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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.

Try a 14-Day Free Trial of Orkes Conductor today.

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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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.

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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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eBook – HTTP Client – NPI EA (cat=Http Client-Side)
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eBook – Persistence – NPI EA (cat=Persistence)
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eBook – RwS – NPI EA (cat=Spring MVC)
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Building a REST API with Spring?

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Course – LS – NPI EA (cat=Jackson)
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Get started with Spring and Spring Boot, through the Learn Spring course:

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Course – RWSB – NPI EA (cat=REST)
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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

In this quick tutorial, we’ll look at two basic building blocks of the Java programming language – classes and objects. They’re basic concepts of Object Oriented Programming (OOP), which we use to model real-life entities.

In OOP, classes are blueprints or templates for objects. We use them to describe types of entities.

On the other hand, objects are living entities, created from classes. They contain certain states within their fields and present certain behaviors with their methods.

2. Classes

Simply put, a class represent a definition or a type of object. In Java, classes can contain fields, constructors, and methods.

Let’s see an example using a simple Java class representing a Car:

class Car {

    // fields
    String type;
    String model;
    String color;
    int speed;

    // constructor
    Car(String type, String model, String color) {
        this.type = type;
        this.model = model;
        this.color = color;
    }
    
    // methods
    int increaseSpeed(int increment) {
        this.speed = this.speed + increment;
        return this.speed;
    }
    
    // ...
}

This Java class represents a car in general. We can create any type of car from this class. We use fields to hold the state and a constructor to create objects from this class.

Every Java class has an empty constructor by default. We use it if we don’t provide a specific implementation as we did above. Here’s how the default constructor would look for our Car class:

Car(){}

This constructor simply initializes all fields of the object with their default values. Strings are initialized to null and integers to zero.

Now, our class has a specific constructor because we want our objects to have their fields defined when we create them:

Car(String type, String model) {
    // ...
}

To sum up, we wrote a class that defines a car. Its properties are described by fields, which contain the state of objects of the class, and its behavior is described using methods.

3. Objects

While classes are translated during compile time, objects are created from classes at runtime.

Objects of a class are called instances, and we create and initialize them with constructors:

Car focus = new Car("Ford", "Focus", "red");
Car auris = new Car("Toyota", "Auris", "blue");
Car golf = new Car("Volkswagen", "Golf", "green");

Now, we’ve created different Car objects, all from a single class. This is the point of it all, to define the blueprint in one place, and then, to reuse it many times in many places.

So far, we have three Car objects, and they’re all parked since their speed is zero. We can change this by invoking our increaseSpeed method:

focus.increaseSpeed(10);
auris.increaseSpeed(20);
golf.increaseSpeed(30);

Now, we’ve changed the state of our cars – they’re all moving at different speeds.

Furthermore, we can and should define access control to our class, its constructors, fields, and methods. We can do so by using access modifiers, as we’ll see in the next section.

4. Access Modifiers

In the previous examples, we omitted access modifiers to simplify the code. By doing so, we actually used a default package-private modifier. That modifier allows access to the class from any other class in the same package.

Usually, we’d use a public modifier for constructors to allow access from all other objects:

public Car(String type, String model, String color) {
    // ...
}

Every field and method in our class should’ve also defined access control by a specific modifier. Classes usually have public modifiers, but we tend to keep our fields private.

Fields hold the state of our object, therefore we want to control access to that state. We can keep some of them private, and others public. We achieve this with specific methods called getters and setters.

Let’s have a look at our class with fully-specified access control:

public class Car {
    private String type;
    // ...

    public Car(String type, String model, String color) {
       // ...
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public int getSpeed() {
        return speed;
    }

    // ...
}

Our class is marked public, which means we can use it in any package. Also, the constructor is public, which means we can create an object from this class inside any other object.

Our fields are marked private, which means they’re not accessible from our object directly, but we provide access to them through getters and setters.

The type and model fields do not have getters and setters, because they hold internal data of our objects. We can define them only through the constructor during initialization.

Furthermore, the color can be accessed and changed, whereas speed can only be accessed, but not changed. We enforced speed adjustments through specialized public methods increaseSpeed() and decreaseSpeed().

In other words, we use access control to encapsulate the state of the object.

5. Conclusion

In this article, we went through two basic elements of the Java language, classes, and objects, and showed how and why they are used. We also introduced the basics of access control and demonstrated its usage.

To learn other concepts of Java language, we suggest reading about inheritance, the super keyword, and abstract classes as a next step.

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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Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:

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