构造函数 #

class Person(name: String, age: Int):
  def greet(): String = s"Hello, I'm $name, $age years old"

val person = Person("Alice", 25)
println(person.greet())

class Person(
  val name: String,
  var age: Int,
  private val id: String
):
  def info: String = s"$name (ID: $id)"

val person = Person("Alice", 25, "P001")
println(person.name)
person.age = 26

class Person(
  val name: String = "Unknown",
  val age: Int = 0
)

val p1 = Person()
val p2 = Person("Alice")
val p3 = Person("Bob", 25)
val p4 = Person(age = 30)

class Person(name: String, age: Int):
  println(s"Creating person: $name")
  
  val birthYear: Int = java.time.Year.now.getValue - age
  
  def greet(): String = s"Hello, I'm $name, born in $birthYear"

val person = Person("Alice", 25)
println(person.birthYear)

class DatabaseConnection(url: String):
  println(s"Connecting to $url...")
  
  private val connection = connect()
  
  private def connect(): Connection =
    println("Connection established")
    ???
  
  def query(sql: String): Result = ???
  
  def close(): Unit =
    println("Closing connection...")
    ???

class HeavyResource(path: String):
  lazy val data: String =
    println("Loading data...")
    scala.io.Source.fromFile(path).mkString
  
  def process(): String =
    s"Processing: ${data.take(100)}"

val resource = HeavyResource("data.txt")
println("Created")
resource.process()

class Person(val name: String, val age: Int):
  def this(name: String) = this(name, 0)
  def this() = this("Unknown")

val p1 = Person("Alice", 25)
val p2 = Person("Bob")
val p3 = Person()

class Rectangle(val width: Double, val height: Double):
  def this(size: Double) = this(size, size)
  def this() = this(1.0)
  
  def area: Double = width * height
  def isSquare: Boolean = width == height

val r1 = Rectangle(10, 20)
val r2 = Rectangle(5)
val r3 = Rectangle()

class Date(val year: Int, val month: Int, val day: Int):
  def this(year: Int, dayOfYear: Int) =
    this(year, 1, 1)
  
  def this(timestamp: Long) =
    this(1970, 1, 1)

val d1 = Date(2024, 3, 27)
val d2 = Date(2024, 86)
val d3 = Date(System.currentTimeMillis())

class Singleton private ():
  def doSomething(): String = "Working..."

object Singleton:
  private val instance = Singleton()
  def getInstance: Singleton = instance

val singleton = Singleton.getInstance

class Person private (val name: String, val age: Int)

object Person:
  def apply(name: String, age: Int): Person = new Person(name, age)
  def child(name: String): Person = new Person(name, 0)
  def adult(name: String): Person = new Person(name, 18)
  def unknown: Person = new Person("Unknown", 0)

val p1 = Person("Alice", 25)
val p2 = Person.child("Bob")
val p3 = Person.adult("Charlie")
val p4 = Person.unknown

class Config private (val settings: Map[String, String]):
  private def this() = this(Map.empty)

object Config:
  def fromFile(path: String): Config =
    val settings = scala.io.Source.fromFile(path)
      .getLines()
      .map(_.split("=", 2))
      .map(arr => arr(0) -> arr(1))
      .toMap
    Config(settings)
  
  def default: Config = Config(Map("timeout" -> "5000"))

val config = Config.fromFile("config.properties")
val defaultConfig = Config.default

class Person(name: String, age: Int):
  def greet(): String = s"$name, $age"
  
val person = Person("Alice", 25)

class Person(val name: String, val age: Int)

val person = Person("Alice", 25)
println(person.name)

class Person(var name: String, var age: Int)

val person = Person("Alice", 25)
person.name = "Bob"
person.age = 26

class Person(private val name: String, private val age: Int):
  def info: String = s"$name, $age"

val person = Person("Alice", 25)
println(person.info)

class Animal(protected val name: String)

class Dog(name: String) extends Animal(name):
  def bark(): String = s"$name says: Woof!"

val dog = Dog("Rex")
println(dog.bark())

class Animal(val name: String):
  def speak(): String = "Some sound"

class Dog(name: String, val breed: String) extends Animal(name):
  override def speak(): String = s"$name says: Woof!"

val dog = Dog("Rex", "German Shepherd")
println(dog.speak())
println(dog.breed)

class Vehicle(val brand: String, val year: Int)

class Car(brand: String, year: Int, val model: String) 
  extends Vehicle(brand, year):
  def info: String = s"$brand $model ($year)"

val car = Car("Toyota", 2024, "Camry")
println(car.info)

class A(val x: Int)
class B(x: Int, val y: Int) extends A(x)
class C(x: Int, y: Int, val z: Int) extends B(x, y):
  def sum: Int = x + y + z

val c = C(1, 2, 3)
println(c.sum)

class Person(val name: String, val age: Int)

class Person(name: String, age: Int):
  val _name = name
  val _age = age

class Person(val name: String = "Unknown", val age: Int = 0)

class Person(val name: String, val age: Int):
  def this(name: String) = this(name, 0)
  def this() = this("Unknown")

class Connection private (val host: String, val port: Int)

object Connection:
  def apply(host: String, port: Int): Connection = 
    new Connection(host, port)
  
  def localhost(port: Int = 8080): Connection = 
    new Connection("localhost", port)
  
  def fromUrl(url: String): Connection =
    val uri = java.net.URI(url)
    new Connection(uri.getHost, uri.getPort)

val c1 = Connection("example.com", 80)
val c2 = Connection.localhost()
val c3 = Connection.fromUrl("http://api.example.com:8080")

class Person(val name: String, val age: Int):
  require(name.nonEmpty, "Name cannot be empty")
  require(age >= 0 && age <= 150, "Age must be between 0 and 150")

Person("Alice", 25)
Person("", 25)
Person("Bob", 200)