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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.

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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.

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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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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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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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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.

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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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Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:

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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.

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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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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.

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1. Overview

Finding an element in a list is a very common task we come across as developers.

In this quick tutorial, we’ll cover different ways we can do this with Java.

Further reading:

Checking If a List Is Sorted in Java

Learn several algorithms for checking whether a list is sorted in Java.

Java List Initialization in One Line

In this quick tutorial, we'll investigate how can we initialize a List using one-liners.

2. Setup

First let’s start by defining a Customer POJO:

public class Customer {

    private int id;
    private String name;
    
    // getters/setters, custom hashcode/equals
}

Then an ArrayList of customers:

List<Customer> customers = new ArrayList<>();
customers.add(new Customer(1, "Jack"));
customers.add(new Customer(2, "James"));
customers.add(new Customer(3, "Kelly"));

Note that we’ve overridden hashCode and equals in our Customer class.

Based on our current implementation of equals, two Customer objects with the same id will be considered equal.

We’ll use this list of customers along the way.

3. Using Java API

Java itself provides several ways of finding an item in a list:

  • The contains method
  • The indexOf method
  • An ad-hoc for loop
  • The Stream API

3.1. contains()

List exposes a method called contains:

boolean contains(Object element)

As the name suggests, this method returns true if the list contains the specified element, and returns false otherwise. 

So when we need to check if a specific item exists in our list, we can:

Customer james = new Customer(2, "James");
if (customers.contains(james)) {
    // ...
}

3.2. indexOf()

indexOf is another useful method for finding elements:

int indexOf(Object element)

This method returns the index of the first occurrence of the specified element in the given list, or -1 if the list doesn’t contain the element.

So logically, if this method returns anything other than -1, we know that the list contains the element:

if(customers.indexOf(james) != -1) {
    // ...
}

The main advantage of using this method is that it can tell us the position of the specified element in the given list.

3.3. Basic Looping

Now what if we want to do a field-based search for an element? For example, say we’re announcing a lottery and we need to declare a Customer with a specific name as the winner.

For such field-based searches, we can turn to iteration.

A traditional way of iterating through a list is to use one of Java’s looping constructs. In each iteration, we compare the current item in the list with the element we’re looking for to see if it’s a match:

public Customer findUsingEnhancedForLoop(
  String name, List<Customer> customers) {

    for (Customer customer : customers) {
        if (customer.getName().equals(name)) {
            return customer;
        }
    }
    return null;
}

Here the name refers to the name we are searching for in the given list of customers. This method returns the first Customer object in the list with a matching name, or null if no such Customer exists.

3.4. Looping With an Iterator

Iterator is another way that we can traverse a list of items.

We can simply take our previous example and tweak it a bit:

public Customer findUsingIterator(
  String name, List<Customer> customers) {
    Iterator<Customer> iterator = customers.iterator();
    while (iterator.hasNext()) {
        Customer customer = iterator.next();
        if (customer.getName().equals(name)) {
            return customer;
        }
    }
    return null;
}

Consequently, the behavior is the same as before.

3.5. Java 8 Stream API

As of Java 8, we can also use the Stream API to find an element in a List.

To find an element matching specific criteria in a given list, we:

  • invoke stream() on the list
  • call the filter() method with a proper Predicate
  • call the findAny() construct, which returns the first element that matches the filter predicate wrapped in an Optional if such an element exists
Customer james = customers.stream()
  .filter(customer -> "James".equals(customer.getName()))
  .findAny()
  .orElse(null);

For convenience, we default to null in case an Optional is empty, but this might not always be the best choice for every scenario.

4. Third-Party Libraries

Now, while the Stream API is more than sufficient, what should we do if we’re stuck on an earlier version of Java?

Fortunately, there are many third-party libraries like Google Guava and Apache Commons which we can use.

4.1. Google Guava

Google Guava provides functionality that is similar to what we can do with streams:

Customer james = Iterables.tryFind(customers,
  new Predicate<Customer>() {
      public boolean apply(Customer customer) {
          return "James".equals(customer.getName());
      }
  }).orNull();

Just like with Stream API, we can optionally choose to return a default value instead of null:

Customer james = Iterables.tryFind(customers,
  new Predicate<Customer>() {
      public boolean apply(Customer customer) {
          return "James".equals(customer.getName());
      }
  }).or(customers.get(0));

The above code will pick the first element in the list if no match is found.

Also, don’t forget that Guava throws a NullPointerException if either the list or the predicate is null.

4.2. Apache Commons

We can find an element in almost the exact same way using Apache Commons:

Customer james = IterableUtils.find(customers,
  new Predicate<Customer>() {
      public boolean evaluate(Customer customer) {
          return "James".equals(customer.getName());
      }
  });

There are a couple of important differences though:

  1. Apache Commons just returns null if we pass a null list.
  2. It doesn’t provide default value functionality like Guava’s tryFind.

5. Conclusion

In this article, we learned different ways of finding an element in a List, starting with quick existence checks and finishing with field-based searches.

We also looked at the third-party libraries Google Guava and Apache Commons as alternatives to the Java 8 Streams API.

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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