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Once the early-adopter seats are all used, the price will go up and stay at $33/year.

Partner – Microsoft – NPI EA (cat = Baeldung)
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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.

Partner – Microsoft – NPI EA (cat= Spring Boot)
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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.

Partner – Orkes – NPI EA (cat=Spring)
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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.

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Partner – Orkes – NPI EA (tag=Microservices)
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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.

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eBook – Guide Spring Cloud – NPI EA (cat=Spring Cloud)
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eBook – Mockito – NPI EA (tag = Mockito)
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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.

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eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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eBook – Reactive – NPI EA (cat=Reactive)
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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:

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eBook – Java Streams – NPI EA (cat=Java Streams)
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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:

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eBook – Jackson – NPI EA (cat=Jackson)
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Do JSON right with Jackson

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Course – LS – NPI EA (cat=Jackson)
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Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:

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Course – LSS – NPI EA (cat=Spring Security)
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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:

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Course – All Access – NPI EA (cat= Spring)
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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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Course – LSD – NPI EA (tag=Spring Data JPA)
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Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.

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Partner – LambdaTest – NPI EA (cat=Testing)
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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:

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Course – Spring Sale 2025 – NPI EA (cat= Baeldung)
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1. Overview

While inheritance enables us to reuse existing code, sometimes we do need to set limitations on extensibility for various reasons; the final keyword allows us to do exactly that.

In this tutorial, we’ll take a look at what the final keyword means for classes, methods, and variables.

2. Final Classes

Classes marked as final can’t be extended. If we look at the code of Java core libraries, we’ll find many final classes there. One example is the String class.

Consider the situation if we can extend the String class, override any of its methods, and substitute all the String instances with the instances of our specific String subclass.

The result of the operations over String objects will then become unpredictable. And given that the String class is used everywhere, it’s unacceptable. That’s why the String class is marked as final.

Any attempt to inherit from a final class will cause a compiler error. To demonstrate this, let’s create the final class Cat:

public final class Cat {

    private int weight;

    // standard getter and setter
}

And let’s try to extend it:

public class BlackCat extends Cat {
}

We’ll see the compiler error:

The type BlackCat cannot subclass the final class Cat

Note that the final keyword in a class declaration doesn’t mean that the objects of this class are immutable. We can change the fields of Cat object freely:

Cat cat = new Cat();
cat.setWeight(1);

assertEquals(1, cat.getWeight());

We just can’t extend it.

If we follow the rules of good design strictly, we should create and document a class carefully or declare it final for safety reasons. However, we should use caution when creating final classes.

Notice that making a class final means that no other programmer can improve it. Imagine that we’re using a class and don’t have the source code for it, and there’s a problem with one method.

If the class is final, we can’t extend it to override the method and fix the problem. In other words, we lose extensibility, one of the benefits of object-oriented programming.

3. Final Methods

Methods marked as final cannot be overridden. When we design a class and feel that a method shouldn’t be overridden, we can make this method final. We can also find many final methods in Java core libraries.

Sometimes we don’t need to prohibit a class extension entirely, but only prevent overriding of some methods. A good example of this is the Thread class. It’s legal to extend it and thus create a custom thread class. But its isAlive() methods is final.

This method checks if a thread is alive. It’s impossible to override the isAlive() method correctly for many reasons. One of them is that this method is native. Native code is implemented in another programming language and is often specific to the operating system and hardware it’s running on.

Let’s create a Dog class and make its sound() method final:

public class Dog {
    public final void sound() {
        // ...
    }
}

Now let’s extend the Dog class and try to override its sound() method:

public class BlackDog extends Dog {
    public void sound() {
    }
}

We’ll see the compiler error:

- overrides
com.baeldung.finalkeyword.Dog.sound
- Cannot override the final method from Dog
sound() method is final and can’t be overridden

If some methods of our class are called by other methods, we should consider making the called methods final. Otherwise, overriding them can affect the work of callers and cause surprising results.

If our constructor calls other methods, we should generally declare these methods final for the above reason.

What’s the difference between making all methods of the class final and marking the class itself final? In the first case, we can extend the class and add new methods to it.

In the second case, we can’t do this.

4. Final Variables

Variables marked as final can’t be reassigned. Once a final variable is initialized, it can’t be altered.

4.1. Final Primitive Variables

Let’s declare a primitive final variable i, then assign 1 to it.

And let’s try to assign a value of 2 to it:

public void whenFinalVariableAssign_thenOnlyOnce() {
    final int i = 1;
    //...
    i=2;
}

The compiler says:

The final local variable i may already have been assigned

4.2. Final Reference Variables

If we have a final reference variable, we can’t reassign it either. But this doesn’t mean that the object it refers to is immutable. We can change the properties of this object freely.

To demonstrate this, let’s declare the final reference variable cat and initialize it:

final Cat cat = new Cat();

If we try to reassign it we’ll see a compiler error:

The final local variable cat cannot be assigned. It must be blank and not using a compound assignment

But we can change the properties of Cat instance:

cat.setWeight(5);

assertEquals(5, cat.getWeight());

4.3. Final Fields

Final fields can be either constants or write-once fields. To distinguish them, we should ask a question — would we include this field if we were to serialize the object? If no, then it’s not part of the object, but a constant.

Note that according to naming conventions, class constants should be uppercase, with components separated by underscore (“_”) characters:

static final int MAX_WIDTH = 999;

Note that any final field must be initialized before the constructor completes.

For static final fields, this means that we can initialize them:

  • upon declaration as shown in the above example
  • in the static initializer block

For instance final fields, this means that we can initialize them:

  • upon declaration
  • in the instance initializer block
  • in the constructor

Otherwise, the compiler will give us an error.

4.4. Final Parameters

The final keyword is also legal to put before method parameters. A final parameter can’t be changed inside a method:

public void methodWithFinalArguments(final int x) {
    x=1;
}

The above assignment causes the compiler error:

The final local variable x cannot be assigned. It must be blank and not using a compound assignment

5. Conclusion

In this article, we learned what the final keyword means for classes, methods, and variables. Although we may not use the final keyword often in our internal code, it may be a good design solution.

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.
Baeldung Pro – NPI EA (cat = Baeldung)
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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

>> Explore a clean Baeldung

Once the early-adopter seats are all used, the price will go up and stay at $33/year.

Partner – Microsoft – NPI EA (cat = Spring Boot)
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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.

Partner – Orkes – NPI EA (cat = Spring)
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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.

Partner – Orkes – NPI EA (tag = Microservices)
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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.

eBook – HTTP Client – NPI EA (cat=HTTP Client-Side)
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The Apache HTTP Client is a very robust library, suitable for both simple and advanced use cases when testing HTTP endpoints. Check out our guide covering basic request and response handling, as well as security, cookies, timeouts, and more:

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eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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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:

>> Download the eBook

eBook – Java Streams – NPI EA (cat=Java Streams)
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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:

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eBook – Persistence – NPI EA (cat=Persistence)
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Working on getting your persistence layer right with Spring?

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Course – LS – NPI EA (cat=REST)

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Get started with Spring Boot and with core Spring, through the Learn Spring course:

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Course – Spring Sale 2025 – NPI EA (cat= Baeldung)
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Course – Spring Sale 2025 – NPI (All)
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eBook Jackson – NPI EA – 3 (cat = Jackson)