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Java 11 and 12 ??? New Features
Java 11 and 12 ??? New Features

Java 11 and 12 ??? New Features: Learn about Project Amber and the latest developments in the Java language and platform

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Paperback Mar 2019 242 pages 1st Edition
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Java 11 and 12 ??? New Features

Type Inference

The ability to use type inference with local variables (var) is one of the star features of Java 10. It reduces the verbosity of the language without compromising Java's dependable static binding and type safety. The compiler infers the type by using the information available in the code, and adds it to the bytecode that it generates.

Every new concept has its own set of benefits, limitations, and complexities. Using type inference with var is no exception. As you work through this chapter, using var will enthrall and frustrate you, but you will emerge triumphantly.

In this chapter, we'll cover the following topics:

  • What is type inference?
  • Type inference with var
  • Dos and don'ts of working with var
  • Type inference versus dynamic binding

What is type inference?

Imagine solving a riddle, such as the one shown in the following image, with multiple constraints in the form of hints. You resolve the constraints to derive the answer. You can compare type inference to generating constraints and then resolving them, in order to determine the data types in a programming language. Type inference is the capability of the compiler to determine the type of the data, by using the information that is already available in the code—literal values, method invocations, and their declarations. For a developer, type inference reduces verbosity, as indicated by the following diagram:

For your reference, the answer to the preceding riddle is 87 (just turn the image upside down, and you'll find the numbers in a sequence).

Type inference is not new to Java. It has been taken to the next level with the introduction of var...

Type inference with var

The following lines of code show how local variables (and all other variables) were defined prior to Java 10:

String name = "Java Everywhere"; 
LocalDateTime dateTime = new LocalDateTime.now();

Starting with Java 10, by using var, you can drop the mandatory explicit type in the declaration of local variables, as follows:

var name = "Java Everywhere";            // variable 'name' inferred as 
// String var dateTime = new LocalDateTime.now(); // var 'dateTime' inferred as
// LocalDateTime

Does it look like the preceding code doesn't offer a lot of benefits? Imagine you could take the following code:

HashMap<Integer, String> map = new HashMap<Integer, String>(); 

And replace it with this code, instead:

var map =...

Type inference in previous versions of Java

Although var takes inference to a new level in Java 10, the concept of type inference existed in Java's previous versions. Let's look at some examples of type inference in the previous versions of Java.

Type inference in Java 5

Generics introduced a type system to enable the developers to abstract over types. It restricted a class, interface, or method to working with instances of specified types, providing compile type safety. Generics were defined to add compile type safety to the Collections framework. Generics enable programs to detect certain bugs during compilation, so they can't creep into the runtime code.

Java used type inference for generic method type arguments...

Challenges

The use of var doesn't come without its share of challenges, for both the developers of the Java language and its users. Let's start with the reasons why var has limited usage.

Limiting the scope of failed assumptions

As you know, the use of var types is limited to local variables in Java. They are not allowed in the public API, as method parameters or as the return type of methods. Some languages support type inference for all types of variables. Java may allow us to do so in the future, but we don't know when.

However, there are strong reasons for limiting the scope of the inferred variables, to spot the errors due to mismatch of assumptions and the actual, early on. The contracts of the public...

Type inference versus dynamic binding

The use of type inference with var isn't pushing Java towards the dynamic binding domain. Java is still a strongly-typed static language. The type inference in Java is syntactic sugar. The compiler infers the type and adds it to the bytecode. In dynamic binding, a variable type is inferred at runtime. This can lead to more errors being discovered later.

Summary

In this chapter, we covered local variable inference, or var, as introduced in Java 10. The var type enables you to drop the explicit data type for a local variable in a method. We covered the various dos and don'ts for the usage of var. Limited to local variables, variables defined using var must be initialized with a value. They can be used with all types of variables—primitives and objects. Variables defined with var can also be passed to methods and returned from methods; method declaration compatibility rules apply.

To avoid risking your type safety with generics, ensure that you pass relevant information when using var with generics. Although it doesn't make a lot of sense, the use of explicit casting is allowed with variables defined using var.

We also covered ways in which type inference existed in previous versions of Java (5, 7, and 8). Toward...

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Key benefits

  • Overcome the challenges involved in migrating to new versions of Java
  • Discover how Oracle has bridged the gap between Java and native code
  • Make the best use of new Java features and libraries in your applications

Description

With its new six-monthly release cadence, Java is moving forward faster. In addition to planned version releases, a lot of work is currently being undertaken on various Java projects at Oracle. In order to make best use of the new features in their applications and libraries, you must be well-versed with the most recent advancements. Java 11 and 12 – New Features will take you through the latest developments in Java, right from variable type inference and simplified multithreading through to performance improvements, which are covered in depth to help you make your applications more efficient. This book explains the relevance and applicability of Java's new features, and answers your questions on whether to invest in migrating to new Java versions and when to migrate. You'll also get to grips with platform features, such as AppCDS and new garbage collectors, to tune and optimize your application—from reduced launch time and latency to improved performance and throughput. By the end of this book, you will be equipped with a thorough understanding of the new features of Java 11, 12, and Project Amber, and possess the skills to apply them with a view to improving your application's performance.

Who is this book for?

If you’re an executive or solutions architect responsible for technology selection or Java migration decisions, this Java book is for you. You’ll also benefit from this book if you’re a computer science enthusiast curious to learn about the latest and upcoming Java features. This book will help you migrate your solutions from Java 8 or older to the latest Java release.

What you will learn

  • Study type interference and how to work with the var type
  • Understand Class-Data Sharing, its benefits, and limitations
  • Discover platform options to reduce your application's launch time
  • Improve application performance by switching garbage collectors
  • Get up to date with the new Java release cadence
  • Define and assess decision criteria for migrating to a new version of Java

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Mar 26, 2019
Length: 242 pages
Edition : 1st
Language : English
ISBN-13 : 9781789133271
Vendor :
Oracle
Category :
Languages :

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Product Details

Publication date : Mar 26, 2019
Length: 242 pages
Edition : 1st
Language : English
ISBN-13 : 9781789133271
Vendor :
Oracle
Category :
Languages :

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Table of Contents

22 Chapters
Section 1: JDK 10 Chevron down icon Chevron up icon
Type Inference Chevron down icon Chevron up icon
AppCDS Chevron down icon Chevron up icon
Garbage Collector Optimizations Chevron down icon Chevron up icon
Miscellaneous Improvements in JDK 10 Chevron down icon Chevron up icon
Section 2: JDK 11 Chevron down icon Chevron up icon
Local Variable Syntax for Lambda Parameters Chevron down icon Chevron up icon
Epsilon GC Chevron down icon Chevron up icon
The HTTP Client API Chevron down icon Chevron up icon
ZGC Chevron down icon Chevron up icon
Flight Recorder and Mission Control Chevron down icon Chevron up icon
Miscellaneous Improvements in JDK 11 Chevron down icon Chevron up icon
Section 3: JDK 12 Chevron down icon Chevron up icon
Switch Expressions Chevron down icon Chevron up icon
Miscellaneous Improvements in JDK 12 Chevron down icon Chevron up icon
Section 4: Project Amber Chevron down icon Chevron up icon
Enhanced Enums in Project Amber Chevron down icon Chevron up icon
Data Classes and Their Usage Chevron down icon Chevron up icon
Raw String Literals Chevron down icon Chevron up icon
Lambda Leftovers Chevron down icon Chevron up icon
Pattern Matching Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon
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