learning scala generic classes

package com.aura.scala.day01

object genericClasses {

  def main(args: Array[String]): Unit = {

    val stack = new Stack[Int]

    stack.push()

    stack.push()

    println(stack.pop())

    println(stack.pop())

  }

}

class Stack[A] {

  private var elements: List[A] = Nil

  def push(x: A){ elements = x :: elements }

  def peek():A = elements.head

  def pop():A = {

    val currentTop = peek()

    elements = elements.tail

    currentTop

  }

}

result:

"D:\Program Files\Java\jdk1.8.0_201\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA 2019.1.3\lib\idea_rt.jar=11061:D:\Program Files\JetBrains\IntelliJ IDEA 2019.1.3\bin" -Dfile.encoding=UTF- -classpath "D:\Program Files\Java\jdk1.8.0_201\jre\lib\charsets.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\deploy.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\access-bridge-64.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\cldrdata.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\dnsns.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jaccess.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jfxrt.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\localedata.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\nashorn.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunec.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunjce_provider.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunmscapi.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunpkcs11.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\zipfs.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\javaws.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jce.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jfr.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jfxswt.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jsse.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\management-agent.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\plugin.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\resources.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\rt.jar;C:\Users\admin\IdeaProjects\ScalaDay\out\production\ScalaDay;C:\Program Files (x86)\scala\lib\scala-actors-2.11.0.jar;C:\Program Files (x86)\scala\lib\scala-actors-migration_2.11-1.1.0.jar;C:\Program Files (x86)\scala\lib\scala-library.jar;C:\Program Files (x86)\scala\lib\scala-parser-combinators_2.11-1.0.4.jar;C:\Program Files (x86)\scala\lib\scala-reflect.jar;C:\Program Files (x86)\scala\lib\scala-swing_2.11-1.0.2.jar;C:\Program Files (x86)\scala\lib\scala-xml_2.11-1.0.4.jar" com.aura.scala.day01.genericClasses

实例对象 stack 只能接受整型值。然而，如果类型参数有子类型，子类型可以被传入：

class Fruit

class Apple extends Fruit

class Banana extends Fruit

val stack = new Stack[Fruit]

val apple = new Apple

val banana = new Banana

stack.push(apple)

stack.push(banana)

巴特西

learning scala generic classes

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