Java Collection toArray() Method

The toArray() method of Java Collection returns an array containing elements that are inside the calling collection. This article will discuss the toArray() method, its syntaxes, how it works, and some code examples.

Syntax of toArray() Method

Object[] toArray();

Return Type: The return type of the above syntax is Object[] (Array).

Examples of Java toArray() Method

The example given below returns an array of type Object containing elements as of list1. We use this syntax when we don't want a particular return type.

Below is the implementation of the above method:

// Java Program to Java toArray() Method
import java.io.*;
import java.util.ArrayList;
import java.util.List;

// Driver Class
class GFG {
    // main function
    public static void main(String[] args)
    {
        List<Integer> list1 = new ArrayList<Integer>();

        list1.add(1);
        list1.add(2);
        list1.add(3);
        list1.add(4);

        Object[] array = list1.toArray();

        System.out.print("The Array contains : ");

        for (int i = 0; i < array.length; i++) {
            System.out.print(array[i] + " ");
        }
    }
}

The Array contains : 1 2 3 4 

Overloaded toArray() Method

This overloaded method of toArray() returns an array containing all elements inside the collection where the type of the returned array is what we specify inside the argument of the toArray() method.

Syntax of Method

<T> T[]  toArray(T[] arr);

Parameter: T denotes the type of element stored in the collection
Return Type: The return type is what we specify inside the argument(i.e. T).

Example of Overloaded toArray() Method

In the example below, we have made some changes we need to understand before going further.

 String[] array=list1.toArray(new String[0]);

This line is different from the above example. Here in this line, we have passed a string array as an argument to the function. Due to this, it returns us an array of string type (i.e. name array in this example ) having the same size and containing all the elements as of calling collection list1.

Note: The major advantage of using the overloaded Overloaded toArray() method is it provides compile-time type safety as it returns an array of specific type only(e.g. Integer,String etc.) but the first syntax returns an array of Object type.

Example of Overloaded toArray() Method

Below is the implementation of the above method:

import java.io.*;
import java.util.ArrayList;
import java.util.List;

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

        List<String> list1 = new ArrayList<String>();

        list1.add("Pen");
        list1.add("Paper");
        list1.add("Rubber");
        list1.add("Pencil");

        String[] array = list1.toArray(new String[0]);

        System.out.println("The Array contains : ");

        for (int i = 0; i < array.length; i++) {
            System.out.print(array[i] + " ");
        }
    }
}

The Array contains : 
Pen Paper Rubber Pencil