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 quick tutorial, we’ll see how to set the time zone of a date using Java 7, Java 8 and the Joda-Time library.
2. Using Java 8
Java 8 introduced a new Date-Time API for working with dates and times which was largely based off of the Joda-Time library.
The Instant class from Java Date Time API models a single instantaneous point on the timeline in UTC. This represents the count of nanoseconds since the epoch of the first moment of 1970 UTC.
First, we’ll obtain the current Instant from the system clock and ZoneId for a time zone name:
Instant nowUtc = Instant.now();
ZoneId asiaSingapore = ZoneId.of("Asia/Singapore");Finally, the ZoneId and Instant can be utilized to create a date-time object with time-zone details. The ZonedDateTime class represents a date-time with a time-zone in the ISO-8601 calendar system:
ZonedDateTime nowAsiaSingapore = ZonedDateTime.ofInstant(nowUtc, asiaSingapore);We’ve used Java 8’s ZonedDateTime to represent a date-time with a time zone.
3. Using Java 7
In Java 7, setting the time-zone is a bit tricky. The Date class (which represents a specific instant in time) doesn’t contain any time zone information.
First, let’s get the current UTC date and a TimeZone object:
Date nowUtc = new Date();
TimeZone asiaSingapore = TimeZone.getTimeZone(timeZone);In Java 7, we need to use the Calendar class to represent a date with a time zone.
Finally, we can create a nowUtc Calendar with the asiaSingapore TimeZone and set the time:
Calendar nowAsiaSingapore = Calendar.getInstance(asiaSingapore);
nowAsiaSingapore.setTime(nowUtc);It’s recommended to avoid the Java 7 date time API in favor of Java 8 date time API or the Joda-Time library.
4. Using SimpleDateFormat
When working with legacy systems that rely on Java 7, we might need to handle dates with timezone information in string format. In such cases, we can use java.util.Date along with SimpleDateFormat to include the timezone details. Let’s look at an example:
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");
sdf.setTimeZone(TimeZone.getTimeZone("Asia/Kolkata"));
Date date = new Date(1725437542000L);
Assert.assertEquals("2024-09-04 13:42:22 +0530", sdf.format(date));In this example, we create a SimpleDateFormat to define the desired date format, including the timezone. We then set the timezone for the formatter. Finally, we use the formatter to convert the java.util.Date instance into a string with the date, time, and timezone information.
If we need to manipulate date and time information, it’s better to use Joda-Time for a Java 7 codebase, as it provides a more comprehensive and flexible API for working with dates and times compared to java.util.Date and SimpleDateFormat.
5. Using Joda-Time
If Java 8 isn’t an option, we can still get the same kind of result from Joda-Time, a de-facto standard for date-time operations in the pre-Java 8 world.
First, we need to add the Joda-Time dependency to pom.xml:
<dependency>
<groupId>joda-time</groupId>
<artifactId>joda-time</artifactId>
<version>2.10</version>
</dependency>To represent an exact point on the timeline we can use Instant from org.joda.time package. Internally, the class holds one piece of data, the instant as milliseconds from the Java epoch of 1970-01-01T00:00:00Z:
Instant nowUtc = Instant.now();We’ll use DateTimeZone to represent a time-zone (for the specified time zone id):
DateTimeZone asiaSingapore = DateTimeZone.forID("Asia/Singapore");Now the nowUtc time will be converted to a DateTime object using the time zone information:
DateTime nowAsiaSingapore = nowUtc.toDateTime(asiaSingapore);This is how Joda-time API can be used to combine date and time zone information.
6. Conclusion
In this article, we found out how to set the time zone in Java using Java 7, 8 and Joda-Time API. To learn more about Java 8’s date-time support check out our Java 8 date-time intro.
