println("Step 1: How to create a wrapper String class which will extend the String type") class DonutString(s: String) { def isFavoriteDonut: Boolean = s == "Glazed Donut" } println("\nStep 2: How to create an implicit function to…

Scala collection such as List or Sequence or even an Array to variable argument function using the syntax :_ *. code : def printReport(names: String*) { println(s"""Donut Report = ${names.mkString(" - ")}""") } prin…

package com.example import akka.actor.ActorSystem import scala.util.{Failure, Success} import scala.concurrent.ExecutionContext.Implicits.global object Tutorial_01_ActorSystem_Introduction extends App { println("Step1 : Create an actor system")…

用maven打包写好的jar,在放到hive中作暂时函数时报错. 错误信息例如以下: hive> create temporary function maxvalue as "com.leaf.data.Maximum"; java.lang.SecurityException: Invalid signature file digest for Manifest main attributes at sun.security.util.SignatureFileVerifier…

表分区的操作三步走: 1.创建分区函数 CREATE PARTITION FUNCTION xx1(int) 解释:在当前数据库中创建一个函数,该函数可根据指定列的值将表或索引的各行映射到分区. 语法: CREATE PARTITION FUNCTION partition_function_name ( input_parameter_type ) AS RANGE [ LEFT | RIGHT ] FOR VALUES ( [ boundary_value [ ,...n ] ] ) [ ;…

package com.example import akka.actor._ import akka.util.Timeout object Tutorial_03_Ask_Pattern extends App { val system = ActorSystem("DonutStoreActorySystem") val donutInfoActor = system.actorOf(Props[DonutInfoActor], name="DonutInfoActor…

目录 4.1 The Inverse Function Theorem The Implicit Function Theorem 4.3 Curves and Surfaces 4.4 The Morse Lemma Chapter 4 Inverse Function Theorem 这个章节讲得很好, 还引用了庄子秋水中的一段话, 大佬啊. 4.1 The Inverse Function Theorem 映射\(F: \mathbb{R}^n \rightarrow \mathbb{R}…

隐式类可以用来扩展对象的功能非常方便 example: object ImplicitClass_Tutorial extends App { println("Step 1: How to define a case class to represent a Donut object") case class Donut(name: String, price: Double, productCode: Option[Long] = None) println("\nSte…

可以使用scala库,可以从字面上看出是在调用 递归函数: code import scala.util.control.TailCalls._ val arrayDonuts: Array[String] = Array("Vanilla Donut", "Strawberry Donut", "Plain Donut", "Glazed Donut") println("\nStep : How to defin…

Ordering using andThen: f(x) andThen g(x) = g(f(x)) Ordering using compose: f(x) compose g(x) = f(g(x)) println("Step 1: Assume a pre-calculated total cost amount") val totalCost: Double = println("\nStep 2: How to define a val function to…

一. Implicit关键字 隐士转换 (1)隐士转换函数:用implicit修饰的,只有一个参数的函数.他会被自动执行,来把一个值转换成另一个 class RichFile(val f:File){ def read = Source.fromFile(f).mkString } implicit def file2richFile(f:File) = new RichFile(f) //隐士转换函数 val result: String = new File("/home/lj/chrome…

1.for循环是一个循环控制结构,可以有效地编写需要执行的特定次数的循环.Scalar的循环说明如下的各种形式: 1)Scala中for循环最简单的语法是: for( var x <- Range ){ statement(s); } 在这里,范围可能是一个数字范围,并且表示为i到j或有时像i到j左箭头 < - 操作者被称为生成器,这样命名是因为它是从一个范围产生单个数值. 2)for循环中,循环将遍历给定范围内的所有可能的计算,可以使用分号 (;) 分隔多个范围.下面是使用两个范围的例子,也…

文章正文 通过隐式转换,程序员可以在编写Scala程序时故意漏掉一些信息,让编译器去尝试在编译期间自动推导出这些信息来,这种特性可以极大的减少代码量,忽略那些冗长,过于细节的代码. 1.Spark 中的隐式思考 隐式转换是Scala的一大特性, 如果对其不是很了解, 在阅读Spark代码时候就会很迷糊,有人这样问过我? RDD这个类没有reduceByKey,groupByKey等函数啊,并且RDD的子类也没有这些函数,但是好像PairRDDFunctions这个类里面好像有这些函数 为什么我可…

--书藉位置Place目录 drop table BookPlaceList; create table BookPlaceList ( BookPlaceID INT PRIMARY KEY, --NUMBER BookPlaceName nvarchar2(500) not null, BookPlaceCode varchar(100) null, --位置編碼 BookPlaceParent INT null --BookPlaceKindId nvarchar(500) null --…

create database Liber; use Liber; #顯示數据庫 20150210 Geovin Du 涂聚文 SHOW DATABASES; drop table BookKindList; #书目录 create table BookKindList ( BookKindID INT NOT NULL AUTO_INCREMENT, #自动增加 BookKindName nvarchar(500) not null, BookKindParent int null, PRIM…

1.for的使用 for的使用在各种编程语言中是最常见的,这里只是聊聊for在Scala中的表现形式,由于Scala语言是完全面向对象的,所以直接导致for的不同呈现,下面举几个例子说明一下 object For { def main(args:Array[String]):Unit={ for(i<-1 to 2;j<-1 to 2) println("i is:"+i+"   j is:"+j) println("-------------…

implicit 分为隐式转换和隐式参数,下面例子展现了两种方式的用法: package com.citi.scala class Man(val name: String) { def talkWith(m: SuperMan) { println(s"Talk with ${m.name}") } def SayHello(msg: String)(implicit prefix: String) { println(prefix + ", " + msg) }…

Partial函数的定义 scala> val isVeryTasty: PartialFunction[String, String] = { case "Glazed Donut" | "Strawberry Donut" => "Very Tasty"}isVeryTasty: PartialFunction[String,String] = <function1> scala> isVeryTasty(&qu…

this article show you how to create a SBT project with IDEA. prerequisite: 1.JDK8 2.Scala 2.11.8 3.Intellij IDEA 2016.3 1.create a new project from: File>New>Project…

数组:可变的,可索引的,元素具有相同类型的数据集合 一维数组 scala> val intValueArr = new Array[Int](3)intValueArr: Array[Int] = Array(0, 0, 0) scala> val myStrArr = Array("BigData","hadoop","spark")myStrArr: Array[String] = Array(BigData, hadoop, s…

1 .if satement 与其它语言不同的是,scala if statement 返回的是一个值 scala> val a = if ( 6 > 0 ) 1 else -1a: Int = 1 2. while statement 3. do.. while statement 4 for statement for ( 变量 <-  表达式 ) { 语句块}: scala> for ( i <- 1 to 3 ) println(i)123 scala> for…

scala读文件:   example: scala> import scala.io.Sourceimport scala.io.Source scala> var inputFile = Source.fromFile("text.txt")inputFile: scala.io.BufferedSource = non-empty iterator scala> for ( line <- inputFile.getLines()) println(lin…

scala 写文件功能: scala> import java.io.PrintWriterimport java.io.PrintWriter scala> val outputFile = new PrintWriter("text.txt")outputFile: java.io.PrintWriter = java.io.PrintWriter@213c812a scala> outputFile.println("hello panzidong&q…

控制台输出语句: print println example: scala> print("i=");print(i)i=345scala> println("hello ");println("world")hello world…

控制台输入语句: readInt, readDouble, readByte, readShort, readLong, readChar, readBoolean, readLine example:scala> import io.StdIn._import io.StdIn._ scala> var i=readInt()2i: Int = 2 scala> var f=readFloat()2.2f: Float = 2.2 scala> var b=readBoolean…

scala 变量: val : 声明时,必须被初始化,不能再重新赋值. scala> test = "only1"<console>:11: error: not found: value test test = "only1" ^<console>:12: error: not found: value test val $ires0 = test ^    var :可被多次赋值. scala> var test2 = &qu…

scala 操作符: 算术运算符:  +  - *  / % 关系统运算符: > , < ,= ,!= ,>=,<=, 逻辑运算符: && . || , ! 位运算符:&, |, ^,~,<<,>>,>>>(无符号右移) 赋值运算符: = 优先及由上及下…

package com.example import akka.actor._ object Tutorial_02_Tell_Pattern extends App { println("Step 1: Create an actory system") val system = ActorSystem("DonutStoreActorSystem") val donutInActor = system.actorOf(Props[DonutInActor], n…

collect will apply a partial function to all elements of a Traversable and return a different collection…

The Scala collections library provides specialised implementations for Sets of fewer than 5 values (see the source). The iterators for these implementations return elements in the order in which they were added, rather than the consistent, hash-based…