Array to ArrayList Conversion in Java

Last Updated : 02 Apr, 2025
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In Java, arrays are fixed-sized, whereas ArrayLists are part of the Java collection Framework and are dynamic in nature. Converting an array to an ArrayList is a very common task and there are several ways to achieve it.

Methods to Convert Array to an ArrayList

1. Using add() Method to Manually add the Array elements in the ArrayList

The easiest way to convert an array to an ArrayList is by manually adding elements one by one. This approach involves creating a new ArrayList and using the add() method to insert each element from the array.

Example:

Java 
// Java program to illustrate conversion 
// of an array to an ArrayList
import java.util.ArrayList;

public class Geeks {
    public static void convertUsingAdd(int[] arr) {
        ArrayList<Integer> al = new ArrayList<>();

        // Manually adding array elements to the ArrayList
        for (int i = 0; i < arr.length; i++) {
            al.add(arr[i]);
        }

        System.out.println(al);
    }

    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        convertUsingAdd(arr);
    }
}

Output
[1, 2, 3, 4, 5]

2. Using Arrays.asList() Method of java.utils.Arrays Class

The most efficient approach for converting Arrays to List is by using Arrays.asList() method. This method returns a fixed-size list backed by the specified array, which we can then pass to the constructor of an ArrayList.

Example:

Java 
// Java program to illustrate conversion
// of an array to an ArrayList
import java.util.ArrayList;
import java.util.Arrays;

public class Geeks {
    public static void convertUsingAsList(Integer[] arr) {
        ArrayList<Integer> al = new ArrayList<>(Arrays.asList(arr));
        System.out.println(al);
    }

    public static void main(String[] args) {
        Integer[] arr = {1, 2, 3, 4, 5};
        convertUsingAsList(arr);
    }
}

Output
[1, 2, 3, 4, 5]

3. Using Collections.addAll() Method of java.utils.Collections Class

Collections.addAll() is the efficient way to convert an array to an ArrayList. This method allows us to insert an array's element directly into a collection.

Example:

Java 
// Java program to illustrate conversion 
// of an array to an ArrayList
import java.util.ArrayList;
import java.util.Collections;

public class Geeks{
    public static void convertUsingAddAll(String[] arr) {
        ArrayList<String> al = new ArrayList<>();
        Collections.addAll(al, arr);
        System.out.println(al);
    }

    public static void main(String[] args) {
        String[] arr = {"A", "B", "C", "D"};
        convertUsingAddAll(arr);
    }
}

Output
[A, B, C, D]

4. Using Arrays.stream() and Collectors.toList()

From Java 8, with the help of streams we can convert an array to a ArrayList. The Arrays.stream() methods creates a stream from the array and the Collectors.toList() collects the stream elements into a list.

Example:

Java 
// Java program to illustrate conversion 
// of an array to an ArrayList
import java.util.ArrayList;
import java.util.Arrays;
import java.util.stream.Collectors;

public class Geeks {
    public static void convertUsingStream(String[] arr) {
        ArrayList<String> al = (ArrayList<String>) Arrays.stream(arr)
                .collect(Collectors.toList());
        System.out.println(al);
    }

    public static void main(String[] args) {
        String[] arr = {"Java", "Python", "C++"};
        convertUsingStream(arr);
    }
}

Output
[Java, Python, C++]

5. Using List.of(Elements) Method of java.utils.List Interface

From Java 9, we can use the List.of() method to create an immutable list from an array. This method is simple and clean but note that the resulting list is immutable, so you cannot modify it.

Syntax:

static {T} List{T} of(a)

  • Parameters: The method accepts a mandatory parameter ‘a’ which is the array to be converted and T signifies the list’s element type(this can be omitted).
  • Returns: The method returns a list containing the specified elements.
  • Exception(s): The method throws a NullPointerException if the array is null.

Example:

Java 
// Java program to illustrate conversion 
// of an array to an ArrayList
import java.util.ArrayList;
import java.util.List;

public class Geeks{
    public static void convertUsingListOf(String[] arr) {
        ArrayList<String> al = new ArrayList<>(List.of(arr));
        System.out.println(al);
    }

    public static void main(String[] args) {
        String[] arr = {"Geek1", "Geek2", "Geek3"};
        convertUsingListOf(arr);
    }
}

Output
[Geek1, Geek2, Geek3]

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Array to ArrayList Conversion in Java

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