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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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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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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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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:

>> 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.

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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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eBook – Java Streams – NPI (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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1. Overview

In this tutorial, we’ll look at different methods to get a List from a Stream. We’ll also discuss the differences among them, and when to use each method.

2. Collecting Stream Elements Into a List

Getting a List from a Stream is the most used terminal operation of the Stream pipeline. Before Java 16, we used to invoke the Stream.collect() method and pass it to a Collector as an argument to gather the elements into. The Collector itself was created by calling the Collectors.toList() method.

However, there have been change requests for a method to get a List directly from a Stream instance. With the Java 16 release, we can now invoke toList(), a new method directly on the Stream, to get the List. Libraries, like StreamEx, also provide a convenient way to get a List directly from a Stream.

We can accumulate Stream elements into a List by using:

We’ll work with these methods in the chronological order of their release.

3. Analyzing the Lists

We’ll first create the lists from the methods described in the previous section. Then we’ll analyze their properties.

We’ll use the following Stream of country codes for all the examples:

Stream.of(Locale.getISOCountries());

3.1. Creating Lists

Now we’ll create a List from the given Stream of country codes using the different methods.

First, we’ll create a List using Collectors:toList():

List<String> result = Stream.of(Locale.getISOCountries()).collect(Collectors.toList());

Then we’ll collect it using Collectors.toUnmodifiableList():

List<String> result = Stream.of(Locale.getISOCountries()).collect(Collectors.toUnmodifiableList());

Here, in these methods, we accumulate the Stream into a List through the Collector interface. This results in extra allocation and copying, as we don’t work directly with the Stream.

Next, we’ll repeat the collection with Stream.toList():

List<String> result = Stream.of(Locale.getISOCountries()).toList();

Here, we get the List directly from the Stream, thus preventing extra allocation and copying.

Consequently, using toList() directly on the Stream is more concise, neat, convenient, and optimal when compared to the other two invocations.

3.2. Examining the Accumulated Lists

Let’s begin by examining the type of List we created.

Collectors.toList() collects the Stream elements into an ArrayList:

java.util.ArrayList

Collectors.toUnmodifiableList() collects the Stream elements into an unmodifiable List:

java.util.ImmutableCollections.ListN

Stream.toList() collects the elements into an unmodifiable List:

java.util.ImmutableCollections.ListN

Though the current implementation of the Collectors.toList() creates a mutable List, the method’s specification itself makes no guarantee on the type, mutability, serializability, or thread-safety of the List.

On the other hand, both Collectors.toUnmodifiableList() and Stream.toList() produce unmodifiable lists.

This implies that we can do operations like add and sort on the elements of Collectors.toList(), but not on the elements of Collectors.toUnmodifiableList() and Stream.toList()

3.3. Allowing Null Elements in the Lists

Although Stream.toList() produces an unmodifiable List, it’s still not the same as Collectors.toUnmodifiableList(). This is because Stream.toList() allows the null elements, and Collectors.toUnmodifiableList() doesn’t allow the null elements. However, Collectors.toList() allows the null elements.

Collectors.toList() doesn’t throw an Exception when a Stream containing null elements is collected:

Assertions.assertDoesNotThrow(() -> {
    Stream.of(null,null).collect(Collectors.toList());
});

Collectors.toUnmodifiableList() throws a NulPointerException when we collect a Stream containing null elements:

Assertions.assertThrows(NullPointerException.class, () -> {
    Stream.of(null,null).collect(Collectors.toUnmodifiableList());
});

Stream.toList() doesn’t throw a NulPointerException when we try to collect a Stream containing null elements:

Assertions.assertDoesNotThrow(() -> {
    Stream.of(null,null).toList();
});

Therefore, this is something to watch out for when migrating our code from Java 8 to Java 10 or Java 16. We can’t blindly use Stream.toList() in place of Collectors.toList() or Collectors.toUnmodifiableList().

3.4. Summary of Analysis

The following table summarizes the differences and similarities of the lists from our analysis:

stream list summary

4. When to Use Different toList() Methods

The main objective of adding Stream.toList() is to reduce the verbosity of the Collector API.

As shown previously, using the Collectors methods for getting Lists is very verbose. On the other hand, using the Stream.toList() method makes code neat and concise.

Nevertheless, as seen in earlier sections, Stream.toList() can’t be used as a shortcut to Collectors.toList() or Collectors.toUnmodifiableList().

Secondly, the Stream.toList() uses less memory because its implementation is independent of the Collector interface. It accumulates the Stream elements directly into the List. So if we know the size of the stream in advance, it’ll be optimal to use Stream.toList().

We also know that the Stream API provides the implementation only for the toList() method. It doesn’t contain similar methods for getting a map or a set. So if we want a uniform approach to get any converters, like list, map, or set, we’ll continue to use the Collector API. This will also maintain consistency and avoid confusion.

Finally, if we’re using versions lower than Java 16, we have to continue to use Collectors methods.

The following table summarizes the optimum use of the given methods:

comparison

5. Conclusion

In this article, we analyzed the three most popular ways of getting a List from a Stream. Then we looked at the main differences and similarities. We also discussed how and when to use these methods.

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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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 – Java Streams – NPI (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 Jackson – NPI EA – 3 (cat = Jackson)
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