Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:
Once the early-adopter seats are all used, the price will go up and stay at $33/year.
Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.
Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.
To learn more about Java features on Azure Container Apps, visit the documentation page.
You can also ask questions and leave feedback on the Azure Container Apps GitHub page.
Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.
Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.
To learn more about Java features on Azure Container Apps, you can get started over on the documentation page.
And, you can also ask questions and leave feedback on the Azure Container Apps GitHub page.
Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.
Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.
With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.
Try a 14-Day Free Trial of Orkes Conductor today.
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:
All Access is finally out, with all of my Spring courses. Learn JUnit is out as well, and Learn Maven is coming fast. And, of course, quite a bit more affordable. Finally.
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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:
End-to-end testing is a very useful method to make sure that your application works as intended. This highlights issues in the overall functionality of the software, that the unit and integration test stages may miss.
Playwright is an easy-to-use, but powerful tool that automates end-to-end testing, and supports all modern browsers and platforms.
When coupled with LambdaTest (an AI-powered cloud-based test execution platform) it can be further scaled to run the Playwright scripts in parallel across 3000+ browser and device combinations:
Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:
Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:
1. Overview
The Java standard library has provided the String.toUpperCase() method, which allows us to convert all letters in a string to upper case.
In this tutorial, we’ll learn how to convert a given string’s first character only to upper case.
2. Introduction to the Problem
An example can explain this problem quickly. Let’s say we have an input string:
String INPUT = "hi there, Nice to Meet You!";Given this INPUT string, here’s our expected result:
String EXPECTED = "Hi there, Nice to Meet You!";As we can see, we only want the first character, ‘h‘, to be changed into ‘H‘. However, the remaining characters shouldn’t be modified.
Of course, if the input string is empty, the result should be an empty string too:
String EMPTY_INPUT = "";
String EMPTY_EXPECTED = "";In this tutorial, we’ll address several solutions to the problem. For simplicity, we’ll use unit test assertions to verify if our solution works as expected.
3. Using the substring() Method
The first idea to solve the problem is to split the input string into two substrings. For example, we can split the INPUT string to “h” and “i there, Nice ….“. In other words, the first substring contains only the first character, and the other substring holds the remaining characters of the strings.
Then, we can just apply the toUpperCase() method on the first substring and concatenate the second substring to solve the problem.
Java’s String class’s substring() method can help us to get the two substrings:
- INPUT.substring(0, 1) – substring 1 containing the first character
- INPUT.substring(1) – substring 2 holding the rest of the characters
So next, let’s write a test to see if the solution works:
String output = INPUT.substring(0, 1).toUpperCase() + INPUT.substring(1);
assertEquals(EXPECTED, output);If we run the test, it passes. However, if our input is an empty string, this approach will raise IndexOutOfBoundsException. This is because the end-index (1) is greater than the empty string’s length (0) when we call INPUT.substring(1):
assertThrows(IndexOutOfBoundsException.class, () -> EMPTY_INPUT.substring(1));Further, we should note that if the input string is null, this approach will throw NullPointerException.
Therefore, before using the substring approach, we need to check and ensure the input string is not null or empty.
4. Using the Matcher.replaceAll() Method
Another idea to solve the problem is to use regex (“^.“) to match the first character and convert the matched group to upper case.
It wasn’t an easy task before Java 9. This is because Matcher‘s replacement methods, such as replaceAll() and replaceFirst(), don’t support a Function object or a lambda expression replacer. However, this has changed in Java 9.
Since Java 9, Matcher‘s replacement methods support a Function object as the replacer. That is to say, we can use a function to process the matched character sequence and fulfill the replacement. Of course, to solve our problem, we just need to call the toUpperCase() method on the matched character:
String output = Pattern.compile("^.").matcher(INPUT).replaceFirst(m -> m.group().toUpperCase());
assertEquals(EXPECTED, output);The test passes if we give it a run.
If the regex matches nothing, the replacement won’t happen. Therefore, this solution works for empty input strings as well:
String emptyOutput = Pattern.compile("^.").matcher(EMPTY_INPUT).replaceFirst(m -> m.group().toUpperCase());
assertEquals(EMPTY_EXPECTED, emptyOutput);It’s worth mentioning that if the input string is null, this solution will throw NullPointerException too. So, we still need to do a null check before we use it.
5. Using StringUtils From Apache Commons Lang 3
Apache Commons Lang3 is a popular library. It ships with a lot of handy utility classes and extends the functionality of the standard Java library.
Its StringUtils class provides the capitalize() method, which solves our problem directly.
To use the library, let’s first add the Maven dependency:
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.12.0</version>
</dependency>Then, as usual, let’s create a test to see how it works:
String output = StringUtils.capitalize(INPUT);
assertEquals(EXPECTED, output);The test passes if we execute it. As we can see, we simply call StringUtils.capitalize(INPUT). Then the library does the job for us.
It’s worth mentioning that the StringUtils.capitalize() method is null-safe and works for empty input strings as well:
String emptyOutput = StringUtils.capitalize(EMPTY_INPUT);
assertEquals(EMPTY_EXPECTED, emptyOutput);
String nullOutput = StringUtils.capitalize(null);
assertNull(nullOutput);6. Conclusion
In this article, we’ve learned how to convert the first character of a given string to upper case.
The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.
