Scala For Java的一些参考

变量	String yourPast = "Good Java Programmer";	val yourPast : String = "Good Java Programmer" val yourPast = "Good Java Programmer" var yourFuture = "Good Java Programmer" 自动类型推断；可变、不可变变量 class Money(amount:Int) amount不是成员变量 class Money(val amount:Int) val notMuch = new Money(2) notMuch.amount class Money(var amount:Int) val notMuch = new Money(2) notMuch.amount=3
case classes	public class Money { private Integer amount; private String currency; public Money(Integer amount, String currency) { this.amount = amount; this.currency = currency; } public Integer getAmount() { return amount; } public void setAmount(Integer amount) { this.amount = amount; } public String getCurrency() { return currency; } public void setCurrency(String currency) { this.currency = currency; } @Override public int hashCode() { int hash = 5; hash = 29 * hash + (this.amount != null ? this.amount. hashCode() : 0); hash = 29 * hash + (this.currency != null ? this.currency. hashCode() : 0); return hash; } @Override public boolean equals(Object obj) { if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final Money other = (Money) obj; return true; } @Override public String toString() { return "Money{" + "amount=" + amount + ", currency=" + currency + '}'; } public Money add(Money other) { return new Money(this.amount + other.amount, this.currency); } }	case class Money(amount:Int=1, currency:String="USD")  two immutable fields the fields declared in Scala classes are public case class Money(private val amount: Int, private val currency: String) to make them private instead, or used  var instead of  val to make the fields mutable. val defaultAmount = Money() val fifteenDollars = Money(15,"USD") val fifteenDollars = Money(15) val someEuros = Money(currency="EUR") case class Money(val amount:Int=1, val currency:String="USD"){ def +(other: Money) : Money = Money(amount + other.amount) } Money(12) + Money(34)
collections	Scala collections are, by default, immutable val numbers = List(1,2,3,4,5,6) val reversedList = numbers.reverse val onlyAFew = numbers drop 2 take 3 cons operator val numbers = 1 :: 2 :: 3 :: 4 :: 5 :: 6 :: Nil val simpleList = Nil.::(6) val twoElementsList = List(6).::(5) 列表串接 val concatenatedList = simpleList ::: twoElementsList val things = List(0,1,true) AnyVal val things = List(0,1,true,"false") Any 复杂对象列表 val amounts = List(Money(10,"USD"),Money(2,"EUR"),Money(20,"GBP"), Money(75,"EUR"),Money(100,"USD"),Money(50,"USD")) Filter val euros = amounts.filter(money => money.currency=="EUR") val euros = amounts.filter(x => x.currency=="EUR") val euros = amounts.filter(_.currency=="EUR") partition val allAmounts = amounts.partition(amt => amt.currency=="EUR") Tuples val euros = allAmounts._1 val everythingButEuros= allAmounts._2 val (euros,everythingButEuros) = amounts.partition(amt => amt.currency=="EUR")
Map	Map amounts = new HashMap<String,Integer>(); amounts.put("USD", 10); amounts.put("EUR", 2);	val wallet = Map( "USD" -> 10, "EUR" -> 2 ) val someEuros = wallet("EUR") Option类型 val mayBeSomePounds = wallet.get("GBP") val updatedWallet = wallet + ("GBP" -> 20)  新的不可变 val tenDollars = "USD"-> 10 Tuple
		def increment = (x:Int) => x + 1 List(1,2,3,4).map(increment) List(1,2,3,4) map increment
String Interpolation	val many = 10000.2345 val amount = s"$many euros" 格式化宽度 val amount = f"$many%12.2f euros" val amount = s"${many*2} euros" val printedAmounts = amounts map(m=> s"${m.amount} ${m.currency}")
groupBy	groupBy method that transforms a collection into a  Map collection: val sortedAmounts = amounts groupBy(_.currency)
Scala UnitTest	POM.xml maven依赖文件 •  Dependency for the core scala-library: <dependency> <groupId>org.scala-lang</groupId> <artifactId>scala-library</artifactId> <version>2.10.0</version> </dependency> •  Dependency for scalatest (a framework for testing in Scala that supports JUnit and other styles; we will cover it in detail in Chapter 4, Testing Tools): <dependency> <groupId>org.scalatest</groupId> <artifactId>scalatest_2.10</artifactId> <version>2.0/version> <scope>test</scope> </dependency> •  Dependency for JUnit to use Java  Assert statements in our test case: <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> scala-maven-plugin <plugin> <groupId>net.alchim31.maven</groupId> <artifactId>scala-maven-plugin</artifactId> <executions> <execution> <id>scala-compile-first</id> <phase>process-resources</phase> <goals> <goal>add-source</goal> <goal>compile</goal> </goals> </execution> <execution> <id>scala-test-compile</id> <phase>process-test-resources</phase> <goals> <goal>testCompile</goal> </goals> </execution> </executions> </plugin> 单元测试代码 import org.junit._ import Assert._ class CustomerScalaTest {   @Before   def setUp: Unit = {   }   @After   def tearDown: Unit = {   }   @Test   def testGetCustomerId = {     System.out.println("getCustomerId")     val instance = new Customer()     val expResult: Integer = null     val result: Integer = instance.getCustomerId()     assertEquals(expResult, result)   } }
Java/Scala Collection转换	./activator console import java.util.Arrays val javaList = Arrays.asList(1,2,3,4) import scala.collection.JavaConverters._ val scalaList = javaList.asScala val javaListAgain = scalaList.asJava assert( javaList eq javaListAgain)
JavaBean-style properties	class Company(var name:String) val sun = new Company("Sun Microsystems") sun.name sun.name_=("Oracle") import scala.beans.BeanProperty class Company(@BeanProperty var name:String) val sun = new Company("Sun Microsystems") sun.getName() sun.setName("Oracle")
OO	class Customer ( var customerId: Int, var zip: String) { def this( zip: String) = this(0,zip) def getCustomerId() = customerId def setCustomerId(cust: Int): Unit = { customerId = cust } } val customer = new Customer("123 45")
traits	interface VIPCustomer { Integer discounts(); } class Customer(val name:String, val discountCode:String="N" ){ def discounts() : List[Int] = List(5) override def toString() = "Applied discounts: " + discounts.mkString(" ","%, ","% ") } trait VIPCustomer extends Customer {   override def discounts = super.discounts ::: List(10) } trait GoldCustomer extends Customer { override def discounts =   if (discountCode.equals("H"))      super.discounts ::: List(20)   else super.discounts ::: List(15) } object Main { def main(args: Array[String]) { val myDiscounts = new Customer("Thomas","H") with VIPCustomer with GoldCustomer println(myDiscounts) } } scala> Main.main(Array.empty) Applied discounts: 5%, 10%, 20% Note that the order in which traits are stacked is important. They are calling each other from right to left.  GoldCustomer is, therefore, the first one to be called.
Static companion objects	object Main { def main(args: Array[String]) { println("Hello Scala World !") } } object Customer { def apply()= new Customer("default name") } class Customer(name:String) { … }
exceptions	public class ConversionSample { static Integer parse(String numberAsString) { Integer number = null; try { number = Integer.parseInt(numberAsString); } catch (NumberFormatExceptionnfe) { System.err.println("Wrong format for "+numberAsString); } catch (Exception ex) { System.err.println("An unknown Error has occurred"); } System.out.println("Parsed Number: "+number); return number; }	def parse(numberAsString: String) = try { Integer.parseInt(numberAsString) } catch { case nfe: NumberFormatException => println("Wrong format for number "+numberAsString) case e: Exception => println("Error when parsing number"+ numberAsString) } 返回值 case nfe: NumberFormatException => println("Wrong format for number "+numberAsString); -1 case _: Throwable => println("Error when parsing number "+numberAsString) -1 scala.util.Left or  scala.util.Right type case class Failure(val reason: String) def parse(numberAsString: String) : Either[Failure,Int] = try { val result = Integer.parseInt(numberAsString) Right(result) } catch { case _ : Throwable => Left(Failure("Error when parsing number")) }
	String customerLevel = null; if(amountBought > 3000) { customerLevel = "Gold"; } else { customerLevel = "Silver"; }	val amountBought = 5000 val customerLevel = if (amountBought> 3000) "Gold" else "Silver"
Scala的代码风格 IDE	http://docs.scala-lang.org/style/ Eclipse-based (including all the different versions of Eclipse, Typesafe's own bundled version known as Scala IDE as well as more commercial IDEs such as SpringSourceSTS), IntelliJ IDEA, and NetBeans.
SBT	Simple Build Tool (SBT) http://www.scala-sbt.org/ http://www.scala-sbt.org/0.13/tutorial/Hello.html 例子 http://www.scala-sbt.org/0.13/tutorial/Directories.html 目录结构，Build.sbt是sbt的定义文件
SBT plugins	https://github.com/typesafehub/sbteclipse 基于sbt生成eclipse使用的工程文件 https://github.com/mpeltonen/sbt-idea 基于sbt生成IntelliJ使用的工程文件 https://github.com/dcaoyuan/nbscala/wiki/SbtIntegrationInNetBeans 基于sbt生成Netbeans使用的工程文件   plugins.sbt中修改以生成 xsbt-web-plugin (available at  https://github.com/JamesEarlDouglas/xsbt-web-plugin ), a useful plugin to create traditional web apps that runs on a servlet container (such as Jetty). v Plugins.sbt： addSbtPlugin("com.earldouglas" % "xsbt-web-plugin" % "0.4.2") Build.sbt：   name := "SampleProject" organization := "com.samples" version := "1.0" scalaVersion := "2.10.3" seq(webSettings :_*) libraryDependencies += "org.mortbay.jetty" % "jetty" % "6.1.22" % "container" libraryDependencies += "javax.servlet" % "servlet-api" % "2.5" % "provided" v sbt eclipse生成了eclipse工程 v 启动web工程 > sbt > container:start v War包生成 > package
sbt-assembly	https://github.com/sbt/sbt-assembly v Plugins.sbt addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.11.2") v assembly.sbt import AssemblyKeys._ // put this at the top of the file assemblySettings // your assembly settings here
Scalariform	plugins.sbt addSbtPlugin("com.typesafe.sbt" % "sbt-scalariform" % "1.2.0") SBT中运行compile or  test:compile时，即按照scala风格格式化代码
Scala Worksheets	Eclipse中建立的菜单 每次保存时，可以看到执行的结果
Java基础库上scala的封装例子	http://dispatch.databinder.net/Dispatch.html HttpClient上的封装 build.sbt添加libraryDependencies += "net.databinder.dispatch" %% "dispatch-core" % "0.11.0" import dispatch._, Defaults._ val request = url("http://freegeoip.net/xml/www.google.com") val result = Http( request OK as.String) val resultAsString = result() def printer = new scala.xml.PrettyPrinter(90, 2) for (xml <- citiesAsXML) println(printer.format(xml))
for comprehension or  for expression	for (sequence) yield expression In the preceding code,  sequence can contain the following components: •  Generators: They drive the iteration and are written in the following form: element <- collection •  Filters: They control the iteration and are written in the following form: if expression •  Definitions: They are local variable definitions and are written in the following form: variable = expression for { elem <- List(1,2,3,4,5) } yield "T" + elem for { word <- List("Hello","Scala") char <- word } yield char.isLower for { word <- List("Hello","Scala") char <- word if char.isUpper } yield char or { word <- List("Hello","Scala") char <- word lowerChar = char.toLower } yield lowerChar
测试	ScalaTest ( www.scalatest.org ) and Specs2 ( etorreborre.github.io/specs2/ ). ScalaCheck framework ( www.scalacheck.org ) Typesafe Activator包含必要的插件，项目根下执行> activator eclipse即生成eclipse工程 import org.scalatest.FunSuite class Test01 extends FunSuite { test("Very Basic") { assert(1 == 1) } test("Another Very Basic") { assert("Hello World" == "Hello World") } } > activator > test-only scalatest.Test01 (or scalatest.Test01.scala) >~test-only scalatest.Test02  文件修改后自动运行单元测试【continuous mode】 The continuous mode works for the other SBT commands as well, such as  ~run or  ~test 作为Junit的单元测试方式运行 import org.junit.runner.RunWith import org.scalatest.junit.JUnitRunner import org.scalatest.FunSuite @RunWith(classOf[JUnitRunner]) class MyTestSuite extends FunSuite ... www.seleniumhq.org 功能测试 package scalatest import org.scalatest._ import org.scalatest.selenium.WebBrowser import org.openqa.selenium.htmlunit.HtmlUnitDriver import org.openqa.selenium.firefox.FirefoxDriver import org.openqa.selenium.WebDriver class Test08 extends FlatSpec with Matchers with WebBrowser { implicit val webDriver: WebDriver = new HtmlUnitDriver go to "http://www.amazon.com" click on "twotabsearchtextbox" textField("twotabsearchtextbox").value = "Scala" submit() pageTitle should be ("Amazon.com: Scala") pageSource should include("Scala Cookbook: Recipes") } www.scalamock.org
Web框架	alternatives to create web applications range from lightweight frameworks such as Unfiltered, Spray, or Scalatra to full-featured solutions such as the Lift or the Play Frameworks. http://www.playframework.com/ http://www.playmodules.net
Web Service	Plugins.sbt addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" %"2.4.0") addSbtPlugin("org.scalaxb" % "sbt-scalaxb" % "1.1.2") resolvers += Resolver.sonatypeRepo("public") build.sbt import ScalaxbKeys._ name:="wssample" scalaVersion:="2.10.2" scalaxbSettings ibraryDependencies += "net.databinder.dispatch" %% "dispatch-core" %"0.11.0" libraryDependencies += "org.scalatest" %% "scalatest" % "2.0.M7" %"test" sourceGenerators in Compile <+= scalaxb in Compile packageName in scalaxb in Compile := "se.wssample"
XML/JSON	val books = <Library> <book title="Programming in Scala" quantity="15" price="30.00" /> <book title="Scala for Java Developers" quantity="10" price="25.50" /> </Library> import scala.xml._ val sameBooks = XML.loadString(""" <Library> <book title="Programming in Scala" quantity="15" price="30.00"/> <book title="Scala for Java Developers" quantity="10" price="25.50"/> </Library> """) val total = (for { book <- books "book" price = ( book "@price").text.toDouble quantity = ( book "@quantity").text.toInt } yield price * quantity).sum val books = <Library> { List("Programming in Scala,15,30.00","Scala for Java Developers,10,25.50") map { row => row split "," } map { b => <book title={b(0)} quantity={b(1)} price={b(2)} /> }} </Library> import scala.util.parsing.json._ val result = JSON.parseFull(""" { "Library": { "book": [ { "title": "Scala for Java Developers", "quantity": 10 }, { "title": "Programming Scala", "quantity": 20 } ]} } """)
Futures and Promises	Scala Improvement Process (SIP)SIP-14-Futures and Promises http://en.wikipedia.org/wiki/Futures_and_promises •  async { <expression> } : In this construct,  <expression> is the code to be executed asynchronously. •  await { <expression returning a Future> } : This construct is included in an  async block. It suspends the execution of the enclosing  async block until the argument  Future is completed. async future Actor
Reactive Systems	http://www.reactivemanifesto.org/ 反应式编程
Misc	MongoDB database, we are going to discover how the Casbah Scala toolkit https://github.com/mongodb/casbah
	RPEL模式下拷贝部分代码运行 scala> :paste // Entering paste mode (ctrl-D to finish)