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. Introduction
Splitting Strings is a very frequent operation; this quick tutorial is focused on some of the API we can use to do this simply in Java.
2. String.split()
Let’s start with the core library – the String class itself offers a split() method – which is very convenient and sufficient for most scenarios. It simply splits the given String based on the delimiter, returning an array of Strings.
Let us look at some examples. We’ll start with splitting by a comma:
String[] splitted = "peter,james,thomas".split(",");Let’s split by a whitespace:
String[] splitted = "car jeep scooter".split(" ");Let’s also split by a dot:
String[] splitted = "192.168.1.178".split("\\.")Let’s now split by multiple characters – a comma, space, and hyphen through regex:
String[] splitted = "b a, e, l.d u, n g".split("\\s+|,\\s*|\\.\\s*"));3. StringUtils.split()
Apache’s common lang package provides a StringUtils class – which contains a null-safe split() method, that splits using whitespace as the default delimiter:
String[] splitted = StringUtils.split("car jeep scooter");Furthermore, it ignores extra spaces:
String[] splitted = StringUtils.split("car jeep scooter");4. Splitter.split()
Finally, there’s a nice Splitter fluent API in Guava as well:
List<String> resultList = Splitter.on(',')
.trimResults()
.omitEmptyStrings()
.splitToList("car,jeep,, scooter");
5. Split and Trim
Sometimes a given String contains some leading, trailing, or extra spaces around the delimiter. Let’s see how we can handle splitting the input and trimming the results in one go.
Let’s say we have this as an input:
String input = " car , jeep, scooter ";To remove extra spaces before and/or after the delimiter, we can perform split and trim using regex:
String[] splitted = input.trim().split("\\s*,\\s*");Here, trim() method removes leading and trailing spaces in the input string, and the regex itself handles the extra spaces around delimiter.
We can achieve the same result by using Java 8 Stream features:
String[] splitted = Arrays.stream(input.split(","))
.map(String::trim)
.toArray(String[]::new);6. Splitting String Into Two Halves
We can split a string into two parts by getting its midpoint and using substring() to get the separated parts.
Here’s an example that splits a string in half:
String hello = "Baeldung";
int mid = hello.length() / 2;
String[] parts = { hello.substring(0, mid), hello.substring(mid) };Here, we calculate the midpoint of the string value. Next, we use the substring() method to get the first and second parts of the string value by specifying the ranges.
7. Conclusion
String.split() is generally enough. However, for more complex cases we can utilize Apache’s commons-lang based StringUtils class, or the clean and flexible Guava APIs.
