Java Program to Convert the ArrayList to an array and vice versa

Example 1: Convert the Arraylist into Array

import java.util.ArrayList;

class Main {
  public static void main(String[] args) {
    ArrayList<String> languages= new ArrayList<>();

    // Add elements in the arraylist
    languages.add("Java");
    languages.add("Python");
    languages.add("JavaScript");
    System.out.println("ArrayList: " + languages);

    // Create a new array of String type
    String[] arr = new String[languages.size()];

    // Convert ArrayList into the string array
    languages.toArray(arr);
    System.out.print("Array: ");
    for(String item:arr) {
      System.out.print(item+", ");
    }
  }
}

Output

ArrayList: [Java, Python, JavaScript]
Array: Java, Python, JavaScript,

In the above example, we have created an arraylist named languages. Notice the line,

languages.toArray(arr);

Here, the toArray() method converts the arraylist languages into an array. And stores it in the string array arr.

Note: If we don't pass any argument to the toArray() method, the method returns an array of the Object type.

Example 2: Convert Array to ArrayList

import java.util.Arrays;
import java.util.ArrayList;

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

    // create an array
    String[] array = {"Java", "Python", "C"};
    System.out.println("Array: " + Arrays.toString(array));

    // convert array to arraylist
    ArrayList<String> languages= new ArrayList<>(Arrays.asList(array));

    System.out.println("ArrayList: " + languages);

  }
}

Output

Array: [Java, Python, C]
ArrayList: [Java, Python, C]

In the above example, we have created an array of String type. Notice the expression,

Arrays.asList(array)

Here, the asList() method of the Arrays class converts the specified array into the arraylist.