ArrayList toArray() method in Java with Examples

The toArray() method of ArrayList is used to return an array containing all the elements in ArrayList in the correct order.

Declaring toArray() method

public Object[] toArray()
           
           or
           
public <T> T[] toArray(T[] a)

Parameters: This method either accepts no parameters or it takes an array T[] as a parameter which is the array into which the elements of the list are to be stored if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.

Return Value: The function returns an array containing all the elements in this list.

Exception: The first overload of this method throws no exceptions. However, the second overload throws the following exceptions:

• ArrayStoreException: if the runtime type of the specified array is not a supertype of the runtime type of every element in this list.
• NullPointerException if the specified array is null

Examples of Java ArrayList.toArray() method

Example 1 :Converting an ArrayList to an Array using toArray() Method in Java

The following Java program demonstrates how to convert an ArrayList to an array using the toArray() method. This example showcases the basic usage of the ArrayList and how its elements can be retrieved and stored in the array.

// Java Program to illustrate the
// ArrayList toArray() method in Java

import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // create object of ArrayList
        ArrayList<Integer> ArrLis
            = new ArrayList<Integer>();

        // Add elements
        ArrLis.add(32);
        ArrLis.add(67);
        ArrLis.add(98);
        ArrLis.add(100);

        // print ArrayList
        System.out.println("ArrayList: " + ArrLis);

        // Get the array of the elements
        // of the ArrayList
        // using toArray() method
        Object[] arr = ArrLis.toArray();

        System.out.println("Elements of ArrayList"
                           + " as Array: "
                           + Arrays.toString(arr));
    }
}

ArrayList: [32, 67, 98, 100]
Elements of ArrayList as Array: [32, 67, 98, 100]

Explanation of the Program:

• This Java program demonstrates the use of ArrayList's toArray() method to convert its elements into a regular array.
• First, integers are added to the ArrayList.
• Then, the toArray() method is called to obtain an array representation of the ArrayList's elements, which is printed using Arrays.toString(arr).

Example 2 : Converting an ArrayList to a Typed Array using toArray(T[]) Method in Java

This Java program demonstrates how to convert an ArrayList of integers into an array of the integers using the toArray(T[]) method. This method is particularly useful when we want to specify the type of the array ensuring the type safety and avoiding the need for the type casting.

// Java Program to illustrate the
// ArrayList toArray(T[]) method in Java

import java.util.*;

// Driver Class
public class GFG {
    // main function
    public static void main(String[] args)
    {
        // create object of ArrayList
        ArrayList<Integer> ArrLis
            = new ArrayList<Integer>();

        // Add elements
        ArrLis.add(32);
        ArrLis.add(67);
        ArrLis.add(98);
        ArrLis.add(100);

        // print ArrayList
        System.out.println(" ArrayList: " + ArrLis);

        // Get the array of the elements
        // of the ArrayList
        // using toArray(T[]) method
        Integer arr[] = new Integer[ArrLis.size()];
        arr = ArrLis.toArray(arr);

        System.out.println(" Elements of ArrayList "
                           + "as Array: "
                           + Arrays.toString(arr));
    }
}

 ArrayList: [32, 67, 98, 100]
 Elements of ArrayList as Array: [32, 67, 98, 100]

Explanation of the Program:

• This Java program showcases the ArrayList method toArray(T[]), which converts an ArrayList to an array of specified type T.
• First, integers are added to ArrLis.
• Then, an Integer array of the same size is initialized and passed to toArray(arr) to obtain the array representation of ArrLis, printed using Arrays.toString(arr).