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From Java 11 to Java 17 and Beyond Among other things José Paumard @JosePaumard Java Developer Advocate Java Platform Group

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https://twitter.com/JosePaumard https://github.com/JosePaumard https://www.youtube.com/user/java https://www.youtube.com/user/JPaumard https://www.youtube.com/hashtag/jepcafe https://fr.slideshare.net/jpaumard https://www.pluralsight.com/authors/jose-paumard https://dev.java

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 3 https://dev.java/

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 4 https://dev.java/community/

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 5 https://inside.java/

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 6 Java 17 – LTS! Java 8 Java 11

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 7 Java 17 – LTS! Java 8 Java 11 Java 17 ?

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 8 Next LTS: Java 21 Java 8 Java 11 Java 17 Java 21

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Language Type inference for locals (var) Switch expressions Text blocks Record classes Sealed classes Pattern matching for instanceof Compact String, Indify Concatenation JDK 17: New Features Since the JDK 8 Copyright © 2021, Oracle and/or its affiliates 9 Tools jshell jlink jdeps jpackage java source code launcher javadoc search + API history JVM Garbage Collectors: G1, ZGC AArch64 support: Windows, Mac, Linux Docker awareness Class Data Sharing by default Helpful NullPointerExceptions Hidden classes Libraries HTTP client Collection factories Unix-domain sockets Stack walker Deserialization filtering Pseudo-RNG, SHA-3, TLS 1.3

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 10 Stop doing that!

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 11 Do not call new Integer(...) Stop Calling Wrapper Classes Constructors! @Deprecated(since="9", forRemoval=true) public Integer(int value) { this.value = value; } @IntrinsicCandidate public static Integer valueOf(int i) { // some code return new Integer(i); }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 12 Do not override finalize() Stop Overriding Finalize! @Deprecated(since="9", forRemoval=true) protected void finalize() throws Throwable { }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 13 Strings

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 14 A new way of writing Strings Text Blocks String message = """ Hello world!""";

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 15 String Templates (prev.)

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 16 Interpolating strings from a template and variables String Templates (prev.) String name = "world"; String message = STR."Hello \{name}!"; System.out.println(message); > Hello world!

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 17 Is a String Template Expression STR is a template policy "Hello \{name}!" is a template with an embedded expression The evaluation produces a String, but not always String Template Expression String message = STR."Hello \{name}!";

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 18 Embedded expressions are expressions String Template Expression int x = 10, y = 20; String result = STR."\{x} + \{y} = \{x + y}"; System.out.println(result); > 10 + 20 = 30

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 19 Embedded expressions are expressions String Template Expression String result = STR."We have a \{getOfferType()} for you"; System.out.println(result); > We have a gift for you

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 20 Embedded expressions are expressions String Template Expression String time = STR."The time is \{ // The java.time.format package is very useful DateTimeFormatter .ofPattern("HH:mm:ss") .format(LocalTime.now()) } right now"; System.out.println(time); > The time is 12:34:56 right now

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 21 Embedded expressions are expressions String Template Expression int index = 10; String data = STR."\{index++} \{index++} \{index++}"; System.out.println(data); > 10 11 12

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 22 FMTR: formatter template policy More Template Policies String form = FMTR.""" Desc Unit Qty Amount %-10s\{description} $%5.2f\{price} %5d\{quantity} $%5.2f\{price * quantity} Subtotal $%5.2f\{price * quantity} Tax $%5.2f\{price * quantity * tax} Total $%5.2f\{price * quantity * (1.0 + tax)} """; System.out.println(form);

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 23 FMTR: formatter template policy More Template Policies Desc Unit Qty Amount hammer $ 7.88 3 $23.64 Subtotal $23.64 Tax $ 3.55 Total $27.19

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 24 Yes! A policy is a class that implements TemplatePolicy It supports validation to prevent injection It can return any object User Defined Policies?

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 25 Records

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 26 Short answer: a class! Less short answer: a class - That extends the Record class - That is final What is a Record?

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 27 And you can write: I Need to Write a Record! public record User(String name, int age) { } User sarah = new User("Sarah", 23); System.out.println(sarah); $ User[name=Sarah, age=23]

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 28 1) A constructor 2) Accessors: name() and age() 3) The following methods: toString(), equals(), hashCode() What Do you Get with a Record? public record User(String name, int age) { }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 29 You cannot extend a record A record cannot extend anything You cannot create any instance field in a record You can implement interfaces You can add any instance method You can add any static field or method Restrictions on Records

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 30 name and age are the components of the record Components are both final instance fields And accessors Components of a Record public record User(String name, int age) { }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 31 More on Components public record User(String name, int age) { } User user = new User("Sarah", 23); Class userClass = User.class; boolean isRecord = userClass.isRecord(); Component[] components = userClass.getRecordComponents();

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 32 More on Components public record User(String name, int age) { } User user = new User("Sarah", 23); RecordComponent nameComponent = components[0]; Class> declaring = nameComponent.getDeclaringRecord(); String name = (String) nameComponent.getAccessor()invoke(user);

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 33 More on Components public record User(@UserName String name, int age) { } @Target(ElementType.RECORD_COMPONENT) @interface UserName {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 34 The state of a record is entirely defined by its components - You cannot add more state by extension, or by extending anything - You cannot add any instance field Record State

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 35 The constructor of a record that takes its components is called the canonical constructor Record Building public record User(String name, int age) { public record User(String name, int age) { this.name = name; this.age = age; } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 36 Why would you write your own canonical constructor? 1) Defensive copy Record Building public record State(List cities) { public State(List cities) { this.cities = List.copyOf(cities); } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 37 In that case, you need to write your own accessor too! Record Building public record State(List cities) { public State(List cities) { this.cities = List.copyOf(cities); } public List cities() { return List.copyOf(cities); } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 38 Why would you write your own canonical constructor? 2) Validation Record Building public record Range(int begin, int end) { public Range(int begin, int end) { if (begin > end) { throw new IllegalArgumentException("..."); } this.begin = begin; this.end = end; } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 39 Why would you write your own canonical constructor? 2) Validation, with the Compact Constructor Record Building public record Range(int begin, int end) { public Range { if (begin > end) { throw new IllegalArgumentException("..."); } } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 40 A record constructor must call the canonical constructor Record Building public record Range(int begin, int end) { public Range(int end) { this.begin = 0; this.end = end; } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 41 A record constructor must call the canonical constructor Record Building public record Range(int begin, int end) { public Range(int end) { this(0, end); } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 42 You cannot build a record without calling its canonical constructor Deserialization calls the canonical constructor of a record

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 43 Deserialization calls the canonical constructor of a record Records are a perfect choice for Data Transport Objects Record Serialization

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 44 Sealed Types

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 45 Short answer: type (interface, class, abstract class)! Less short answer: a type - That declares its subtypes - That lives in the same package or module as them What is a Sealed Type?

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 46 A sealed type must declare its extension Syntax public sealed interface Shape permits Square, Rectangle, WeirdShape { }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 47 An extension of a sealed type must be: - final - or sealed - or non-sealed Syntax

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 48 An extension of a sealed type must be: - final Syntax public record Square(int edge) implements Shape { }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 49 An extension of a sealed type must be: - sealed Syntax public sealed class Rectangle permits ExtendedRectangle { }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 50 An extension of a sealed type must be: - non-sealed Syntax public non-sealed abstract class WeirdShape { }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 51 Pattern Matching

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?Record and Array Pattern Matching? Record Sealed Classes Switch Expression Constant Dynamic Inner Classes private in VM Nestmates Pattern Matching for instanceof 11 14 16 17 Switch on Types 19

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 53 In reference to the Amber Chronicles by Roger Zelazny Project Amber

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 54 A pattern is a combination of a match predicate that determines if the pattern matches a target, along with a set of pattern variables that are conditionally extracted if the pattern matches the target. Java 16 : Pattern Match for IntanceOf Pattern Matching for Java Gavin Bierman and Brian Goetz, September 2018 https://github.com/openjdk/amber-docs/blob/master/site/design-notes/pattern-matching-for-java.md

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 55 String name = the type of the pattern String = the name of the pattern name = the binding variable o = target operand Type Pattern if (o instanceof String name) { // some code }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 56 Type Pattern if (o instanceof String name) { Sytem.out.println(name.toUpperCase()); } if (o instanceof String name && name.length() > 0) { Sytem.out.println(name.toUpperCase()); }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 57 Type Pattern if (o instanceof String name) { Sytem.out.println(name.toUpperCase()); } if (!(o instanceof String name)) { // you cant use name here! return; // or throw an exception } Sytem.out.println(name.toUpperCase());

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 58 Record Pattern Matching (prev Java 19?)

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 59 Record Pattern Matching record User(String name, int age) {} if (o instanceof User user)) { String name = user.name(); int age = user.age(); }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 60 Record Pattern Matching record User(String name, int age) {} if (o instanceof User(String name, int age))) { // use name and age }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 61 Record Pattern Matching record User(String name, int age) {} if (o instanceof User(String name, int age) user)) { // use name and age }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 62 Record deconstruction is easy because a record is built on components And components are declared along with it The binding variables are initialized by calling the accessors Deconstructing a Record

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 63 Array Pattern Matching

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 64 Array Pattern Matching if (o instanceof String[] array && array.length() >= 2) { // do something with array[0] and array[1] }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 65 Array Pattern Matching if (o instanceof String[] {s1, s2}) { // do something with s1 and s2 }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 66 Nesting Patterns + Type Inference if (o instanceof Circle[] {Circle(var r1), Circle(var r2)}) { // do something with s1 and s2 } record Circle(int radius) {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 67 Nesting Patterns + Type Inference if (o instanceof Circle[] { Circle(Point(int x1, int y1), _), Circle(Point(int x2, int y2), _)}) { // do something with x1, y1, x2, y2 } record Circle(Point p1, int radius) {} record Point(int x, int y) {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 68 Pattern Matching for Switch

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 69 Pattern Matching for Switch interface Shape {} record Square(int edge) implements Shape {} record Circle(int radius) implements Shape {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 70 Pattern Matching for Switch double area(Shape shape) { return switch (shape) { case Square square -> square.edge()*square.edge(); case Circle circle -> Math.PI*circle.radius()* circle.radius(); default -> 0; } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 71 Switch on a Sealed Type sealed interface Shape permits Square, Circle {} record Square(int edge) implements Shape {} record Circle(int radius) implements Shape {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 72 Switch on a Sealed Type double area(Shape shape) { return switch (shape) { case Square square -> square.edge()*square.edge(); case Circle circle -> Math.PI*circle.radius()* circle.radius(); // default -> 0; // Not needed! } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 73 The compiler can: - check if a type is not present and raise an error - raise a warning if an uneeded default is present Switch on a Sealed Type

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 74 Guarded Pattern (prev. 17 and 18) double area(Shape shape) { return switch (shape) { case Square square && square.edge() == 0 -> 0; case Square square -> square.edge()*square.edge(); case Circle circle -> Math.PI*circle.radius()* circle.radius(); } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 75 Guarded Pattern (prev. 17 and 18) double area(Shape shape) { return switch (shape) { case Square square && square.edge() == 0 -> 0; case Square square -> square.edge()*square.edge(); case Circle circle -> Math.PI*circle.radius()* circle.radius(); } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 76 Switch Pattern with When (prev. 19?) double area(Shape shape) { return switch (shape) { case Square square when square.edge() == 0 -> 0; case Square square -> square.edge()*square.edge(); case Circle circle -> Math.PI*circle.radius()* circle.radius(); } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 77 (19 prev?) Switch and Record Pattern Matching double area(Shape shape) { return switch (shape) { case Square(int edge) when edge == 0 -> 0; case Square(int edge) -> edge*edge; case Circle(int radius) -> Math.PI*radius*radius; } }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | Confidential: Internal/Restricted/Highly Restricted 78 The Future of Pattern Matching

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 79 Nested Patterns, needed binding variables, type inference Syntaxic Sugars if (shape instanceof Circle(var center, _) && center instanceof Point(int x, int y)) { // center and radius are binding variables } if (shape instanceof Circle(Point(int x, int y), _)) { // center and radius are binding variables }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 80 The deconstruction uses the canonical constructor of a record What about: - factory methods? Deconstruction

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 81 Deconstruction Using Factory Methods interface Shape { static Circle circle(double radius) { return new Circle(radius); } static Square square(double edge) { return new Square(edge); } } record Circle(double radius) {} record Square(double edge) {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 82 Then this code could become possible: Deconstruction Using Factory Methods double area = switch(shape) { case Shape.circle(double radius) -> Math.PI*radius*radius; case Shape.square(double edge) -> edge*edge; }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 83 With factory methods Deconstruction Using Factory Methods if (opt instanceof Optional.of(var max)) { // max is a binding variable }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 84 With factory methods Deconstruction Using Factory Methods if (s instanceof String.format("%s is %d years old", String name, Integer.valueOf(int age) { // name and age are binding variables }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 85 Map deconstruction This is an extended form of Pattern Matching where you check the value of a binding variable Deconstruction Using Factory Methods if (map instanceof Map.withMapping("name", var name) && map instanceof Map.withMapping("email", var email)) { // name and email are binding variables }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 86 Pattern combination More Examples if (map instanceof Map.withMapping("name", var name) __AND Map.withMapping("email", var email)) { // name and email are binding variables } __AND = pattern combination

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 87 More Examples { "firstName": "John", "lastName": "Smith", "age": 25, "address" : { "street": "21 2nd Street", "city": "New York", "state": "NY", "postalCode": "10021" } } if (json instanceof stringKey("firstName", var firstName) __AND stringKey("lastName", var lastName) __AND intKey("age", var age) __AND objectKey("address", stringKey("street", var street) __AND stringKey("city", var city) __AND stringKey("state", var state) )) { // firstName, lastName, age, // street, city, state, ... // are binding variables }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 88 If Java Embraces « Map Literals » Map map = { "firstName": "John", "lastName": "Smith", "age": "25" } if (map instanceof { "firstName": var firstName, "lastName": var lastName, "age": Integer.toString(var age) }) { // firstName, lastName, age // are binding variables // age is a deconstructed int }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 89 The deconstruction uses the canonical constructor of a record What about: - factory methods? - classes that are not records? Deconstruction

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 90 What About Your POJOs? public class Point { private int x, y; public Point(int x, int y) { this.x = x; this.y = y; } public deconstructor(int x, int y) { x = this.x; y = this.y; } } This is the output of the deconstructor It allows both: - overloading - defensive copy

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 91 Match can check if an expression matches a pattern Just as if checks for a boolean expression Introducing Match

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 92 Pattern with Match (or Let?) record Point(int x, int y) {} record Circle(Point center, int radius) implements Shape {} Circle circle = ...; match Circle(var center, var radius) = circle; // center and radius are binding variables

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 93 Pattern with Let record Point(int x, int y) {} record Circle(Point center, int radius) implements Shape {} Circle circle = ...; let Circle(var center, var radius) = circle else throw new IllegalStateException("Not a circle");

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 94 Pattern with Let record Point(int x, int y) {} record Circle(Point center, int radius) implements Shape {} Circle circle = ...; let Circle(var center, var radius) = circle else { center = new Point(0, 0); // this is called radius = 0; // an anonymous matcher }

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 95 You can use match with more than one pattern… … or use nested patterns Pattern with Let Shape shape = ...; let Rectangle(var p1, var p2) = shape, Point(var x0, var y0) = p1, Point(var x1, var y2) = p2;

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 96 Nesting Patterns + Type Inference List points = ...; for (Point point: points) { int x = point.x(); int y = point.x(); // do something with x and y } record Point(int x, int y) {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 97 Nesting Patterns + Type Inference List points = ...; for (Point(int x, int y): points) { // do something with x and y } record Point(int x, int y) {}

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 98 • Constant Patterns: checks the operand with a constant value • Type Patterns: checks if the operand has the right type, casts it, and creates a binding variable Patterns at a Glance

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 99 • Patterns + Deconstruction: checks the operand type, casts it, bind the component to binding variables • Patterns + Method: uses a factory method or a deconstructor • Patterns + Var: infers the right type, and creates the binding variable • Pattern + _: infers the right type, but does not create the binding variable Patterns at a Glance

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5/1/2022 Copyright © 2021, Oracle and/or its affiliates | 100 Where are we? • Pattern Matching for instanceof (16) • Pattern Matching for Switch (prev 17, 18, 19?) • Record and Array Pattern Matching (19?) • Match • Literals Patterns at a Glance