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 article, we’ll look at a core aspect of the Java language – executing a statement or a group of statements repeatedly using a for loop.
2. Simple for Loop
A for loop is a control structure that allows us to repeat certain operations by incrementing and evaluating a loop counter.
Before the first iteration, the loop counter gets initialized, then the condition evaluation is performed followed by the step definition (usually a simple incrementation).
The syntax of the for loop is:
for (initialization; Boolean-expression; step)
statement;Let’s see it in a simple example:
for (int i = 0; i < 5; i++) {
System.out.println("Simple for loop: i = " + i);
}The initialization, Boolean-expression, and step used in for statements are optional. Here’s an example of an infinite for loop:
for ( ; ; ) {
// Infinite for loop
}2.1. Labeled for Loops
We can also have labeled for loops. It’s useful if we’ve got nested for loops so that we can break/continue from aspecific for loop:
aa: for (int i = 1; i <= 3; i++) {
if (i == 1)
continue;
bb: for (int j = 1; j <= 3; j++) {
if (i == 2 && j == 2) {
break aa;
}
System.out.println(i + " " + j);
}
}3. Enhanced for Loop
Since Java 5, we have a second kind of for loop called the enhanced for which makes it easier to iterate over all elements in an array or a collection.
The syntax of the enhanced for loop is:
for(Type item : items)
statement;Since this loop is simplified in comparison to the standard for loop, we need to declare only two things when initializing a loop:
- The handle for an element we’re currently iterating over
- The source array/collection we’re iterating
Therefore, we can say that: For each element in items, assign the element to the item variable and run the body of the loop.
Let’s have a look at the simple example:
int[] intArr = { 0,1,2,3,4 };
for (int num : intArr) {
System.out.println("Enhanced for-each loop: i = " + num);
}We can use it to iterate over various Java data structures:
Given a List<String> list object – we can iterate it:
for (String item : list) {
System.out.println(item);
}We can similarly iterate over a Set<String> set:
for (String item : set) {
System.out.println(item);
}And, given a Map<String,Integer> map we can iterate over it as well:
for (Entry<String, Integer> entry : map.entrySet()) {
System.out.println(
"Key: " + entry.getKey() +
" - " +
"Value: " + entry.getValue());
}3.1. Iterable.forEach()
Since Java 8, we can leverage for-each loops in a slightly different way. We now have a dedicated forEach() method in the Iterable interface that accepts a lambda expression representing an action we want to perform.
Internally, it simply delegates the job to the standard loop:
default void forEach(Consumer<? super T> action) {
Objects.requireNonNull(action);
for (T t : this) {
action.accept(t);
}
}Let’s have a look at the example:
List<String> names = new ArrayList<>();
names.add("Larry");
names.add("Steve");
names.add("James");
names.add("Conan");
names.add("Ellen");
names.forEach(name -> System.out.println(name));4. Conclusion
In this quick tutorial, we explored Java’s for loop.
