Java ArrayList toArray() Method

Java ArrayList

The toArray() method converts an ArrayList object into an array.

The syntax for the toArray() method is:

arraylist.toArray(T[] arr)

Note: arraylist is an object of the ArrayList class.

Parameter Description:

T[] arr (optional parameter) - The array to store the elements.

Note: Here, T refers to the type of the array.

Return Value

If the parameter T[] arr is passed to the method, it returns an array of type T.

If no parameter is passed, it returns an array of type Object.

Example

Using an array parameter of specified type:

Example

import java.util.ArrayList;
import java.util.Comparator;
class Main {
    public static void main(String[] args){

        // Create a dynamic array
        ArrayList<String> sites = new ArrayList<>();

        sites.add("tutorialpro");
        sites.add("Google");
        sites.add("Wiki");
        sites.add("Taobao");
        System.out.println("Website List: " + sites);

        // Create a new array of type String
        // The array length is the same as the ArrayList length
        String[] arr = new String[sites.size()];

        // Convert ArrayList object to array
        sites.toArray(arr);

        // Print all elements of the array
        System.out.print("Array: ");
        for(String item:arr) {
            System.out.print(item+", ");
        }
    }
}

Executing the above program outputs:

Website List: [tutorialpro, Google, Wiki, Taobao]
Array: tutorialpro, Google, Wiki, Taobao,

In the above example, we used the sort() method on the array named sites.

Notice this line:

sites.toArray(arr);

Here, we passed a String type array as a parameter, and all elements are stored in the string array.

Note: The length of the array parameter passed should be equal to or greater than the arraylist. Here, we used the ArrayList size() method to create an array of the same size as the arraylist.

Using the toArray() method without parameters:

Example

import java.util.ArrayList;
import java.util.Comparator;
class Main {
    public static void main(String[] args){

        // Create a dynamic array
        ArrayList<String> sites = new ArrayList<>();

        sites.add("tutorialpro");
        sites.add("Google");
        sites.add("Wiki");
        sites.add("Taobao");
        System.out.println("Website List: " + sites);

        // Convert ArrayList object to array
        // This method does not take parameters
        Object[] obj = sites.toArray();

        // Print all elements of the array
        System.out.print("Array: ");
        for(Object item : obj) {
            System.out.print(item+", ");
        }
    }
}

Executing the above program outputs:

Website List: [tutorialpro, Google, Wiki, Taobao]
Array: tutorialpro, Google, Wiki, Taobao,

In the example above, we used toArray() to convert an ArrayList to an array.

Note: It is recommended to use the toArray() method with parameters.

Java ArrayList

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