scala in depth

Note: This study originates from: DT Big Data DreamWorks (public number: Dt_spark)1.in the previous section we learned about Scala Hello World, specifically defining a function as follows:650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M02/70/40/wKiom1W1CI_DmfpAAAGAJtFJ734715.jpg "title=" 1.png " alt= "Wkiom1w1ci_dmfpaaagajtfj734715.jpg"/>2.define a function without parameters, as follows:650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M

3, hands on the abstract class in ScalaThe definition of an abstract class requires the use of the abstract keyword: The above code defines and implements the abstract method, it is important to note that we put the direct running code in the trait subclass of the app, about the inside of the app helps us implement the Main method and manages the code written by the engineer;Here's a look at the use of uninitialized variables in an abstract class: 4, hands-on trait in ScalaTrait

it's so ....Come back at night suddenly saw into the huge manuscript, can't help to the three ye, and then nothing did 23 o'clock ... 85th: The powerful expressive battle of the for expression in ScalaGoal:Comparison and contact of higher order functions (FLATMAP,MAP) and for loops (initial)Gains:The back of the For loop is actually called map, but it is more likely to be programmed with a for loop if the statement is concise and expressive two.MORE:Run the instance code over and try it out.----

for (generator; definition; filter) to Do data filtering queryPackage Com.dt.scala.forexpressionCase Class Book (title:string, Authors:list[string])Object For_query {def main (args:array[string]) {Val Books:list[book] = List (Book ("Structure and Interpretation", List ("Abelson, Harold", "Sussman"),Book ("Principles of Compiler Design",List ("Aho, Alfred", "Ullman, Jeffrey")),Book ("Programming in Modula-2", List ("Wirth, Niklaus")),Book ("Introduction to Functional Programming", List ("Bird, Ri

The code jumps inside the for loop are map, withfilter, etc.For is more direct than MAP,FILTER,FLATMAP, can be implemented with a for replacementPackage Com.dt.scala.forexpressionObject For_advanced {def main (args:array[string]) {}def Map[a, b] (list:list[a], f:a = b): list[b] =for (element def Flatmap[a, B] (list:list[a], f:a = List[b]): list[b] =for (x def Filter[a] (list:list[a], f:a = Boolean): list[a] =for (Elem }DT Big Data Dream Factory public account: Dt_spark.DT Big Data Dream Factory'

Note: This study originates from: DT Big Data DreamWorks (public number: Dt_spark)1.in the previous section we learned about Scala Hello World, specifically defining a function as follows:650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M02/70/40/wKiom1W1CI_DmfpAAAGAJtFJ734715.jpg "title=" 1.png " alt= "Wkiom1w1ci_dmfpaaagajtfj734715.jpg"/>2.define a function without parameters, as follows:650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M

Some time ago Read the "Fast Learning Scala", feel that writing is not very good, so began to see this "programming Scala", the book's Code has been realized a bit, now put in the blog to share. Package BASE04 /** * Scala's class * Created by DD on 2016/5/18 0018. * /Object demo01 extends app{ class car (val year:int) { private var milesdriven:int = 0 def miles () = Miles Driven def D

1. Create a map 1) Create immutable mappings scala> val status = Map (1, "a", 2, "B") status:scala.collection.immutable.map[int,string] = map (1-A , 2-B) scala> val status = Map ((1, "a"), (2, "B")) status:scala.collection.immutable.map[int,string] = Map (1-A, 2-B) 2) Create a mutable mapping either by importing it into the scope or by specifying the full path to the Scala.collection.mutable.Map class w

The Akka provides scalable, real-time transaction processing capabilities.The Akka is based on actor and provides location transparency.The 1GB heap can have 2.5 million actors.Horizontal expansion, vertical expansion, fault tolerance 3 ways to solve.The actor of the tree structure, each actor has state and behavior.DT Big Data Dream Factory public account: Dt_spark.DT Big Data Dream Factory's public number is Dt_spark, every day will have big data actual combat video release, please continue to

= { //similar to defining a static method initialization, using C to refer to a method var c=c () c.apply () c.test () }}3. Use apply to achieve a singleton mode, let's do a test. Reference the associated object C with C and C1, respectivelyPackage Smart.iotclass Applyclass { }class a{ def Test () =println ("function test") def apply () =println ( "Hello class A");} Object b{ def apply () =println ("Hello object B");} Similar to a factory method, use the C apply method

:: Appends the object to the head of the list.The head part of an existing list[subclass X] is placed in another object A, which is a subclass Y, and if both a object and the original list object inherit from the same parent class, the list is displayed as the list[parent class].The parameters of the function are contravariant so that covariance cannot occur, so the nether is used to solve the problem. The object to which the:: Method returns is programmed as a list of upper bound object B.inter

Package Com.dt.scala.listObject Listbuffer_internals {def main (args:array[string]) {Val list = list (1,2,3,4,5,6,7,8,9)Increment (list)Increment_moreeffective (list)Increment_mosteffective (list)}def increment (List:list[int]): list[int] = list match {Case list () = List ()Case HEAD:: tail = head + 1:: Increment (tail)}def increment_moreeffective (List:list[int]): list[int] = {var result = List[int] ()for (element Result}def increment_mosteffective (List:list[int]): list[int] = {Import Scala.co

Default value:def saymyname (name:string = "Jack") {println (name)}Variable parameters:def summoreparameters (elem:int*) = { var sum = 0for (e Use of underscores:def add (a:int,b:int) = a+bdef add2 = Add (_:int,2)Recursive functions: Need to explicitly give the return type of the functiondef FAC (n:int): Int = if (n function currying:Write this argument independently, this is curryingdef mulitply (X:int) (y:int) = x*ydef m2 = mulitply (2) _;Curry is the parameter can be separated, some of the

From Scala wizard Chapter 1 functional objects With the basic Scala knowledge gained from the previous chapters, you are ready to explore how to design objects with more comprehensive features in Scala. This chapter focuses on defining functional objects, that is, classes of objects without any variable states. As an example of running, we will create several Cl

Previous Article: Scala Tutorial: interaction with Java, everything is an object This document is translated from the official Scala tutorial. to prevent misunderstanding, keep the original document for reference. Due to space limitations, there are three articles. Blog formats are not easy to adjust, interested friends can download PDF version: http://download.csdn.net/source/1742639 --- 6Condition class a

Reprinted from Http://www.tuicool.com/articles/jYzuAv and http://www.importnew.com/1537.htmlIn a keynote speech that I collaborated with Martin Fowler, he made an insightful point:The legacy of Java will be the platform, not the programming language.The original engineers of Java technology made a wise decision to separate the programming language from the runtime environment, which ultimately enabled more than 200 languages to run on the Java platform. This architecture is critical to the long-

Scala basic syntax If you have a good understanding of the Java language, it will be easy to learn Scala. The most important difference between Scala and Java is that the line terminator is optional. Consider a Scala program that can be defined as a collection of objects that communicate by calling each other's methods

this. Implicit resolution of search scopes The rules in this section are somewhat complex, as described in the Scala in Depth, where the search logic at the top is: looking under the current scope. This situation is divided into two cases, one is to display the implicit element of the declaration in the current scope, and the other to import the implicit element through the import. If the first method is n

introduced to the current scope, in which an implicit transformation from the type any to the ARROWASSOC is defined. So when using "one", 1, the compiler automatically inserts the conversion from 1 to Arrowasso c.Type classThe type class is a very flexible design pattern that separates the definition and behavior of a type, making it very convenient to extend class behavior. Or if we want to create a feature that spans types (that is, functional implementations are independent of the type), the

Java will be a platform rather than a programming language. The original engineers of Java made a wise decision to separate the programming language from the runtime environment, which eventually allowed over 200 languages to run on the Java platform. This architecture is crucial to the long-term vitality of the platform, because the computer programming language generally has a short life cycle. The annual JVM language summit, sponsored by Oracle, started in 2008, provided an opportunity for op