Spark学习使用笔记 - Scala篇（3）- 对象

来源：互联网发布：cpu跑分软件编辑：程序博客网时间：2024/05/27 14:14

field

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  }}

Constructor

//main constructorclass 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  }}

练习：

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  }}

0 0