Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Distributed systems often come with complex challenges such as service-to-service communication, state management, asynchronous messaging, security, and more.
Dapr (Distributed Application Runtime) provides a set of APIs and building blocks to address these challenges, abstracting away infrastructure so we can focus on business logic.
In this tutorial, we'll focus on Dapr's pub/sub API for message brokering. Using its Spring Boot integration, we'll simplify the creation of a loosely coupled, portable, and easily testable pub/sub messaging system:
1. Overview
In this tutorial, we’ll learn how to convert a Queue object into a List in Java.
We’ll explain several popular ways of doing this along with their implementations, and we’ll end each section with a test case to test the respective implementation.
2. Ways to Convert Queue to List
In this section, we’ll cover different ways to convert the Queue to a List using standard Java classes and methods. We’re assuming a non-null queue for all examples.
2.1. Using the ArrayList Constructor
The ArrayList constructor provides the easiest and most common way to convert a Queue to an ArrayList.
The idea is to pass the Queue as a parameter to the ArrayList constructor:
List<String> list = new ArrayList<>(queue);The constructor new ArrayList<>(queue) efficiently inserts all of the queue elements into the new ArrayList.
2.2. Using the addAll() Method
The addAll() method is another great option to consider if we want to convert a Queue to a List.
As the name implies, this method allows adding all elements in the specified collection to the List.
Now, let’s see the logic:
List<String> list = new ArrayList<>();
list.addAll(queue);We create a new List named list and populate it with the elements of the queue using the addAll() method. The method then returns the resultant list.
2.3. Using the LinkedList Constructor
The LinkedList constructor provides the most common and easiest way to convert a Queue to a LinkedList.
Similar to the above example using the ArrayList constructor, we simply pass the Queue as a parameter to the LinkedList constructor:
LinkedList<String> list = new LinkedList<>(queue);The constructor new LinkedList<>(queue) efficiently converts the queue elements into the new LinkedList.
2.4. Using Stream API
Java 8 comes with a lot of new features that help in enhancing our code. Among these features, we find the Stream API.
Let’s illustrate how to use the stream API to convert a Queue to a List:
List<String> list = queue.stream().collect(Collectors.toList());We convert the queue to a List using the collect(Collectors.toList()) operation, which collects the elements of the stream into a new list and returns it. This approach leverages a concise and functional programming style with streams to perform the conversion.
2.5. Using Guava
Guava is a popular open-source library developed by Google that provides a wide range of utility classes and methods to simplify common programming tasks in Java.
Let’s use Guava to convert Queue to List:
List<String> list = Lists.newArrayList(queue);Guava’s utility method Lists.newArrayList(queue) simplifies the process of creating a new list from the elements of a queue.
3. Conclusion
In this article, we saw various ways to convert Queue to List in Java. Whether we prefer the simplicity of LinkedList, the versatility of ArrayList, the elegance of Java 8 streams, or the power of Guava, understanding these techniques empowers us to handle data seamlessly in our Java projects. We can experiment with these approaches to find the one best suited to our requirements and coding style.
