FourteenApplication.java

package com.example.fourteen;

import lombok.extern.log4j.Log4j2;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.event.ApplicationReadyEvent;
import org.springframework.context.event.EventListener;
import org.springframework.util.Assert;

import java.util.Date;
import java.util.List;

@Log4j2
@SpringBootApplication
public class FourteenApplication {

	public static void main(String[] args) {
		SpringApplication.run(FourteenApplication.class, args);
	}

	@EventListener(ApplicationReadyEvent.class)
	public void go() {

		// multiline strings AND auto type inference
		var sql =
			"""
				  Would this work correctly if 
						I added it to a traditional 
						application?
				""".strip();

		log.info(sql);

		// convenient collection literals
		var listOfPeople = List.of(
			new Person("jlong", new Date()),
			new Person("rwinch", new Date())
		);

		// lambdas
		listOfPeople.forEach(person -> log.info(person.username()));
		// or method references!
		listOfPeople.forEach(log::info);

		// this pointer is (forcibly) Object so...
		var next = (Object) listOfPeople.iterator().next();

		// Let's use a smart cast...
		if (next instanceof Person p) {
			Date birthday = p.birthday();
			String username = p.username();
			log.info("this particular birthday is " + birthday);
			log.info("this particular username is " + username);
			log.info(p);
		}

		// switch expressions
		var dev = new Developer(Math.random() < .5 ? EmotionalState.NOT_WRITING_CODE : EmotionalState.WRITING_CODE);
		var message = switch (dev.currentStatus()) {
			case NOT_WRITING_CODE -> "Why wake up?";
			case WRITING_CODE -> "I love writing code!";
		};
		log.info(message);
	}
}

// still loving enums
enum EmotionalState {
	NOT_WRITING_CODE,
	WRITING_CODE
}

// records are like case classes or data classes in other languages
// records work just fine like this
record Developer(EmotionalState currentStatus) {
}

// or they can have 'compact' constructors
record Person(String username, Date birthday) {

	public Person {
		Assert.notNull(username, "the username is not null");
		Assert.notNull(birthday, "the birthday is not null");
		this.username = username.toUpperCase();
	}
}