Project Amber

String json = "{\n"
	+ "\t\"name\": \"" + name + "\",\n"
	+ "\t\"year\": \"" + bday.getYear() + "\"\n"
	+ "}";

String duke = """
	{
		"name": "Duke",
		"year": "1992"
	}
	""";

String json = """
	{
		"name": "%s",
		"year": "%d"
	}
	""".formatted(name, bday.getYear());

String regex = "\\[\\d{2,4}\\]"; // 🤔🤔🤔
// made-up syntax!
String rawRegex = !"\[\d{2,4}\]" // 🤔

Predicate<Person> isOld = person -> person.age() >= 30;

var audienceMember = new Person("John Doe");

record Person(String name, LocalDate birthday) { }

if (obj instanceof Person person) {
	var name = person.name();
	var bday = person.birthday();
	// use `name` and `bday`
}

switch (obj) {
	case Person person -> {
		// as above...
	}
	// ...
}

if (obj instanceof Person(var name, var bday)) {
	// use `name` and `bday`
}

switch (obj) {
	case Person(var name, var bday) -> {
		// use `name` and `bday`
	}
	// ...
}

var person = fetchPerson();
var unnamed = new Person("", person.birthday());

var person = fetchPerson();
var unnamed = person with { name = ""; };

var person = fetchPerson();
var name = person.name();
var bday = person.birthday();
// use `name` and `bday`

// speculative syntax
Person(var name, var bday) = fetchPerson();
// use `name` and `bday`

public static Page loadPageTree(/*...*/) {
	// ...
}

public record ErrorPage(
	URI url, Exception ex) { }
public record ExternalPage(
	URI url, String content) { }
public record GitHubIssuePage(
	URI url, String content,
	Set<Page> links, int issueNumber) { }
public record GitHubPrPage(
	URI url, String content,
	Set<Page> links, int prNumber) { }

public sealed interface Page
		permits ErrorPage, SuccessfulPage {
	// ...
}

public sealed interface Page
        permits ErrorPage, SuccessfulPage {
    URI url();
}

public sealed interface SuccessfulPage
        extends Page permits ExternalPage, GitHubPage {
    String content();
}

public sealed interface GitHubPage
        extends SuccessfulPage
        permits GitHubIssuePage, GitHubPrPage {
    Set<Page> links();
    default Stream<Page> subtree() { ... }
}

public static String createPageName(Page page) {
	// ...
}

public static String createPageName(Page page) {
	return switch (page) {
		case ErrorPage err
			-> "💥 ERROR: " + err.url().getHost();
		case ExternalPage ext
			-> "💤 EXTERNAL: " + ext.url().getHost();
		case GitHubIssuePage issue
			-> "🐈 ISSUE #" + issue.issueNumber();
		case GitHubPrPage pr
			-> "🐙 PR #" + pr.prNumber();
		// ...
	};
}

switch (page) {
	case ErrorPage err -> // ...
	case ExternalPage ext -> // ...
	case GitHubIssuePage issue -> // ...
	case GitHubPrPage pr -> // ...
	// no default branch!
}

public static String createPageName(Page page) {
	return switch (page) {
		case ErrorPage(var url, var ex)
			-> "💥 ERROR: " + url.getHost();
		case GitHubIssuePage(
				var url, var content, var links,
				int issueNumber)
			-> "🐈 ISSUE #" + issueNumber;
		// ...
	};
}

public static String createPageName(Page page) {
	return switch (page) {
		case ErrorPage(var url, _)
			-> "💥 ERROR: " + url.getHost();
		case GitHubIssuePage(_, _, _, int issueNumber)
			-> "🐈 ISSUE #" + issueNumber;
		// ...
	};
}

public static String createPageEmoji(Page page) {
	return switch (page) {
		case GitHubIssuePage issue -> "🐈";
		case GitHubPrPage pr -> "🐙";
		case ErrorPage _, ExternalPage _ -> "n.a.";
	};
}

public class Main {
	public static void main(String[] args) {
		System.out.println("Hello, World!");
	}
}

java Prog.java

MyFirstJava
 ├─ Prog.java
 ├─ Helper.java
 └─ Lib
     └─ library.jar

java -cp 'Lib/*' Prog.java