Top Java 9 Features You Must Know

In this section, we will explore the top features introduced in Java 9 that every programmer should be familiar with. These new features will enhance your coding efficiency and keep you up-to-date in the ever-evolving technology world.

Key Takeaways:

• Java 9 introduces the module system, also known as Project Jigsaw, which allows for modular application development.
• JShell, an interactive Java Read-Eval-Print Loop (REPL) tool, makes it easier to experiment and test code snippets.
• Enhancements to the Stream API provide better control over stream processing.
• The Reactive Streams API enables asynchronous stream processing with non-blocking backpressure.
• Java 9 allows the declaration of private methods in interfaces, improving code reuse.

Module System (Project Jigsaw)

In Java 9, the introduction of the module system, also known as Project Jigsaw, revolutionizes the way we build and organize our Java applications. This powerful feature allows us to modularize our code by dividing it into separate modules.

With the Java 9 module system, we can achieve better encapsulation, making it easier to manage dependencies and ensure the integrity of our code. By organizing our application into modules, we can reduce the complexity and improve the maintainability of our codebase.

Additionally, the module system enhances the scalability and security of our Java applications. We can control which parts of our code are exposed to other modules, ensuring that our application is well-protected and optimized for performance.

The module system in Java 9 provides a structured approach to software development, enabling us to create more flexible and reliable applications. By embracing the module system, we can take our Java programming skills to the next level.

JShell – Interactive Java REPL

In the exciting world of Java programming, one of the standout features of Java 9 is the introduction of JShell, an interactive Java Read-Eval-Print Loop (REPL) tool. With JShell, we can experiment and test code snippets without the need for a full Java class or application, providing a more efficient and dynamic way to explore and learn the Java language.

JShell allows us to execute Java code snippets instantly, providing immediate feedback on their results. Gone are the days of writing lengthy test cases or creating separate Java applications just to test small pieces of code. With JShell, we can quickly validate our ideas and experiment with different coding approaches without the need for complex setup or compilation.

Let’s take a closer look at the power and convenience of JShell:

1. Instantaneous Code Execution: With JShell, we can execute code snippets as soon as we write them. Gone are the days of waiting for compiling and running a complete Java application. This instant feedback loop enables us to iteratively develop and test code more efficiently.
2. Interactive Exploration: JShell provides a flexible and interactive environment that allows us to explore the Java language and APIs. We can experiment with different concepts, test out new ideas, and quickly verify code behavior without the need for a separate development environment.
3. Incremental Development: JShell supports incremental development, meaning that we can build upon previously executed code snippets. This enables us to explore complex coding scenarios step by step and debug the code in real-time, enhancing our understanding of Java and improving our problem-solving skills.

Let’s take a look at a simple example:

JShell:

jshell> int result = 7 + 5;
  result ==> 12

In this example, we perform a basic arithmetic operation using JShell. We can see that the result of the addition is immediately displayed, eliminating the need for compilation and execution processes.

JShell also provides helpful features such as tab-completion and automatic variable declaration, making our coding experience even smoother. With these capabilities, JShell empowers us to quickly learn and experiment with the Java language in an interactive and intuitive way.

Now that we’ve explored the fascinating world of JShell, let’s move on to the next exciting feature introduced in Java 9.

Enhanced Stream API

In Java 9, the Stream API has undergone significant enhancements, providing developers with new methods for greater control and flexibility in stream processing. These improvements empower us to write more efficient and concise code when working with streams.

New Stream Methods

Java 9 introduces several new methods that expand the capabilities of the Stream API:

• takeWhile: This method allows us to take elements from a stream until a specific condition is met.
• dropWhile: With this method, we can exclude elements from a stream until a particular condition is satisfied.
• ofNullable: This method creates a stream that contains either a single element if it is non-null or no element if it is null.
• iterate: Enables us to generate an infinite stream by iteratively applying a function to the previous element.
• drop and take: These methods allow us to exclude or retrieve a specific number of elements from the beginning or end of a stream, respectively.

Optional Class Improvements

Java 9 also brings enhancements to the Optional class, making it more convenient and expressive when working with optional values:

• or: This method combines two Optionals and returns the first non-empty Optional, or an empty Optional if both are empty.
• ifPresentOrElse: With this method, we can specify separate actions to be executed when the Optional is present or when it is empty.

These enhancements to the Stream API and the Optional class enable us to write cleaner and more streamlined code for stream processing, improving our productivity as Java developers.

“The Enhanced Stream API in Java 9 provides powerful methods for manipulating streams, giving us more control over the data processing. These enhancements allow us to write more concise and efficient code, making our Java programs more robust and maintainable.”

Reactive Streams

In Java 9, we are introduced to the Reactive Streams API, which offers a standardized approach to handling asynchronous stream processing with non-blocking backpressure. This powerful API facilitates the management and processing of data streams that have the potential to overwhelm the system, ensuring smooth and efficient operation.

When dealing with data streams, particularly in scenarios where the incoming data rate exceeds the processing capacity, it is crucial to have mechanisms in place to handle these streams without causing bottlenecks or failures. The Reactive Streams API addresses this challenge by providing a set of interfaces, classes, and methods that allow developers to build reactive applications that can gracefully handle backpressure.

One of the key advantages of using the Reactive Streams API is its non-blocking nature, which allows for parallel and concurrent processing of data streams. This enables developers to optimize the performance and efficiency of their applications by utilizing the full processing power of the system.

By leveraging the Reactive Streams API in Java 9, developers can easily implement reactive and event-driven applications that can capitalize on the benefits of asynchronous and non-blocking programming. This empowers us to build highly scalable and responsive systems that can process high volumes of data without compromising performance.

The Reactive Streams API also promotes modularity and interoperability. It is designed to be compatible with other reactive frameworks and libraries, enabling seamless integration into existing projects and ecosystems. This compatibility ensures that developers can leverage the power of reactive programming without being limited to a specific framework or technology.

Private Methods in Interfaces

In Java 9, a new feature has been introduced that allows the declaration of private methods in interfaces. This enhancement provides interface authors with the flexibility to add private utility methods without affecting the existing implementations. Private methods in interfaces promote code reuse and improve the maintainability of the codebase.

Before Java 9, interfaces were limited to only having public and default methods. With the introduction of private methods, interface authors now have the ability to encapsulate common code logic within the interface itself, without exposing it to the implementing classes. This encapsulation helps in avoiding code duplication and promotes cleaner and more modular code.

Private methods in interfaces are primarily used to implement common utility methods that are used internally by the default methods of the same interface. With private methods, interface authors can now organize and structure their code more effectively, allowing for better readability and maintainability.

One of the key benefits of private methods in interfaces is that they provide a clear separation between the public API methods and the internal utility methods. This separation helps in maintaining a clean and cohesive interface design, making it easier for developers to understand and use the interface.

To demonstrate the usage of private methods in interfaces, consider the following example:

“By using private methods in interfaces, we can encapsulate common utility code and improve the overall design and maintainability of our codebase. This feature enables us to write cleaner and more modular code, leading to faster development and easier code reuse.”

By leveraging private methods in interfaces, developers can enhance their code architecture and improve the clarity and effectiveness of their interfaces. This feature empowers interface authors to create more robust and organized codebases that are easier to extend and maintain.

Next, let’s explore the enhancements made to the Process API in Java 9 and how they enable better control and management of native processes.

Process API Enhancements

In Java 9, the Process API undergoes significant enhancements, bringing better control and management capabilities for native processes. These advancements include new methods that enable monitoring and control of process resources, making it effortless to interact with operating system processes from within Java applications.

One of the notable additions is the introduction of the ProcessHandle class, which allows developers to access detailed information about running processes. With the ProcessHandle API, you can retrieve process IDs, check if a process is still running, and terminate a process gracefully.

Moreover, the Process API enhancements provide a standardized way to manage process resources, such as CPU and memory, through the ProcessHandle.Info class. This allows you to retrieve critical details about a process, including its command line arguments, environment variables, and resource usage metrics.

These improvements in the Process API impact various aspects of application development, from monitoring the performance of long-running processes to creating robust process management tools. By leveraging the enhanced Process API in Java 9, developers can optimize native process interactions and streamline their applications’ behavior.

Example: Monitoring Process Resource Usage

Let’s take a look at an example that demonstrates how the enhanced Process API in Java 9 can be used to monitor the resource usage of a running process:

// Get the process handle for the specified process ID

ProcessHandle processHandle = ProcessHandle.of(processId).orElseThrow(IllegalArgumentException::new);

// Get the information about the process handle

ProcessHandle.Info processInfo = processHandle.info().orElseThrow(IllegalStateException::new);

// Retrieve the command line arguments of the process

String[] commandLineArgs = processInfo.command().orElse(new String[0]);

// Retrieve the CPU usage of the process

double cpuUsage = processInfo.totalCpuDuration().orElse(Duration.ZERO).toNanos() / 1_000_000;

// Retrieve the resident set size (RSS) of the process

long residentSetSize = processInfo.residentSetSize().orElse(0L);

In the example above, we obtain the ProcessHandle for a specific process ID. We then retrieve various details about the process using the ProcessHandle.Info class, such as the command line arguments, CPU usage, and the resident set size (RSS).

These enhanced capabilities of the Process API in Java 9 empower developers to efficiently manage and monitor native processes within their Java applications, ensuring optimal performance and resource utilization.

Multi-Resolution Images

We are excited to announce that Java 9 introduces support for multi-resolution images, a powerful feature that enhances the visual experiences of your applications. With multi-resolution images, you can now store and load images at different resolutions, allowing your application to adapt seamlessly to various screen resolutions.

Whether your users are using high-density displays or lower resolution screens, multi-resolution images ensure that your application’s visuals are crisp and optimal. By providing images in multiple resolutions, you can offer a more immersive and tailored experience to your users, no matter what device they are using.

Let’s take a closer look at how multi-resolution images work and why they are valuable for your application development.

The power of multi-resolution images

Multi-resolution images enable your application to present the best possible visuals to users based on their device capabilities. Instead of relying on a single image file that may appear blurry or pixelated on certain screens, you can now provide high-resolution images for devices with high pixel density, while still optimizing file size and loading times for devices with lower resolutions.

This flexibility allows your application to deliver a seamless user experience across a wide range of devices, from smartphones and tablets to laptops and high-resolution displays.

Multi-resolution images empower developers to create visually stunning applications that maximize the potential of each device, delivering a consistent and engaging user experience. By taking advantage of this Java 9 feature, we can uplift the visual aesthetics and performance of our applications.

Implementation and usage

To utilize multi-resolution images in your Java 9 applications, you can leverage the MultiResolutionImage and MultiResolutionPixmap classes. These classes provide a structured way to handle images of different resolutions and enable you to choose the most suitable image for the user’s device dynamically.

By using the MultiResolutionImage or MultiResolutionPixmap, you can access and retrieve the available resolutions for an image and decide which resolution to use based on factors such as device DPI or user preferences.

With the ability to adapt to different screen resolutions, Java 9’s implementation of multi-resolution images empowers developers to provide a visually appealing and optimized user experience, no matter the device or display.

HTTP/2 Support

Java 9 brings built-in support for the HTTP/2 protocol, offering improved performance and efficiency in web communications. This exciting addition allows Java applications to leverage the latest web standards, delivering faster and more responsive web experiences.

Advantages of HTTP/2

• Enhanced Performance: HTTP/2 introduces various optimizations, including multiplexing and header compression, which significantly improve the overall performance of web applications.
• Efficient Resource Utilization: With HTTP/2, multiple requests can be sent concurrently over a single connection, reducing latency and optimizing resource utilization.
• Server Push: HTTP/2 enables servers to proactively send resources to the client before they are requested, eliminating the need for multiple roundtrips and improving page load times.
• Binary Protocol: HTTP/2 uses a binary protocol instead of plain text, reducing the complexity of parsing and making communication more efficient.

By leveraging Java 9’s built-in HTTP/2 support, developers can take advantage of these features and create high-performance web applications that provide seamless user experiences.

Streamlined JVM

Java 9 brings several key improvements to the Java Virtual Machine (JVM) that significantly enhance performance and efficiency. These optimizations include better memory management, faster startup times, and improved garbage collection algorithms. Let’s delve into each of these areas to understand the positive impact on Java application development.

Better Memory Management

Java 9 introduces advanced memory management techniques that optimize the allocation and deallocation of memory resources. The new metaspace replaces the traditional permanent generation, resulting in more efficient memory usage and decreased memory footprint. These improvements ensure that Java applications can handle large workloads and have reduced memory overhead.

Faster Startup Times

Java 9 addresses one of the primary concerns for Java application developers – startup times. With the introduction of the Ahead-of-Time (AOT) compilation option, Java applications can be pre-compiled into machine code, allowing for faster startup times and reduced initialization delays. This improvement is especially beneficial for applications that require quick response times, such as web servers and real-time systems.

Improved Garbage Collection Algorithms

Java 9 enhances the Garbage Collection (GC) algorithms, making them more efficient and predictable. The Garbage-First (G1) collector, which was introduced in Java 7, receives significant improvements in Java 9. The G1 collector optimizes garbage collection based on regions, resulting in more balanced and predictable pause times and improved overall application performance.

“Harnessing the power of the streamlined JVM in Java 9 allows us to build high-performing and efficient Java applications. With better memory management, faster startup times, and improved garbage collection algorithms, we can create applications that are optimized for speed and responsiveness.”

Improved Versioning Scheme

In Java 9, a new versioning scheme has been introduced, bringing a predictable pattern to the way Java libraries and applications are named. This improvement makes it easier to understand and track compatibility across different versions, greatly simplifying dependency management in Java projects.

Previously, Java versions were named using a complex combination of numbers, letters, and suffixes. This often made it challenging to determine the compatibility of libraries and applications, leading to potential issues during the development and deployment process.

With the new versioning scheme in Java 9, a simplified and consistent pattern has been adopted. Each version now follows a standard pattern of major version, minor version, and security/support version. This makes it easier for developers to understand the level of compatibility between different versions of Java libraries and applications.

For example, consider the following version numbers:

In the previous versioning scheme, there is no apparent pattern or indication of compatibility between the versions. However, in the new versioning scheme, it is clear that all versions belong to the same major version (9), indicating a higher level of compatibility.

This improved versioning scheme not only enhances the clarity of version numbers but also facilitates the identification of compatible libraries and applications. It enables developers to confidently manage dependencies in their Java projects, ensuring a smooth and error-free development process.

By adopting the new versioning scheme in Java 9, we can streamline development processes, improve compatibility tracking, and enhance the overall efficiency of Java projects.

Conclusion

Java 9 introduces a wide range of new features and improvements that empower developers to write better and more efficient code. With the module system (Project Jigsaw), programmers can now create modular applications, enhancing code organization and making it more scalable and secure. Furthermore, the JShell tool provides an interactive Java REPL, enabling developers to experiment and test code snippets with ease.

Enhancements in the Stream API offer better control over stream processing, while the introduction of Reactive Streams API simplifies asynchronous stream processing with non-blocking backpressure. Private methods in interfaces and improved Process API make code reuse and interaction with operating system processes more efficient.

Additional features, such as multi-resolution images that adapt to different screen resolutions and built-in support for the HTTP/2 protocol, further enhance the capabilities of Java applications. The streamlined JVM with better memory management and garbage collection algorithms ensures improved performance and efficiency. The improved versioning scheme simplifies the management of dependencies in Java projects.

Embrace the power of Java 9 and elevate your coding skills today. Explore these new features and improvements to stay ahead in the constantly evolving technology landscape.