamic collection that can grow or shrink in size during the lifetime of the program. ArrayLists offer convenient methods for adding, removing, and manipulating elements, making them suitable for complex collections.

They are also useful when the size of the collection is unknown, as they can automatically resize as needed.

However, ArrayLists are less efficient than arrays for small collections, and may require more memory due to their dynamic nature.

Question 5. How do you initialize the elements of an array

Explanation

To initialize the elements of an array, you can assign a value to each element when you create the array. You can also use a loop to set the value of each element after the array has been created. When initializing, make sure to specify the size of the array and the data type of the elements. Additionally, you can use the “Arrays.fill()” method to set all elements of an array to a specified value.

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Difference Between Array and ArrayList In Java

What is Array and Array List In Java?

Methods of Creating Array

Methods of Creating ArrayList

A table comparing the Differences between Array and ArrayList In Java

Let’s look at the Difference between Array and ArrayList In Java to perform certain operations.

Example 1: How to create an Array?

Output

Example 2 : Java Program to create two dimentional array

Output

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Get over 200+ course One Subscription

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