Spark学习使用笔记 - Scala篇（5）- 继承

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继承override

//覆盖父类的field或者方法一定要加overrideclass 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

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varclass 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)  }}

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