How to Convert Array to List in Java 8

Introduction

In Java, it's common to work with arrays and lists. While arrays have a fixed size, lists are more flexible. Java 8 provides an easy and efficient way to convert an array to a list using Streams and utility methods. In this guide, we will explore different ways to convert an array to a list in Java 8.

Problem Statement

You have an array, and you want to convert it into a list. Write a program that:

• Takes an array as input.
• Converts the array to a list.
• Displays the list.

Example:

• Input: {"Java", "Python", "C++"}
• Output: ["Java", "Python", "C++"]

Solution Steps

1. Define the Input Array: Define an array that you want to convert to a list.
2. Use Utility Methods: Use Arrays.asList() or Streams to convert the array to a list.
3. Display the Result: Print the converted list.

Method 1: Using Arrays.asList()

Java Program

import java.util.Arrays;
import java.util.List;

public class ArrayToListExample1 {
    public static void main(String[] args) {
        // Step 1: Define the input array
        String[] array = {"Java", "Python", "C++"};

        // Step 2: Convert the array to a list using Arrays.asList()
        List<String> list = Arrays.asList(array);

        // Step 3: Display the result
        System.out.println("List: " + list);
    }
}

Output

List: [Java, Python, C++]

Explanation

• Arrays.asList(array) converts the array into a fixed-size list. This method is simple but has a limitation: the returned list is fixed in size, meaning you cannot add or remove elements.

Method 2: Using Java 8 Streams

Java Program

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class ArrayToListExample2 {
    public static void main(String[] args) {
        // Step 1: Define the input array
        String[] array = {"Java", "Python", "C++"};

        // Step 2: Convert the array to a list using Java 8 Streams
        List<String> list = Arrays.stream(array)
            .collect(Collectors.toList());

        // Step 3: Display the result
        System.out.println("List: " + list);
    }
}

Output

List: [Java, Python, C++]

Explanation

• Arrays.stream(array) creates a stream from the array.
• Collectors.toList() collects the elements from the stream into a new list.
• This method allows you to create a modifiable list, meaning you can add or remove elements from the list.

Method 3: Using Collections.addAll()

Java Program

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class ArrayToListExample3 {
    public static void main(String[] args) {
        // Step 1: Define the input array
        String[] array = {"Java", "Python", "C++"};

        // Step 2: Convert the array to a list using Collections.addAll()
        List<String> list = new ArrayList<>();
        Collections.addAll(list, array);

        // Step 3: Display the result
        System.out.println("List: " + list);
    }
}

Output

List: [Java, Python, C++]

Explanation

• Collections.addAll() adds all elements of the array into a new ArrayList.
• This method creates a modifiable list, allowing you to add or remove elements later.

Output Example

Example 1:

For the input {"Java", "Python", "C++"}, the output for all methods will be:

List: [Java, Python, C++]

Example 2:

For the input {"Apple", "Banana", "Orange"}, the output will be:

List: [Apple, Banana, Orange]

Conclusion

There are several ways to convert an array to a list in Java 8. Using Arrays.asList() is quick and simple but results in a fixed-size list. On the other hand, using Java 8 Streams or Collections.addAll() allows for the creation of modifiable lists. Depending on your requirements (fixed or modifiable list), you can choose the method that best suits your needs.