This is the presentation I was using in the meetup we delivered about Java15 new features. More info at https://www.meetup.com/lifemichael/events/275422829/ More information about our premium professional training services at https://lifemichael.com

1. What is new in Java 15
Haim Michael
April 12th
, 2021
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Table of Contents
 We are going to cover the following topics:
The JEP Process
Records
Sealed Classes
Hidden Classes
Patterns Matching
Foreign Memory Access
The ZGC JVM
The Shenandoah
Text Blocks

12. © 2008 Haim Michael 20150805
The JEP Process (JEP 0)
 The JEP process is the process of collecting, reviewing,
sorting and recording the results of proposals for the
enhancement of the JDK, and for related efforts.
 JEP stands for Java Enhancement Proposal. The JEP
process is defined by JEP 1.
https://openjdk.java.net/jeps

13. © 2008 Haim Michael 20150805
Records (JEP 384)
 The record is a new type of class. Using the 'record' keyword
(instead of 'class') we can easily create immutable data
objects.
public record Product(String name, int id) {
}

14. © 2008 Haim Michael 20150805
Records (JEP 384)
 The compiler infers which private instance variable should be
declared and auto generates toString, equals and
hashCode accordingly.

15. © 2008 Haim Michael 20150805
Records (JEP 384)
 We can add the definition for a constructor with validation
tests.
public record Product(String name, int id) {
public Product {
if(id<=0) {
//...
}
}
}

16. © 2008 Haim Michael 20150805
Records (JEP 384)
 The record we define is implicitly final, it cannot use native
methods and it cannot be declared abstract.

17. © 2008 Haim Michael 20150805
Sealed Classes (JEP 360)
 When defining a class as a sealed one we gain clear control
over the inheritance.
 In order to define a class as a sealed one we should add the
sealed keyword to the class definition. In addition, we should
add the permits keyword in order to specify which classes
can extend our sealed class.
 The class that extends a sealed class must be declared as a
sealed, non-sealed, or final.

18. © 2008 Haim Michael 20150805
Sealed Classes (JEP 360)
public sealed class Car permits SportCar, Bus {
//...
}
public final class Bus extends Car {
//...
}
public non-sealed class SportCar extends Car {
//...
}

19. © 2008 Haim Michael 20150805
Hidden Classes (JEP 371)
 As of Java 15, we can write code, that during its execution it
creates new hidden ones.
 The hidden classes are not discoverable. We cannot find
them using reflection.
 The hidden classes can be created using the ASP library.
More info about this library at https://asm.ow2.io/. More info
about how to create hidden classes using ASM, can be at
https://asm.ow2.io/

20. © 2008 Haim Michael 20150805
Patterns Matching (JEP 375)
 The patterns matching feature was introduced in Java 14.
This feature continues its preview status in Java 15 without
any enhancements.
 The current goal of is coming feature is to remove the
boilerplate code involved with the use of the instanceof
operator.

21. © 2008 Haim Michael 20150805
Patterns Matching (JEP 375)
Car car = new SportCar(true);
if(car instanceof SportCar sportCar) {
boolean sunRoof = sportCar.isTurbo();
//...
}

22. © 2008 Haim Michael 20150805
Patterns Matching (JEP 375)
 The future plan is to expand the support for patterns matching
to more features. It is strongly recommended to check out the
support for patterns matching in Scala in order to learn about
the possible features.

23. © 2008 Haim Michael 20150805
Foreign Memory Access (JEP 383)
 The foreign memory access was already available as an
incubating feature in Java 14. In Java 15, it continues to be in
its incubation status, while adding few more features.
 The foreign memory access feature allows us to access
memory outside of the heap managed by the JVM.

24. © 2008 Haim Michael 20150805
The ZGC JVM (JEP 377)
 As of Java 15, ZGC is no longer an experimental JVM. We
can start using it.
 ZGC excels in its support for large heap sizes with low
application pause times.

25. © 2008 Haim Michael 20150805
The Shenandoah (JEP 379)
 Shenandoah is an ultra-low pause time garbage collector. It
performs more garbage collection work concurrently with the
running program.
 As of Java 15 Shenandoah is no longer an experimental
feature.

26. © 2008 Haim Michael 20150805
Text Blocks (JEP 379)
 The support for text blocks is available as an experimental
feature as of Java 13. As of Java 15, the use of text blocks is
no longer experimental.
String text = """
<html>
<head>
<title>We Love Java!</title>
</head>
<body>
<h1>Java is Awesome!</h1>
</body>
</html>
""";

27. © 2008 Haim Michael 20150805
Text Blocks (JEP 379)
 The text we don't need to escape “ (double quotes). We can
add them without any escaping.
String text = """
we love Java "it is awesome!"
""";

28. © 2008 Haim Michael 20150805
Text Blocks (JEP 379)
 The String.formatter(parameter) method was added in order
to assist us with variables substitutions.
String text = """
We Love %s
%s is Awesome!
""".formatted("Java","Kotlin");

29. © 2009 Haim Michael All Rights Reserved 29
Questions & Answers
Thanks for Your Time!
Haim Michael
haim.michael@lifemichael.com
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