Array vs. ArrayList in Java

In Java programming, there are two ways to create an array.

  • Array: Is a simple fixed-size data structure which requires a size at the time of creation.

  • ArrayList: Is a dynamic sized data structure which doesn’t require a specific size at the time of initialization.

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Array

An Array can contain both primitive data types or objects of a class depending on the definition of the array. But it has a fixed size.

Example

// Importing the required libraries
import java.util.Arrays; 
class Array 
{ 
    public static void main(String args[]) 
    { 
        /* ...........Array............. */
        // Fixed size. 
        // Cannot add more than 3 elements.
        int[] arr = new int[3]; 
        arr[0] = 5; 
        arr[1] = 6; 
        arr[2] = 10; 
         
        // Printing
        System.out.println(Arrays.toString(arr)); 
    } 
}

ArrayList

An ArrayList can’t be created for primitive data types. It only contains an object. It has the ability to grow and shrink dynamically.

  • Remember that in Java, every primitive data type has a wrapper class. | Primitive | Wrapper class | | — | — | | int | Integer | | short | Short | | byte | Byte | | char | Character | | float | Float |

Example

// Importing required libraries
import java.util.ArrayList; 
class Array_List 
{ 
    public static void main(String args[]) 
    { 
        /*............ArrayList..............*/
        // Variable size.
        // Can add more elements.  
        ArrayList<Integer> arr = new ArrayList<Integer>(); 
        arr.add(5); 
        arr.add(9); 
        arr.add(11); 
        // Printing
        System.out.println(arr); 
    } 
}

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