Java – Page 2 – Natan Code

Timezones in Java: How to Schedule Classes Correctly Across Time Zones?

Imagine you’re developing a platform like Cambly, where students and teachers are spread across the globe. A student in Brazil wants to schedule a class at 10:00 AM local time with a teacher living in Australia. How can you ensure that both are connected at the right time, even though they’re in different time zones?…

How to avoid race condition in shared resources in Java?

Sharing resources between threads can be a challenging task, as it requires ensuring that operations are atomic. What is a resource? A resource can be variables, data structures, files, messages, etc. In Java, we have two important memory areas: the Stack and the Heap. Why use shared resources between threads? There are many reasons, but…

How to use Kafka with Quarkus?

Apache Kafka is one of the most popular solutions for large-scale distributed event streaming. Its ability to handle high volumes of messages makes it ideal for event-driven architectures. In this post, you’ll learn how to use Kafka with Quarkus, a modern framework for cloud-native Java applications. Best of all: Quarkus’ Kafka support also works with…

What are Checked vs Unchecked Exceptions in Java?

In Java, exceptions are part of the Throwable hierarchy and are used to signal abnormal situations during the execution of a program. Understanding how exceptions are structured helps in designing more robust and readable code. At the top of the hierarchy is the Throwable class, which has two direct subclasses: Checked Exceptions Checked exceptions are…

How to paginate using Spring Data JPA?

Spring Data JPA enables pagination through the JpaRepository interface, which extends PagingAndSortingRepository — an interface that provides pagination support. Let’s go over more details with a practical example. If you need to understand how Spring Data JPA works, there are more articles on the blog explaining that: Hands on You’ll need some of the following…

What’s the difference between Concurrency and Parallelism?

Concurrency and Parallelism are important concepts for bringing more efficiency to software, but they do not mean the same thing. A software application can handle multiple tasks, and the way these tasks are processed differs in each concept. Concurrency Imagine the scenario where we have a software that needs to process multiple tasks, such as…

How to create a custom repository in Spring Data JPA?

Spring Data JPA is great for abstracting away boilerplate code when accessing the database. It allows us to create query methods by simply defining method signatures. But sometimes, we need more complex or dynamic queries — and that’s where custom repositories come into play. In this post, I’ll show how to create a custom repository…

What is Spring Data JPA?

Spring Data JPA is a module of Spring Data that simplifies the implementation of repositories. It provides an automatic way to create repository implementations based on Java interfaces, eliminating the need to manually write the repository implementation. To make this work, you need to create an interface using the @Repository annotation and extend JpaRepository. The…

How to avoid NullPointerException in Java using Optional?

Optional was introduced in Java 8 as a way to handle potentially null values more safely and expressively. It helps to avoid NullPointerException and makes the code more readable. Hands on Creating an Optional Optional can be created in several ways: Printing the results will show the following output. Checking for Value Presence Optional provides…

What is algorithm complexity?

Algorithm complexity is a fundamental concept in computer science, used to measure the efficiency of an algorithm in terms of execution time and memory usage. By analyzing complexity, we can predict how an algorithm behaves as the input size increases, allowing us to choose more appropriate solutions for different problems. How do we measure it?…