Miroslav Wengner and Benedikt Neumayr will present on simplifying Java design patterns and new Java features. The agenda includes discussions of SOLID principles, design pattern types, simplifying object creation with builders and factories, structural patterns like adapter and flyweight, enforcing behavior at runtime with chains of responsibility and commands, touching on concurrency with thread pools, and concluding remarks. The presentation aims to improve code clarity, reduce verbosity, and enforce maintainability through Java language improvements and projects like Amber, Valhalla, and Loom.

1. Miroslav Wengner
New Java features
Simplified Design Patterns
Benedikt Neumayr

2. Safe Harbour Statement
All what you will hear can be di
ff
erent, this presentation is for
motivational purposes …

3. Miroslav Wengner
• Husband, Father, Software Engineer, Author, Blogger, Technology Enthusiast
• JCP: Executive Committee Board Member, OpenJDK Committer
• Java Mission Control Project, Open-Source projects
• Co-Author of Robo4J Project (Duke Award)
• Java Champion, JavaOne RockStar
• Principal Engineer at OpenValue

4. Benedikt Neumayr
• Human
• Managing Director at OpenValue
• Software Architect
• Expert for Project Consolidation
• Java Enthusiast

5. • Group Of Talented and Motivated Individuals
• Netherlands, Germany, Switzerland, Austria…
• Fun, Development, Trainings, Migration and
more…

6. Agenda
• Java Platform and OpenJDK
• SOLID thinking about design patterns
• Simplifying objects creation
• Thinking structural
• Enforcing behaviour at runtime
• Touching concurrency
• Conclusion
• Q/A

7. Java Platform and OpenJDK
• Compiler => byte-code
• JIT => instructions
• JVM Interpreter => EXPECTED RESULT
• Byte code optimisation: inlining, elimination, scalarization
static factory_method.Car produce(java.lang.String);
descriptor: (Ljava/lang/String;)Lfactory_method/Car;
fl
ags: (0x0008) ACC_STATIC
Code:
stack=7, locals=5, args_size=1
0: new #7 // class factory_method/FactoryMethodEvent
3: dup
…
19: aload_3
20: invokevirtual #17 // Method java/lang/String.hashCode:()I
23: lookupswitch { // 2
3135580: 48
3556498: 63
default: 75
}
48: aload_3
49: ldc #23 // String fast
51: invokevirtual #25 // Method java/lang/String.equals:(Ljava/lang/Object;)Z

8. SOLID thinking about design patterns
• SOLID principles:
• Single responsibility, Open-Close, Liskov Substitution
• Interface Segregation, Dependency Inversion
• Do NOT Repeat Yourself, Separation of Concerns, CAP
• Programming languages and technology agnostic
• Micro-services Architecture, Distributed systems
• Domain Driven Design, Data streaming (LM, AI)
• Extendability, Maintainability or Security
split?
More pieces there…
?
?

9. SOLID thinking about design patterns
• Design Pattern Types: Creational, Structural, Behavioural => Concurrency (services, runtime)
• Important projects
• Project Valhalla: performance gains through generic API, primitives and value types, ML and BigData apps
• Hidden Classes(JEP-371), Warnings for Value-Based Classes (JEP-390)…
• Project Panama: interconnecting JVM and well de
fi
ned non-java APIs, easier access for I/O apps
• Foreign Function & Memory API (JEP-424), Vector API (JEP-426)…
• Project Amber: improving productivity through Java language evolution
• Local-Variable Type inference (JEP-286), Switch Extension (JEP-361),
• TextBlocks (JEP-378), Records (JEP-395), Pattern Matching for instanceof (JEP-394)
• Sealed Classes (JEP-409), UTF-8 by Default(JEP-400), Record Patterns(JEP-405) …
• Project Loom: easy to use, hight-throughput, lightweight concurrency and programming approaches
• Virtual Threads (JEP-425), Structured Concurrency(JEP-428)…
?

10. Simplifying objects creation
• Candidates: Factory or Builder, what is the di
ff
erence ?
• wrapping or step by step till the end, complement, testable…
• Others:
Abstract Factory, Prototype, Singleton, Object pool
Lazy initialisation, Dependency Injection
?

11. Simplifying objects creation
Builder in JDK: StringBuilder or
public class Thread implements Runnable { //JDK19(Preview)
public sealed interface Builder
permits Builder.OfPlatform,
Builder.OfVirtual,
ThreadBuilders.BaseThreadBuilder {..}}
Factory in JDK: Java Collection framework: List, Set or Map
static <E> List<E> of(E e1, E e2, E e3) {
return ImmutableCollections.listFromTrustedArray(e1, e2, e3);
}
static <K, V> Map<K, V> of(K k1, V v) {
return new ImmutableCollections.Map1<>(k1, v1);
}
?

12. Simplifying objects creation
record FastCar(String type) implements Car {…
sealed interface Factory permits CarFactory {…
final class CarFactory {
static Vehicle produce(String type) {
var result = switch (type) {
case "fast" -> {
…
yield new FastCar(“super”);
}
case String s
when s.length() > 10 -> new SlowCar()
…
?

13. Thinking structural
• How to organise a code (instructions) around instantiated objects
• Candidates: Adapter, Flyweight
• Others: Composite, Decorator, Facade, Filter, Module, Front-
Module, Controller, Marker, Proxy, Twin
?

14. Thinking structural
Adapter in JDK:
public final class Spliterators {…
public static<T> Iterator<T> iterator(Spliterator<? extends T> spliterator) {
Objects.requireNonNull(spliterator);
class Adapter implements Iterator<T>, Consumer<T> {…}}}
public Collections {…
public static <T> ArrayList<T> list(Enumeration<T> e) {…}
Flyweight in JDK:
wrapper classes Integer, Byte, Character and valueOf(…) method uses Cache.
example: return IntegerCache.cache[i + (-IntegerCache.low)];
?

15. Thinking structural
?
var engine = counter++ % 2 == 0 ? new DieselEngine() : new ElectricEngine();
var fastCar = new FastCar(engine);
class FastCar {
…
FastCar(Engine engine){…}
public void drive(){
if (engine instanceof ElectricEngine ee) {
ee.checkBatteries();
}
engine.run();
…
sealed interface Engine {
void run();
}

16. Enforcing behaviour at runtime
• What about runtime?
• maintain information exchange between the objects
• Flexibility and maintainability: JVM and codebase
• Candidates: Chain of Responsibility, Command, Caching
• Others: State, Strategy , Interpreter, Iterator, Mediator, Memento,
Null Object, Observer, Pipeline, Template method, Visitor…
?

17. Enforcing behaviour at runtime
Chain of Responsibility in JDK
public class Logger {
public void log (Level level, Supplier<String> msgSupplier)
//overloaded method, Levels: OFF, SEVERE, WARNING …
Command in JDK:
java.lang.Runnable, java.lang.Callable
Caching in JDK
java.util.Locale
private static class Cache extends LocaleObjectCache<Object, Locale> {
private static final Cache LOCALECACHE = new Cache();
?

18. Touching concurrency
• What about code running in parallel?
• Multithreaded nature of the problem
• Design patterns combination…
• Candidate: Thread Pool Pattern
• Others: Active Object, Async Method Invocation, Balking,
Double-Checked Locking, Read-Write Lock, Scheduler …
?

19. Touching concurrency
?
var threadPerTaskExecutor = Executors.newThreadPerTaskExecutor(threadFactory);
var executor = Executors.newVirtualThreadPerTaskExecutor();
threadPerTaskExecutor.execute(() -> {
while (active.get()){
executor.submit(new ComputableTask(counter));
}
})
package dependency (JMC 8.3)

20. Conclusion
• Design Patterns and new JDK features helps to:
• improve code clarity: Sealed Classes, Pattern Matching
• reduce verbosity: Switch Statement improvements, Records
• enforce maintainability: Project Amber, Project Loom
• simpli
fi
ed composition: VirtualThreads, StructuredConcurrency, Switch, Local-Variable Type
• observability, pro
fi
ling, debugging and understanding
• Java as the 1st language for the JVM
?

21. Q / A
twitter: @openvalue
email: benedikt@openvalue.de
twitter: @miragemiko
github:@mirage22
email: miro@openvalue.de
Thank YOU !

22. References:
• Project Amber: https://openjdk.org/projects/amber/
• Project Valhalla: https://openjdk.org/projects/valhalla/
• Project Panama: https://openjdk.org/projects/panama/
• JFR Project: https://github.com/openjdk/jmc
• OpenJDK: https://openjdk.org/
• foojay.io: https://foojay.io/today/author/miro-wengner/
• OpenValue Blog: https://openvalue.blog/
Book In Progress: Practical Design Patterns for Java Developers [PACKT]