Spark学习使用笔记 - Scala篇（3）- 对象

class Counter {
  //field必须初始化，为了知道类型
  //会自动生成private的getter还有private的setter
  //setter和getter并不是getValue()和setValue()这样，而是value(),value_=()这样
  private var value = 0

  def increment() = {
    value += 1
  }

  def current() = value

  //类私有field可以访问
  def largerThan(a: Counter): Boolean = {
    value > a.value
  }

  //对象私有field别的对象无法访问
  private[this] var name = "test"

  def setName(name: String) = {
    this.name = name
  }

  //会自动生成public的getter和setter
  var times = 0
  //会自动生成public的getter
  val alloc = "hash"

}

object Counter1 {
  val counter = new Counter
  def testClass = {
    //习惯上取值器不加括号
    println(counter.current)//输出：0
    //习惯上改值器加括号
    counter.increment()
    println(counter.current)//输出：1

    val counter2 = new Counter
    println(counter.largerThan(counter2))//输出：true
  }
}

//main constructor
class Person(val name: String, var age: Int, var salary: Int) {
  //主构造器会执行所有语句
  println("Main constructor is called!")

  //多态构造器
  def this(name: String, age: Int) {
    this(name, age, 0)
  }

  def description = "Name: " + name + ", Age: " + age + ", Salary: " + salary
}

object Person1 {
  def test = {
    val person = new Person("zhxhash", 24, 20000)//输出：Main constructor is called!
    println(person.description)//输出：Name: zhxhash, Age: 24, Salary: 20000

    val person2 = new Person("zhxdick", 15)//输出：Main constructor is called!
    println(person2.description)//输出：Name: zhxdick, Age: 15, Salary: 0
  }
}

object Exercise {

  class Counter(private var value: Int = 0) {
    def increment() = {
      if (value == Int.MaxValue)
        value = 0
      else
        value += 1
    }

    def current = value
  }

  def ex01 = {
    val counter = new Counter(Int.MaxValue)
    counter.increment()
    println(counter.current)//输出：0
  }

  class BankAccount(private var balance: Double) {
    def currentBalance = balance

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

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

  def ex02 = {
    val bankAccount = new BankAccount(100000)
    bankAccount.deposit(99)
    bankAccount.withdraw(88)
    println(bankAccount.currentBalance)//输出：100011.0
  }

  class Time(private val hours: Int, private val minutes: Int) {
    if (hours < 0 || hours > 23 || minutes < 0 || minutes > 59)
      throw new IllegalArgumentException()

    def before(other: Time): Boolean = {
      (hours > other.hours) || ((hours == other.hours) && (minutes > other.minutes))
    }

    def description = "[" + hours + ":" + minutes + "]"
  }

  def ex03 = {
    val time = new Time(13, 59)
    val time2 = new Time(13, 25)
    val time3 = new Time(14, 25)

    println(time.description + time2.description + time.before(time2))//输出：[13:59][13:25]true
    println(time.description + time3.description + time.before(time3))//输出：[13:59][14:25]false
  }
}