scala in depth

Answer the previous article.1. Is there also a syntax for declaring upper bound and Lower Boud in Java? Some, such as:ListWhat is the difference between listListListPackage Tstge;import java.util.*;p ublic class Tst {public static void main (string[] args) {arraylistThe type of 3.Java can usually be translated directly into the Scala type. But like IteratorIterator[t] Forsome {type T} or Iterator[_]Iterator[t] Forsome {type T About Forsome,stack overf

] (M:either[a, B]) ( F:b = Either[a, c]): Either[a, C]}4. For a high-order type a[t], the compatibility of a[t] varies with the specific type of T in three casesSuppose s(1) Invariant (2) covariant (3) contravariant Original:AHigher-kinded type that's invariant implies that for any typesT,A, andBIfT[a]c Onforms to T[B " Span style= "font-family: ' Newbaskerville-roman '; Font-size:10pt;color:rgb (0,0,0); Font-style:normal;font-variant: normal; " >then must be the equivalent type of b T[a] Confo

High-order function filter Source analysisPackage Com.dt.scala.forexpressionCase class Person (name:string, Ismale:boolean, children:person*)Object For_expressive {def main (args:array[string]) {Val Lauren = person ("Lauren", false)Val Rocky = person ("Rocky", True)Val Vivian = person ("Vivian", False, Lauren, Rocky)Val persons = List (Lauren, Rocky, Vivian)Val result = Persons filter (person =!person.ismale) FlatMap (person =(Person.children map (child = (Person.name, child.name)))println (Resu

is defined as follows:The Foo method defines the constraint a:b, which means that the type of parameter x is a, and that the Foo method must have an available implicit value b[a] present, and the context definition can be re-written:This Foo method defines two parameters whose implicit arguments accept a value of type b[a]. Although the second form would be more words, he gave the implicit value a user-defined label.Instance Program 1:Instance Program 2: 8. Introduction to the u

Summary:By implicit conversion, programmers can deliberately omit some information when writing Scala programs, allowing the compiler to attempt to derive this information automatically during compilation, which can greatly reduce the amount of code, ignoring lengthy, overly detailed code.How to use:1. Mark the method or variable as implicit2. Marks the parameter list of the method as Implicit3. Mark the class as implicit

We're going to learn the next dependency injection. Let's start with the code:Package Scala.learnTrait Logger {def log (msg:string)}Trait Auth {Auth:logger =Def Act (msg:string) {Log (msg)}}Object DI extends Auth with Logger {Override def log (msg:string) = println (msg)}Object test57{def main (args:array[string]) {Di.act ("I hope you'll like it")}}First, define a trait, which is the structure type.Then define another trait, its this pointer alias is auth, and specify mixed logger traits. In thi

Today, a friend of mine asked me questions about the app trait call, and I went to spend some time grooming it.Let's look at the app source first. What is app trait Trait App refers to Scala.app, our single object can be run with this trait, without having to define the main method, see the code Object Test1 { def main (args:array[string]) { println ("Run" }} object Test2 extends app{ println ("also run") } The results of the operation will naturally

spec mode. One of my blogs, "Scalatest's Test style," details the respective syntax.A widely used test tool is Gatling, which is a performance testing and stress testing tool developed based on Scala, Akka, and Netty. Liu, a colleague of mine, wrote a detailed in-depth introduction to Gatling in the article "New Generation server performance testing Tool Gatling" published in Infoq.Scalameter is also a ver

This course focuses onSpark, the hottest, most popular and promising technology in the big Data world today. In this course, from shallow to deep, based on a large number of case studies, in-depth analysis and explanation of Spark, and will contain completely from the enterprise real complex business needs to extract the actual case. The course will cover Scala programming, spark core programming, spark SQL

First, Scala overviewcan expand? Object Oriented? function-type programming compatible with Java Interop Syntax concise ? code line short ? ? abstract control statically typed can examine secure refactoring support concurrency control Customize other control structures Ii. installation of ScalaIdeEclipse (native support, use more complex)IntelliJ (expensive)NetBeans

Tags: nbsp idea Big Data development GTK Target 1.3 website startup technology sharingStep Two: Install IntelliJ idea　If 3 nodes such as Master, Slave1, Slave2, it is recommended to install it on the master nodeTo Https://www.jetbrains.com/idea download the corresponding version of the file,Because, I usually install the JDK myself, without the openjdk of CentOS, so I download the version as followsThen unzip it.The following is the directory where IntelliJ idea was installedThen proceed to the

Scala Development Environment BuildingLet's start with some of the reasons why I study Scala: The JVM's dominance in the enterprise, Scala is also the language on the JVM, and it is likely that the future will be too much from Java to Scala. Advanced functional programming and object-oriented integration.

Scala tutorial, scala Programming The following is a complete scala getting started tutorial I have collected from the Internet. I have followed other programming basics to get started. Compared with other languages such as Java, Scala is a complex language. It is a unity of object-oriented and function-oriented. It is

, I thought I knew how Scala works. Maybe they sometimes need braces. You might think you're using a function, but you're actually using a method. In practice, you can do great things with Scala, even if you don't understand the difference between methods and functions. If you're a beginner in Scala and you're reading the difference between the two, you might not

Scala supports scripts 1) create a file hello. Scala under/opt/Scala-script and edit the file as follows: $ Hello, this is the first Scala script 2) run the script 　　　　 The command line parameters of the scala script are saved in the sc