Exploring the Real World Applications of Java 17 with Use Cases and Comprehensive Code Examples

Java has long been a key player in the programming world, recognized for its flexibility and strength. With the introduction of Java 17, developers gain access to a range of exciting features that enhance its capabilities.

Java 17, released in September 2021, is a Long-Term Support (LTS) version, making it one of the most stable and reliable releases for enterprise-grade applications. Many companies migrated from Java 8 and Java 11 to Java 17 because of its performance improvements, new language features, and security updates.

In this blog, we will explore the key features of Java 17, their real-world use cases, and code examples to help you understand why upgrading to Java 17 can make a huge difference in your projects.

Key Features of Java 17

Java 17 is a Long-Term Support (LTS) release, ensuring ongoing support and updates for many years. Some of its standout features include:

• Sealed Classes: Allow developers to define which classes can extend or implement them, promoting better design.

• Pattern Matching for `instanceof`: Streamlines type checks and casts, simplifying your code.

  
  

• New macOS Rendering Pipeline: Improves performance for Java applications running on macOS systems.

  
  

• JEP 411: Deprioritizes the Security Manager for future removal, showcasing how the language adapts to changing security needs.

  
  

These features not only elevate the language but also enhance the overall developer experience, making Java 17 an attractive option for new projects.

1. Sealed Classes and Interfaces

Sealed classes allow developers to define restricted class hierarchies. Only specific classes or interfaces are allowed to extend or implement them.

Real-World Use Case

Imagine building a payment system where you want to restrict the types of payments: CreditCard, UPI, and NetBanking. No other payment types should be allowed.

Example

public sealed class Payment permits CreditCard, UPI, NetBanking {}

final class CreditCard extends Payment {}
final class UPI extends Payment {}
final class NetBanking extends Payment {}

Now, if another developer tries to create a new payment type (like CryptoPayment), the compiler will prevent it.

This ensures domain-driven design enforcement and better security.

2. Pattern Matching for switch (Preview)

Java 17 introduced pattern matching with switch, making it easier to handle complex type checks and casting.

Use Case

In a customer support application, different types of users (Admin, Moderator, Guest) may require different access levels.

Example

static String getAccessLevel(Object user) {
    return switch (user) {
        case Admin a    -> "Full Access";
        case Moderator m -> "Limited Access";
        case Guest g     -> "Read-Only Access";
        default          -> "No Access";
    };
}

This eliminates boilerplate code with instanceof checks and makes the switch statement more concise and readable.

3. Records (Standard Feature)

Records, introduced in Java 14 as a preview, became standard in Java 16 and are fully supported in Java 17. They allow easy creation of immutable data carriers without boilerplate code.

Use Case

For a banking system, you often need simple data transfer objects like Transaction.

Example

public record Transaction(String id, double amount, String status) {}

Using record, you automatically get:

• Constructor

• Getters

• toString(), equals(), and hashCode()

Makes DTOs lightweight and clean for microservices and REST APIs.

4. Enhanced Pseudo-Random Number Generators

Java 17 introduced a new set of interfaces for Random Number Generators (RNGs) with better algorithms.

Use Case

In e-commerce flash sales, you might need randomized queue assignments for fairness.

Example

import java.util.random.RandomGenerator;
import java.util.random.RandomGeneratorFactory;

public class FlashSale {
    public static void main(String[] args) {
        RandomGenerator rng = RandomGeneratorFactory.of("L64X128MixRandom").create();
        System.out.println("User Queue Number: " + rng.nextInt(1000));
    }
}

Provides more reliable randomness for gaming, simulations, and cryptographic use cases.

5. JDK Internals Encapsulation (Strong Encapsulation)

Java 17 strongly encapsulates JDK internals, except for a few critical APIs (like sun.misc.Unsafe).

Use Case

In legacy projects, developers often used internal APIs. With Java 17, such usage is restricted to prevent accidental misuse and improve security.

This ensures safer enterprise applications and encourages developers to use official APIs.

6. Foreign Function & Memory API (Incubator)

Java 17 introduced a powerful API for interacting with native libraries without JNI.

Use Case

Suppose you are building a high-performance AI/ML application and need to integrate with a C++ library for matrix operations.

This API allows efficient interoperability with native code, reducing overhead and improving performance.

7. Deprecations and Removals

• RMI Activation system removed (rarely used).

• Applet API deprecated (modern browsers don’t support applets).

• Security manager deprecated for removal in future releases.

Encourages modernization and prevents reliance on outdated technology.

8. Performance and Garbage Collection Improvements

• ZGC and Shenandoah became production-ready, providing low-latency garbage collection.

• Ideal for financial systems, gaming servers, and real-time applications.

Example: A stock trading platform can now process thousands of transactions per second with reduced GC pause times.

Conclusion

Java 17 brings seamless improvements in performance, syntax, security, and maintainability. With features like sealed classes, pattern matching for switch, enhanced RNGs, and strong encapsulation, enterprises can build faster, safer, and more scalable applications.

If you are still using Java 8 or Java 11, upgrading to Java 17 ensures long-term support and helps future-proof your systems.

Project Use Case-1: Building a RESTful API

One of Java's primary applications is in developing RESTful APIs. With the growth of microservices architecture, Java 17 equips developers with the necessary tools to create efficient APIs that can scale effectively.

Example: Creating a Simple RESTful API for Book Management

Let’s build a straightforward RESTful API designed to manage a collection of books. This example will utilize Java 17 features, particularly sealed classes and pattern matching.

Step 1: Setting Up the Project

Start by establishing a Maven project. Here’s a basic `pom.xml` configuration:

<project xmlns="http://maven.apache.org/POM/4.0.0"

         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>

    <artifactId>book-api</artifactId>

    <version>1.0-SNAPSHOT</version>

    <properties>

        <maven.compiler.source>17</maven.compiler.source>

        <maven.compiler.target>17</maven.compiler.target>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

    </dependencies>

</project>

Step 2: Creating the Book Model

Next, create a sealed class for the book model. This allows for a defined class hierarchy where only designated classes can extend `Book`.

package com.example.model;



public sealed class Book permits Fiction, NonFiction {

    private final String title;

    private final String author;



    public Book(String title, String author) {

        this.title = title;

        this.author = author;

    }



    public String getTitle() {

        return title;

    }



    public String getAuthor() {

        return author;

    }

}



final class Fiction extends Book {

    public Fiction(String title, String author) {

        super(title, author);

    }

}



final class NonFiction extends Book {

    public NonFiction(String title, String author) {

        super(title, author);

    }

}

Step 3: Creating the REST Controller

Now, we'll develop a REST controller to manage HTTP requests related to books. This controller enables users to add and retrieve book information.

package com.example.controller;



import com.example.model.Book;

import com.example.model.Fiction;

import com.example.model.NonFiction;

import org.springframework.web.bind.annotation.*;



import java.util.ArrayList;

import java.util.List;



@RestController

@RequestMapping("/api/books")

public class BookController {

    private final List<Book> books = new ArrayList<>();



    @PostMapping

    public void addBook(@RequestBody Book book) {

        books.add(book);

    }



    @GetMapping

    public List<Book> getBooks() {

        return books;

    }

}

Step 4: Running the Application

Finally, create a main class to run the application:

package com.example;



import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;



@SpringBootApplication

public class BookApiApplication {

    public static void main(String[] args) {

        SpringApplication.run(BookApiApplication.class, args);

    }

}

Explanation of the Code

In this example, we developed a basic RESTful API using Spring Boot. The `Book` class is implemented as a sealed class, restricting inheritance to the `Fiction` and `NonFiction` classes. This design choice enhances type safety and maintainability.

The `BookController` class manages HTTP requests with two key methods: `addBook`, which allows users to add books, and `getBooks`, which retrieves all the books stored. This minimal API can be expanded further to include features like error handling, input validation, and data persistence.

Project Use Case-2: Data Processing with Streams

The enhanced Stream API in Java 17 allows for superior data processing capabilities. This is particularly beneficial for applications focused on data manipulation, such as reporting tools.

Example: Summing Even Numbers from a List

Consider a scenario where we need to process a list of integers to filter out even numbers and compute their total.

Step 1: Creating the Data Processing Class

import java.util.Arrays;

import java.util.List;



public class DataProcessor {

    public static void main(String[] args) {

        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);



        int sumOfEvens = numbers.stream()

                .filter(n -> n % 2 == 0)

                .mapToInt(Integer::intValue)

                .sum();



        System.out.println("Sum of even numbers: " + sumOfEvens);

    }

}

Explanation of the Code

In this example, the `DataProcessor` class handles a list of integers. The `stream()` method generates a stream from the list, while the `filter()` method isolates even numbers. The `mapToInt()` function transforms the stream into an `IntStream`, allowing the use of the `sum()` method to find the total.

This approach offers a clear and concise way to process data, leveraging the functional programming benefits in Java 17.

Thoughts

Java 17 introduces a range of new features and improvements that empower developers to build high-quality applications. From crafting RESTful APIs to efficiently processing data, the potential applications of Java 17 are significant.

By utilizing features like sealed classes and improved stream processing, developers can create powerful, maintainable applications tailored to modern demands. As Java evolves, it continues to be a vital and relevant programming language.

Whether you are an experienced Java developer or just starting out, exploring the new capabilities of Java 17 will boost your skills and enhance your projects. Leveraging these features can lead to clearer, more efficient, and maintainable code, ensuring your place in the fast-changing realm of software development.

Java 8 vs Java 11 vs Java 17: Feature Comparison

Feature / Aspect	Java 8 (2014)	Java 11 (2018, LTS)	Java 17 (2021, LTS)
LTS (Long-Term Support)	Yes	Yes	Yes
Release Type	Stable, widely adopted	Modernized, LTS	Most stable LTS with 8-year support
Syntax Enhancements	Lambdas, Streams, Optional, Default methods	var for local variables	Sealed classes, Pattern matching for switch, Records
HTTP Client API	Not available	New HTTP Client (replaces HttpURLConnection)	Standardized & stable
Garbage Collection (GC)	Parallel, CMS (default)	G1 as default	ZGC & Shenandoah (low-latency, production-ready)
JDK Size	Larger (JRE + JDK)	Modular (via Project Jigsaw in Java 9)	Smaller footprint, fully modular
Flight Recorder / Mission Control	Not available	Included (for profiling/monitoring)	Enhanced
New APIs	Stream API, Date-Time API (java.time)	String methods (isBlank(), lines(), repeat()), Files API improvements	Random Number Generator API, Foreign Function & Memory API (incubator)
Security	TLS 1.2 support	TLS 1.3 support, Stronger Cryptography	Strong encapsulation of internals, Security Manager deprecated
JRE Distribution	JRE & JDK	Only JDK (JRE removed)	Only JDK (smaller & modular)
Tooling	JavaFX included	JavaFX removed from JDK (separate library)	Consistent modular approach
Removed / Deprecated	PermGen space removed	Applet API deprecated	RMI Activation removed, Applet API deprecated further, Security Manager deprecated
Performance	Good	Better (compact strings, var handles, new GC)	Best (improved G1, ZGC, Shenandoah, faster startup)
Enterprise Adoption	Extremely high (still widely used)	Growing adoption	Strong adoption, preferred for migration

• If you are on Java 8, you’re missing out on performance, GC improvements, and modern language features.

• Java 11 is stable, but many features like pattern matching, sealed classes, and records are only in Java 17.

• Java 17 is the safest upgrade path because it is an LTS release with long support (till 2029) and gives the latest performance + security benefits.