ArrayList Vs Array in Java

Last Updated: 15 January, 2023

ArrayList is a class of the Collection Framework, and it implements the List interface.

Whereas, An array is an object in Java that contains the same data type of values. Its length is fixed once created and cannot be changed.

There are many differences between the ArrayList and Array that are given below.

👉 ArrayList

ArrayList in Java is a concrete class of the List interface that was introduced in the JDK 1.2 version and is available in the java.util package. An ArrayList is used to store a dynamically sized collection of elements. An ArrayList grows in size automatically. Elements can be added, modified, and removed from an ArrayList whenever there is a need.

Java ArrayList Class Declaration

public class ArrayList<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable

Here, E defines the type of elements that the List will contain.

Java ArrayList important features:

ArrayList extends the AbstractList class and implements the List, RandomAccess, Cloneable, and Serializable interfaces.
ArrayList is an ordered collection, so it maintains the insertion order of the elements.
ArrayList allows duplicate and null elements.
By default, an ArrayList is not synchronized. If multiple threads try to modify an ArrayList at the same time, then the final outcome will be non-deterministic.
ArrayList does not accept primitive types like int, char, etc. We need to use boxed types like Integer, Character, Boolean, etc.
ArrayList allows random access because the array works on an index basis.
Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. The default capacity is 10.
ArrayList performance is a bit slower than LinkedList because a lot of shifting operations are needed if we insert or delete elements in the middle of the ArrayList.

👉 Array

An array is an object in Java that contains the same data type of values. Its length is fixed once created and cannot be changed.

An Array allocates contiguous memory location for each element in Java.

Each item in an array is called an element, and each element is accessed by its unique numerical index value which starts from 0 which means the first element of the array will be stored at the 0th index position, 2nd element will be stored on the 1st index position and so on. With the help of the index number, we can directly access any random value from the array.

Java Array Syntax:

  // First way to create array
  data-type[] array-name;
  
  // Second way to create array
  data-type array-name[];
  
  // Third way to create array
  data-type []array-name;

data-type: data-type may be primitive (int, char, float etc.) or not-primitive (Objects) data.
array-name: Its a name of the array.
[ ]: Its known as subscript operator.

👉 ArrayList and Array have the following differences:

ArrayList	Array
The size of an arrayList is dynamic and can be increased or decreased as needed.	Array size is fixed. Once declared, its size can’t be changed.
ArrayList can only be one dimension.	An array can be single or multidimensional.
ArrayList can only hold reference types (objects), not primitives.	An array can hold both primitives and reference types (objects) in Java.
ArrayList supports generics.	Array does not support generics.
When compared to an array, an ArrayList performs worse and consumes more memory.	Array provides better performance and uses less memory.
ArralyList provides various ways for iteration, like loops, Iterator and ListIterator class.	We can iterate through an array using loops only.
ArrayList elements are not stored at contiguous memory locations.	Array elements are stored at contiguous memory locations.
We can add elements to the ArrayList using the add () method.	Using the assignment operator, we can add elements to the array.

👉 Example of ArrayList and Array in Java

Example 1: A sample Java program of ArrayList

  import java.util.ArrayList;
  class ArrayListExample {
    public static void main(String[] args){
      // Creating ArrayList
      ArrayList<String> countries = new ArrayList<>();
      // Adding elements in ArrayList
      countries.add("India");
      countries.add("Canada");
      countries.add("US");
      countries.add("England");
      // Printing ArrayList elements
      System.out.println("ArrayList Elements: " + countries);
    }
  }

Output

ArrayList Elements: [India, Canada, US, England]

Example 2: A sample Java program of Array

  public class ArrayExample {
    public static void main(String[] args) {
  
      // Array Declaration, Instantiation and Initialization
      char[] values = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J'};
      
      // Printing Array Element with Index value using for loop
      for (int i = 0; i < 10; i++) {
        System.out.println("Index: " + i + ", Element: " + values[i]);
      }
    }
  }

Output

Index: 0, Element: A
Index: 1, Element: B
Index: 2, Element: C
Index: 3, Element: D
Index: 4, Element: E
Index: 5, Element: F
Index: 6, Element: G
Index: 7, Element: H
Index: 8, Element: I
Index: 9, Element: J

As given above example, here we are declaring 10 characters size of Array which means Array length is 10 and storing values like A, B, C, D, E, F, G, H, I, J. Since at the time of array declaration, the character 'A' is declared first and then 'B' character and so on, therefore 'A' will be store at the 0 index position and 'B' will be store at index 1 and so on as we can see in the below image.

That's all guys, hope this Java article is helpful for you.

Happy Learning... 😀

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