Java 8/11/17 Features

Most Important Java 8 Features

• Lambda

List<String> names = List.of("A", "B", "C");

names.forEach(name -> System.out.println(name));

• Streams

List<String> result = names.stream()
                           .filter(n -> n.startsWith("A"))
                           .toList();

• Optional

Optional<User> user = repository.findById(1L);

• CompletableFuture

@Async
public CompletableFuture<String> process() {
    return CompletableFuture.completedFuture("Done");
}

• Functional Interfaces

@FunctionalInterface
interface Calculator {
    int add(int a, int b);
}

Common interfaces:

• Predicate<T>
• Function<T,R>
• Consumer<T>
• Supplier<T>

Most Important Java 11 Features

• HttpClient

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HttpClient client = HttpClient.newHttpClient();

HttpRequest request =
    HttpRequest.newBuilder()
               .uri(URI.create("https://api.com"))
               .build();

HttpResponse<String> response =
    client.send(request,
                HttpResponse.BodyHandlers.ofString());

• String API Enhancements
• Files API

String content =
    Files.readString(path);

Files.writeString(path, content);

Most Important Java 17 Features

• Records

public record User(
        String name,
        int age
) {}

Automatically generates:
Constructor
Getters
equals()
hashCode()
toString()

• Sealed Classes

Only permitted subclasses can extend.

public sealed class Shape
    permits Circle, Rectangle {
}

• Pattern Matching

if(obj instanceof String s) {
    System.out.println(s.length());
}

• Switch Expressions

return switch(day) {
    case MONDAY -> 1;
    default -> 0;
};

Java 8, 9, 10, 11, and 17 features:

Most Important of Java 8/11/17