Spark学习使用笔记 - Scala篇（5）- 继承

继承override

代码语言：javascript复制

//覆盖父类的field或者方法一定要加override
class BankAccount(val initialBalance: Double) {
  private var balance = initialBalance

  def deposit(value: Double) = {
    balance  = value
    balance
  }

  def withdraw(value: Double) = {
    balance -= value
    balance
  }
}

class CheckingAccount(override val initialBalance: Double) extends BankAccount(initialBalance) {
  private var balance = initialBalance

  override def deposit(value: Double) = {
    balance -= 1
    balance  = value
    balance
  }

  override def withdraw(value: Double) = {
    balance -= 1
    balance -= value
    balance
  }
}

class SavingAccount(override val initialBalance: Double) extends BankAccount(initialBalance) {
  private var balance = initialBalance

  private var freeProcess = 3

  private val monthlyInterestRate = 0.01

  private def checkFreeProcess = {
    if (freeProcess > 0) {
      freeProcess -= 1
      false
    } else {
      true
    }
  }

  private def earnMonthlyInterest = {
    freeProcess = 3
    balance  = balance * monthlyInterestRate
    balance
  }

  override def deposit(value: Double) = {
    if (checkFreeProcess)
      balance -= 1
    balance  = value
    balance
  }

  override def withdraw(value: Double) = {
    if (checkFreeProcess)
      balance -= 1
    balance -= value
    balance
  }

抽象

代码语言：javascript复制

abstract class Item {
  //抽象filed和method不用abstract修饰
  def price: Double

  def description: String


}

//def只能重写另一个def
//val可以重写另一个val还有def
//var只能重写另一个抽象var
class SimpleItem(val price: Double, val description: String) extends Item {
  override def toString = {
    "["   description   ":"   price   "]"
  }
}

class Bundle extends Item {
  private val items = ArrayBuffer[Item]()

  def addItems(item: Item) = {
    items  = item
    items
  }

  def price = {
    var amount = 0.0;
    for (i <- items) {
      amount  = i.price
    }
    amount
  }

  def description = {
    items.mkString("")
  }
}

object Item{
  def test = {
    val item1 = new SimpleItem(9.9,"pencil")
    val item2 = new SimpleItem(99.9,"pen")
    val items = new Bundle
    items.addItems(item1)
    items.addItems(item2)
    println(items.description)
  }
}

继承

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