Introduction:

In Java, the ArrayList and Array are two fundamental data structures with distinct characteristics. Sometimes, there arises a need to convert an ArrayList to an Array or vice versa, depending on the requirements of a program. In this blog, we will explore various methods to convert an ArrayList to an Array in Java, providing detailed explanations and examples.

Method 1: Using the toArray() Method

The toArray() method is a convenient approach provided by the ArrayList class to convert the ArrayList to an Array. It returns an Array containing all the elements of the ArrayList in the same order.

import java.util.ArrayList;

public class ArrayListToArray {
    public static void main(String[] args) {
        ArrayList<String> arrayList = new ArrayList<>();
        arrayList.add("Hello");
        arrayList.add("World");
        
        String[] array = new String[arrayList.size()];
        array = arrayList.toArray(array);
        
        for (String element : array) {
            System.out.println(element);
        }
    }
}

Output:

Hello
World

In this method, we first create an ArrayList and add some elements to it. Then, we create an Array of the same type and size as the ArrayList. The toArray() method is invoked on the ArrayList, passing the Array as an argument. This method returns the Array containing all the elements of the ArrayList. Finally, we iterate over the Array and print its elements.

Method 2: Manual Conversion

If you prefer a manual approach, you can convert an ArrayList to an Array by iterating through the ArrayList and copying its elements into the Array.

import java.util.ArrayList;

public class ArrayListToArray {
    public static void main(String[] args) {
        ArrayList<Integer> arrayList = new ArrayList<>();
        arrayList.add(1);
        arrayList.add(2);
        arrayList.add(3);
        
        Integer[] array = new Integer[arrayList.size()];
        
        for (int i = 0; i < arrayList.size(); i++) {
            array[i] = arrayList.get(i);
        }
        
        for (int element : array) {
            System.out.println(element);
        }
    }
}

Output:

1
2
3

In this approach, we create an ArrayList and populate it with some elements. Next, we create an Array of the same type as the ArrayList. We iterate through the ArrayList using a loop and copy each element to the corresponding position in the Array. Finally, we iterate over the Array and print its elements.

Conclusion:

In this blog, we explored different methods to convert an ArrayList to an Array in Java. We started with the toArray() method, which is provided by the ArrayList class itself. Then, we discussed a manual approach involving iteration and element copying. Understanding these techniques will help you choose the most appropriate approach based on your project's needs.