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.
In distributed systems, managing multi-step processes (e.g., validating a driver, calculating fares, notifying users) can be difficult. We need to manage state, scattered retry logic, and maintain context when services fail.
Dapr Workflows solves this via Durable Execution which includes automatic state persistence, replaying workflows after failures and built-in resilience through retries, timeouts and error handling.
In this tutorial, we'll see how to orchestrate a multi-step flow for a ride-hailing application by integrating Dapr Workflows and Spring Boot:
1. Overview
In this tutorial, we’ll demonstrate the conversion from Java’s LocalDate to Epoch and vice versa.
2. Epoch vs. LocalDate
To do the conversion, it is important to understand the concept behind Epoch and LocalDate. The ‘Epoch‘ in Java refers to the time instant of 1970-01-01T00:00:00Z. Time instants after the Epoch will have positive values. Similarly, any time instants before the Epoch will have negative values.
All instances of Epoch, LocalDate, and LocalDateTime are timezone-dependent, hence, when converting from one to another, we have to know the timezone. In Java, a timezone can be represented through the ZoneId class. ZoneId can be the system’s timezone obtained through the method ZoneId.systemDefault(). Alternatively, ZoneId can be computed by passing a String for a known timezone such as Europe/Amsterdam.
3. Epoch to Date/Time
We can compute LocalDate or LocalDateTime given the number of milliseconds since the epoch. Alternatively, the count can be in seconds or seconds with nanoseconds adjustment. The Java data type for this count is Long. Finally, we also need to know the timezone. Let’s see how to do the conversion:
long milliSecondsSinceEpoch = 2131242L;
ZoneId zoneId = ZoneId.of("Europe/Amsterdam");
LocalDate date = Instant.ofEpochMilli(milliSecondsSinceEpoch).atZone(zoneId).toLocalDate();In the above code snippet, we have the number of milliseconds since the Epoch in the timezone of Amsterdam, so we can use the ofEpochMilli() method of class Instant to get the LocalDate value. Otherwise, if we want to have the time instead of the date, then we’d write:
LocalDateTime time = Instant.ofEpochMilli(milliSecondsSinceEpoch).atZone(zoneId).toLocalDateTime();In the above code snippet, we used the same approach but used the toLocalDateTime method.
4. Date/Time to Epoch
If we have a date available as LocalDate in a given timezone, then we can get the Epoch in seconds. Let’s see how:
ZoneId zoneId = ZoneId.of("Europe/Tallinn");
LocalDate date = LocalDate.now();
long EpochMilliSecondsAtDate = date.atStartOfDay(zoneId).toInstant().toEpochMilli();In the above example, we get the Epoch seconds for today’s date and the timezone in which the system is currently in. Note that we can only get the Epoch count for the start of the day. This is because LocalDate does not have any time value information. Alternatively, if we do have the time component, we can get the exact Epoch count at a given instant:
LocalDateTime localDateTime = LocalDateTime.parse("2019-11-15T13:15:30");
long epochMilliSecondsAtTime = localDateTime.atZone(zoneId).toInstant().toEpochMilli();5. Conclusion
In this article, we explored how to convert from Epoch to LocalDate and LocalDateTime. We also demonstrated how to convert LocalDate or LocalDateTime to Epoch.
