Kotlin中的抽象类实现

abstract class Shape {
  init {
    println("执行Shape的初始化块......")
  }

  var color = ""
  abstract fun calPerimeter(): Double

  abstract val type: String

  constructor() {}

  constructor(color: String) {
    println("执行Shape的构造器...")
    this.color = color
  }
}

class Triangle(
  color: String, var a: Double,
  var b: Double, var c: Double
) : Shape(color) {
  fun setSides(a: Double, b: Double, c: Double) {
    if (a >= b + c || b >= a + c || c >= a + b) {
      println("三角形两边之和必须大于第三边")
      return
    }
    this.a = a
    this.b = b
    this.c = c
  }

  //重写Shape类的计算周长的抽象方法
  override fun calPerimeter(): Double {
    return a + b + c
  }

  //重写Shape类的代表形状的抽象属性
  override val type: String = "三角形"
}

class Circle(color: String, var radius: Double) : Shape(color) {
  override fun calPerimeter(): Double = 2 * Math.PI * radius

  override val type: String = "圆形"
}

fun main(args: Array<String>) {
  var s1: Shape = Triangle("黑色", 3.0, 4.0, 5.5)
  var s2: Shape = Circle("黄色", 4.0)
  println(s1.type)
  println(s2.type)

  println(s1.calPerimeter())
  println(s2.calPerimeter())
}

//定义带转速属性的主构造器
abstract class SpeedMeter(var turnRate: Double) {
  //把返回车轮半径的方法定义成抽象方法
  abstract fun calGirth(): Double

  //定义计算速度的通用算法
  fun getSpeed(): Double {
    //速度等于车轮周长*转速
    return calGirth() * turnRate
  }
}

public class CarSpeedMeter(var radius: Double) : SpeedMeter(0.0) {
  override fun calGirth(): Double {
    return radius * 2 * Math.PI
  }
}

fun main(args: Array<String>) {
  val csm = CarSpeedMeter(0.28)
  csm.turnRate = 15.0
  println(csm.getSpeed())
}

//定义一个密封类
sealed class Apple {
  abstract fun taste()
}

open class RedFuji : Apple() {
  override fun taste() {
    println("红富士苹果今年真贵，但是还是很甜。")
  }
}

data class Gala(var weight: Double) : Apple() {
  override fun taste() {
    println("嘎啦苹果也不便宜，但更清脆，重量为${weight}")
  }
}

fun main(args: Array<String>) {
  var ap1: Apple = RedFuji()
  var ap2: Apple = Gala(3.5)
  ap1.taste()
  ap2.taste()
}