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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

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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.

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 – Guide Spring Cloud – NPI EA (cat=Spring Cloud)
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Let's get started with a Microservice Architecture with 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.

Get started with mocking and improve your application tests using our Mockito guide:

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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:

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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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Get the most out of the Apache HTTP Client

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eBook – Maven – NPI EA (cat = Maven)
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Get Started with Apache Maven:

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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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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:

>> The New “REST With Spring Boot”

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:

>> Learn Spring Security

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.

Get started with Spring Data JPA through the guided reference course:

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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:

>> Automated End-to-End Testing With Playwright

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 (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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1. Introduction

In this quick tutorial, we’ll cover the basics of packages in Java. We’ll see how to create packages and access the types we place inside them.

We’ll also discuss naming conventions and how that relates to the underlying directory structure.

Finally, we’ll compile and run our packaged Java classes.

2. Overview of Java Packages

In Java, we use packages to group related classes, interfaces, and sub-packages.

The main benefits of doing this are:

  • Making related types easier to find – packages usually contain types that are logically related
  • Avoiding naming conflicts – a package will help us to uniquely identify a class; for example, we could have a com.baeldung.Application, as well as com.example.Application classes
  • Controlling access – we can control visibility and access to types by combining packages and access modifiers

Next, let’s see how we can create and use Java packages.

3. Creating a Package

To create a package, we have to use the package statement by adding it as the very first line of code in a file.

Let’s place a type in a package named com.baeldung.packages:

package com.baeldung.packages;

It’s highly recommended to place each new type in a package. If we define types and don’t place them in a package, they will go in the default or unnamed package. Using default packages comes with a few disadvantages:

  • We lose the benefits of having a package structure and we can’t have sub-packages
  • We can’t import the types in the default package from other packages
  • The protected and package-private access scopes would be meaningless

As the Java language specification states, unnamed packages are provided by the Java SE Platform principally for convenience when developing small or temporary applications or when just beginning development.

Therefore, we should avoid using unnamed or default packages in real-world applications.

3.1. Naming Conventions

In order to avoid packages with the same name, we follow some naming conventions:

  • we define our package names in all lower case
  • package names are period-delimited
  • names are also determined by the company or organization that creates them

To determine the package name based on an organization, we’ll typically start by reversing the company URL. After that, the naming convention is defined by the company and may include division names and project names.

For example, to make a package out of www.baeldung.com, let’s reverse it:

com.baeldung

We can then further define sub-packages of this, like com.baeldung.packages or com.baeldung.packages.domain.

3.2. Directory Structure

Packages in Java correspond with a directory structure.

Each package and subpackage has its own directory. So, for the package com.baeldung.packages, we should have a directory structure of com -> baeldung -> packages.

Most IDE’s will help with creating this directory structure based on our package names, so we don’t have to create these by hand.

4. Using Package Members

Let’s start by defining a class TodoItem in a subpackage named domain:

package com.baeldung.packages.domain;

public class TodoItem {
    private Long id;
    private String description;
    
    // standard getters and setters
}

4.1. Imports

In order to use our TodoItem class from a class in another package, we need to import it. Once it’s imported, we can access it by name.

We can import a single type from a package or use an asterisk to import all of the types in a package.

Let’s import the entire domain subpackage:

import com.baeldung.packages.domain.*;

Now, let’s import only the TodoItem class:

import com.baeldung.packages.domain.TodoItem;

The JDK and other Java libraries also come with their own packages. We can import pre-existing classes that we want to use in our project in the same manner.

For example, let’s import the Java core List interface and ArrayList class:

import java.util.ArrayList;import java.util.List;

We can then use these types in our application by simply using their name:

public class TodoList {
    private List<TodoItem> todoItems;

    public void addTodoItem(TodoItem todoItem) {
        if (todoItems == null) {
            todoItems = new ArrayList<TodoItem>();
        }
        todoItems.add(todoItem);
    }
}

Here, we’ve used our new classes along with Java core classes, to create a List of ToDoItems.

4.2. Fully Qualified Name

Sometimes, we may be using two classes with the same name from different packages. For example, we might be using both java.sql.Date and java.util.Date. When we run into naming conflicts, we need to use a fully qualified class name for at least one of the classes.

Let’s use TodoItem with a fully qualified name:

public class TodoList {
    private List<com.baeldung.packages.domain.TodoItem> todoItems;

    public void addTodoItem(com.baeldung.packages.domain.TodoItem todoItem) {
        if (todoItems == null) {
            todoItems = new ArrayList<com.baeldung.packages.domain.TodoItem>();
        }todoItems.add(todoItem);
    }

    // standard getters and setters
}

5. Compiling with javac

When it’s time to compile our packaged classes, we need to remember our directory structure. Starting in the source folder, we need to tell javac where to find our files.

We need to compile our TodoItem class first because our TodoList class depends on it.

Let’s start by opening a command line or terminal and navigating to our source directory.

Now, let’s compile our com.baeldung.packages.domain.TodoItem class:

> javac com/baeldung/packages/domain/TodoItem.java

If our class compiles cleanly, we’ll see no error messages and a file TodoItem.class should appear in our com/baeldung/packages/domain directory.

For types that reference types in other packages, we should use the -classpath flag to tell the javac command where to find the other compiled classes.

Now that our TodoItem class is compiled, we can compile our TodoList and TodoApp classes:

>javac -classpath . com/baeldung/packages/*.java

Again, we should see no error messages and we should find two class files in our com/baeldung/packages directory.

Let’s run our application using the fully qualified name of our TodoApp class:

>java com.baeldung.packages.TodoApp

Our output should look like this:

packages

6. Conclusion

In this short article, we learned what a package is and why we should use them.

We discussed naming conventions and how packages relate to the directory structure. We also saw how to create and use packages.

Finally, we went over how to compile and run an application with packages using the javac and java commands.

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:

>> Join Pro and download the eBook

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:

>> CHECK OUT THE COURSE

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

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eBook Jackson – NPI EA – 3 (cat = Jackson)