How to convert an ArrayList to array in Java

Today, I will share a very basic Java program that converts an ArrayList to an array. For most Java developers this is a routine task, but many newcomers to Java have asked me this question of how to convert an array to ArrayList. Here is the example code.

import java.util.*;
public class ArrayToArrayList{
   public static void main(String args[]){
     //Create an ArrayList of Strings.
    ArrayList<String> list = new ArrayList<String>();
    //Populate the ArrayList.
    list.add("A1");
    list.add("A2");
    list.add("A3");
    list.add("A4");
    list.add("A5");
    list.add("A6");
    /*Initialize a String array. 
    Set array's capacity equal to ArrayList size*/
    String[] array = new String[list.size()];
    //Now get the array from ArrayList. There is no magic here. 
   //We are calling toArray method of the ArrayList class.     	
   array = list.toArray(array);
   }
}

How to convert a Java Array to a List

In some instances, you may need to convert an array to a list. This is also a simple task. Using the array variable defined in the example above, we can call asList method of the Arrays class to get a List variable from the array.

List<String> list2 = Arrays.asList(array);

A more modern way to do the conversion (Java 11+)

The example above pre-sizes the target array (new String[list.size()]) before calling toArray. Since Java 11 you can skip that and let toArray allocate the correctly-sized array itself with a method reference — it’s shorter and, according to the JDK’s own Collection.toArray docs, actually faster in most cases because the JVM can generate the array directly via reflection instead of the caller pre-allocating one:

String[] array = list.toArray(String[]::new);

This still works exactly the same way on JDK 21.

Enjoy!