Модерни езици за програмира за JVM

JRuby, Groovy, Scala и Clojure.

Що е Java?

Програмен език

Виртуална машина

Стандартна библиотека

The beating heart of Java is not the Java programming language - it is the JVM and the

entire infrastructure built around it...

Maximus Decimus Meridius, Roman General & Java Programmer

Езикът Java

Създаден да замени С++

Интегрира някои добри идеи от Lisp

Характеризира се с консервативен, но практичен дизайн

Проблемите на езикът Java

Не е чист обектно-ориентиран език

Няма никаква поддръжка за функционален стил на програмиране

Не е особено експресивен

Развитието му е ограничено от изискванията за обратна съвместимост

Че то алтернативи има ли?

1996 - Java 1.0

1997 - 40 езика вече имат версия за JVM

2004 - 169 са JVM compatible

2011 - приблизително 300 езика се целят в JVM

Причината?

The JVM is rock solid and heart touching at the same time.

Отлична производителност и прекрасен optimizer

Огромна база съществуващ Java код

Купища страхотни иструменти

Не всичко е ток и жица

Java (< 7) нямаше поддръжка за динамичен метод dispatching

JVM не е оптимизиран за функционален стил на програмиране

JVM пали относително бавно

JVM имплементациите на някои езици (като Python) не са съвсем съвместими с native (C) имплементациите им

Двете страни на Силата

Езици портнати към JVM

Езици създадени специално за JVM

Претендентите

JRuby

Jython

Fantom

Groovy

Scala

Clojure

Ruby

динамичен език за програмиране

компактен и елегантен синтаксис

създаден да направи програмистите щастливи

made in Japan

Преди Ruby

Сега (като Ruby програмист)

Hello, Ruby# Output "I love Ruby"say = "I love Ruby"puts say # Output "I *LOVE* RUBY"say['love'] = "*love*"puts say.upcase # Output "I *love* Ruby"# five times5.times { puts say }

JRuby - Java & Ruby sitting in a tree

Ruby е елегантен език с бавен runtime

JVM е много бърз runtime

JRuby дава възможност на Java програмистите да използват технологии като Rails

JRuby дава възможност на Ruby програмистите да ползват Java библиотеки

jruby-1.6.1 :001 > puts "Hello, JRuby"Hello, JRuby => niljruby-1.6.1 :002 > arr = ["Chuck", "Sarah", "Morgan", "Casey"] => ["Chuck", "Sarah", "Morgan", "Casey"]jruby-1.6.1 :003 > arr.length => 4jruby-1.6.1 :004 > arr.size => 4jruby-1.6.1 :005 > arr.size() => 4jruby-1.6.1 :006 > arr.each { |name| puts name }ChuckSarahMorganCasey => ["Chuck", "Sarah", "Morgan", "Casey"]jruby-1.6.1 :007 > arr.each_with_index { |name, index| puts "##{index}: #{name}"}0: Chuck1: Sarah2: Morgan3: Casey => ["Chuck", "Sarah", "Morgan", "Casey"]

Загрявка в jirb

Ако прилича на патица...class Duck def walk puts "The duck walks" end

def quack puts "The duck quacks" endend

class Dog def walk puts "The dog walks" end

def quack puts "The dog quacks" endend

def test_animal(animal) animal.walk animal.quackend

test_animal(Duck.new)test_animal(Dog.new)

Java от Rubyrequire 'java'java_import 'java.lang.System'java_import 'java.util.ArrayList'java_import 'javax.swing.JOptionPane'

System.out.println("Feel the power of JRuby")

## using snake_names for Java method namesputs System.current_time_millis## regular names work as wellputs System.currentTimeMillis

array_list = ArrayList.new

## the array list supports some common Ruby idiomsarray_list << 1array_list.add 2array_list << 3

puts "List length is ##{array_list.length}"

array_list.each { |elem| puts elem }

## a glimpse of SwingJOptionPane.show_message_dialog(nil, "This is a message from the future of Ruby!")

Ruby от Java

import org.jruby.embed.InvokeFailedException;import org.jruby.embed.ScriptingContainer;

public class RubyFromJava { public static void main(String[] args) { ScriptingContainer container = new ScriptingContainer(); container.runScriptlet("puts 'Ruby bridge established successfully'" ); }}

Стана ми интересно, къде да науча повече?

http://batsov.com/articles/2011/05/18/jvm-langs-jruby/

It’s a Groovy kind of love...

Хвала на Groovy

Groovy is like a super version of Java. It can leverage Java's enterprise capabilities but also has

cool productivity features like closures, builders and dynamic typing. If you are a developer, tester

or script guru, you have to love Groovy.

def name='World'; println "Hello $name!"

class Greet { def name Greet(who) { name = who[0].toUpperCase() + who[1..-1] } def salute() { println "Hello $name!" }}

g = new Greet('world') // create objectg.salute() // output "Hello World!"

import static org.apache.commons.lang.WordUtils.*

class Greeter extends Greet { Greeter(who) { name = capitalize(who) }}

new Greeter('world').salute()

groovy -e "println 'Hello ' + args[0]" World

Groovy e...

динамичен

изцяло обектно-ориентиран

вдъхновен от Ruby, Python и Smalltalk

със синтаксис много близък до този на Java

създаден да улесни живота на Java програмистите

Ключовите моменти

closures

attributes

duck typing

аритметика базирана на BigDecimal

улеснена работа с XML, SQL, Swing, etc

Groovy & Java

Groovy програмите се компилират до Java bytecode

Същите низове, същите регулярни изрази и т.н.

Същите API

Същия модел за сигурност, същия нишков модел

Същите ОО концепции

// old school Java code, but also valid Groovy codeSystem.out.println("Hello, world!");

// idiomatic Groovyprintln "Hello, world!"

// dynamic variable definitiondef name = "Bozhidar"

// GString featuring string interpolationprintln "Hello, $name" // => "Hello, Bozhidar"

// statically typed variableString songName = "Coding in the Name of"

println "Now playing - $songName"

String multiline = """this is a multilinestring. There is not need to embednewline characters in it"""

println multiline

// method definitiondef greet(name) { println "Hello, $name!"}

// method invocationgreet "Bozhidar"greet("Bozhidar")

showSize([1, 2, 3])// this is the important partshowSize(null)

// a listdef beers = ["Zagorka", "Bolyarka", "Shumensko", "Ariana"]

// list accessprintln "My favourite beer is ${beers[1]}"

beers.each { beer -> println beer }

// imports can appear anywhere and support the creation of aliasesimport static java.util.Calendar.getInstance as nowimport java.sql.Date as SDate

println now()// java.util package is automatically imported in Groovy so this is java.util.Dateprintln new Date()println new SDate(2011, 5, 5)

// language support for regular expressionsif ("Hello, Groovy" =~ /\w+,\s\w+/) { println "It matches"}

// range filtering with higher-order functions(1..10).findAll { n -> n % 2 == 0}.each { n -> println n }

// mapdef capitols = [Bulgaria: "Sofia", USA: "Washington", England:"London", France:"Paris"]

println capitols["Bulgaria"] // => Sofiaprintln capitols["France"] // => Paris

// class definitionclass Person { def name def age

Person(name, age) { this.name = name this.age = age }

@Override String toString() { return "Name {$name}, age {$age}" }}

def me = new Person("Bozhidar", 26)println me

JDBC подобренияimport groovy.sql.Sqlsql = Sql.newInstance("jdbc:mysql://host/db", "username", "password", "com.mysql.jdbc.Driver")sql.eachRow("select * from tableName", { println it.id + " -- ${it.firstName} --"} )

1 -- Bozhidar --2 -- Jim --3 -- Jack --4 -- Valentine --

Изход от програмата

XML<books> <book> <title>Dune</title> <author firstname="Frank" lastname="Herbert"/> </book> <book> <title>Dune Messiah</title> <author firstname="Frank" lastname="Herbert"/> </book> <book> <title>Children of Dune</title> <author firstname="Frank" lastname="Herbert"/> </book> <book> <title>A Game of Thrones</title> <author firstname="George" lastname="Martin"/> </book></books>

def books = new XmlSlurper().parse("books.xml")books.book.each { println "Title = ${it.title}, Author: ${it.author.@firstname} ${it.author.@lastname}"}

Builders

import groovy.xml.*

def page = new MarkupBuilder()page.html { head { title 'Hello, Groovy!' } body { div { 3.times { p "Groovy power!" } } }}

<html> <head> <title>Hello, Groovy!</title> </head> <body> <div> <p>Groovy power!</p> <p>Groovy power!</p> <p>Groovy power!</p> </div> </body></html>

Swingimport java.awt.FlowLayout

builder = new groovy.swing.SwingBuilder()langs = ["Groovy", "Scala", "Clojure"]gui = builder.frame(size: [290, 100], title: 'Groovy Swing') { panel(layout: new FlowLayout()) { panel(layout: new FlowLayout()) { for (lang in langs) { radioButton(text: lang) } } button(text: 'Perform Magic', actionPerformed: { builder.optionPane(message: "Feel the power of Groovy!"). createDialog(null, 'Message').show() }) button(text: 'Quit', actionPerformed: {System.exit(0)}) }}gui.show()

Инструментите на занаята

groovy - интерпретатор

groovysh - конзола

groovyc - компилатор

groovyconsole - графична конзола

Приложения убийци (killer apps)

Grails - модерна платформа за разработка на уеб приложения, вдъхновена от Ruby on Rails

Gradle - могъщ build tool, създаден да наследи Maven

Griffon - модерна платформа за разработка на Swing приложения

IDE-та, нещо?

IntelliJ IDEA - Bozhidar’s Choice

Eclipse

NetBeans

Where do we go now?

http://batsov.com/articles/2011/05/06/jvm-langs-groovy/

Ride the eSCALAtor

If I were to pick a language to use today other than Java, it would be Scala...

James Gosling, father of Java

Отмъщението на статично типизираните езици

Scala е статично типизиран език (като Java)

Scala използва type inference механизъм, който сериозно намалява типовите декларации

Кодът написан на Scala е толкова сигурен и бърз, колкото този написан на Java

ООП и ФП могат да съжителстват в мир и любов

Scala е чисто обектно-ориентиран език

Scala включва в себе си много елементи от функционалното програмиране

higher order functions

function objects

pattern matching

tail recursion

Expressive

scala> val romanToArabic = Map("I" -> 1, "II" -> 2, "III" -> 3, "IV" -> 4, "V" -> 5)romanToArabic: scala.collection.immutable.Map[java.lang.String,Int] = Map((II,2), (IV,4), (I,1), (V,5), (III,3))

scala> romanToArabic("I")res2: Int = 1

scala> romanToArabic("II")res3: Int = 2

Компактен код, без излишна церемония

public boolean hasUpperCase(String word) { if (word == null) { return false; } int len = word.length(); for (int i = 0; i < len; i++) { if (Character.isUpperCase(word.charAt(i))) { return true; } } return false;}

def hasUppercase(word: String) = if (word != null) word.exists(_.isUpperCase) else false

Java

Scala

Оптимизиран за мързели

class Person { private String name; private int age;

Person(String name, int age) { this.name = name; this.age = age; }

public String getName() { return name; }

public void setName(String name) { this.name = name; }

public int getAge() { return age; }

public void setAge(int age) { this.age = age; }}

class Person(var name: String, var age: Int)

Scala

Java

Актьорско майсторствоimport scala.actors.Actor._

case class Add(x: Int, y: Int)case class Sub(x: Int, y: Int)

val mathService = actor { loop { receive { case Add(x, y) => reply(x + y) case Sub(x, y) => reply(x - y) } }}

mathService !? Add(1, 3) // returns 4mathService !? Sub(5, 2) // returns 3

Патоците на власт!class Duck { def quack = println("The duck quacks") def walk = println("The duck walks")}

class Dog { def quack = println("The dog quacks (barks)") def walk = println("The dog walks")}

def testDuckTyping(animal: { def quack; def walk }) = { animal.quack animal.walk}

scala> testDuckTyping(new Duck)The duck quacksThe duck walks

scala> testDuckTyping(new Dog)The dog quacks (barks)The dog walks

Pimp my library

scala> implicit def intarray2sum(x: Array[Int]) = x.reduceLeft(_ + _)intarray2sum: (x: Array[Int])Int

scala> val x = Array(1, 2, 3)x: Array[Int] = Array(1, 2, 3)

scala> val y = Array(4, 5, 6)y: Array[Int] = Array(4, 5, 6)

scala> val z = x + yz: Int = 21

Малко повече екшънscala> println("Hello, Scala")Hello, Scala

scala> val name = "Bozhidar"name: java.lang.String = Bozhidar

scala> Predef.println("My name is "+name)My name is Bozhidar

scala> var someNumber: Int = 5someNumber: Int = 5

scala> var names = Array("Superman", "Batman", "The Flash", "Bozhidar")names: Array[java.lang.String] = Array(Superman, Batman, The Flash, Bozhidar)

scala> names.filter(name => name.startsWith("B"))res6: Array[java.lang.String] = Array(Batman, Bozhidar)

scala> names.lengthres7: Int = 4

scala> name.length()res8: Int = 8

...scala> import java.util.Dateimport java.util.Date

scala> var currentDate = new DatecurrentDate: java.util.Date = Wed May 11 15:03:20 EEST 2011

scala> println("Now is " + currentDate)Now is Wed May 11 15:03:20 EEST 2011

scala> currentDate.toStringres10: java.lang.String = Wed May 11 15:03:20 EEST 2011

scala> currentDate.toString()res11: java.lang.String = Wed May 11 15:03:20 EEST 2011

scala> currentDate toStringres12: java.lang.String = Wed May 11 15:03:20 EEST 2011

Closures

scala> var x = 10x: Int = 10

scala> val addToX = (y: Int) => x + yaddToX: (Int) => Int = <function1>

scala> addToX(2)res0: Int = 12

scala> addToX(6)res1: Int = 16

scala> x = 5x: Int = 5

scala> addToX(10)res2: Int = 15

Свързани списъциscala> 1 :: 2 :: 3 :: 4 :: 5 :: Nilres3: List[Int] = List(1, 2, 3, 4, 5)

scala> val names = List("Neo", "Trinity", "Morpheus", "Tank", "Dozer")names: List[java.lang.String] = List(Neo, Trinity, Morpheus, Tank, Dozer)

scala> names.lengthres4: Int = 5

scala> names.foreach(println)NeoTrinityMorpheusTankDozer

scala> names.map(_.toUpperCase)res6: List[java.lang.String] = List(NEO, TRINITY, MORPHEUS, TANK, DOZER)

scala> names.forall(_.length > 5)res7: Boolean = false

scala> names.forall(_.length > 2)res8: Boolean = true

...scala> names.filter(_.startsWith("T"))res9: List[java.lang.String] = List(Trinity, Tank)

scala> names.exists(_.length == 3)res10: Boolean = true

scala> names.drop(2)res11: List[java.lang.String] = List(Morpheus, Tank, Dozer)

scala> names.reverseres12: List[java.lang.String] = List(Dozer, Tank, Morpheus, Trinity, Neo)

scala> names.sortBy(_.length)res13: List[java.lang.String] = List(Neo, Tank, Dozer, Trinity, Morpheus)

scala> names.sort(_ > _)res14: List[java.lang.String] = List(Trinity, Tank, Neo, Morpheus, Dozer)

scala> names.slice(2, 4)res16: List[java.lang.String] = List(Morpheus, Tank)

scala> def testMatching(something: Any) = something match { | case 1 => "one" | case "two" => 2 | case x: Int => "an integer number" | case x: String => "some string" | case <xmltag>{content}</xmltag> => content | case head :: tail => head | case _ => "something else entirely" | }testMatching: (something: Any)Any

scala> testMatching(1)res18: Any = one

scala> testMatching("two")res19: Any = 2

scala> testMatching(2)res20: Any = an integer number

scala> testMatching("matrix")res21: Any = some string

scala> testMatching(<xmltag>this is in the tag</xmltag>)res22: Any = this is in the tag

scala> testMatching(List(1, 2, 3))res23: Any = 1

scala> testMatching(3.9)res24: Any = something else entirely

Pattern matching

def length(list: List[Any]): Int = list match { case head :: tail => 1 + length(tail) case Nil => 0}

def length(list: List[Any]): Int = { def lengthrec(list: List[Any], result: Int): Int = list match { case head :: tail => lengthrec(tail, result + 1) case Nil => result }

lengthrec(list, 0)}

Tail recursion

Plain recursion

Инвентара

scala - конзола/интерпретатор

scalac - компилатор

fsc - fast scala compiler

IDE-тата

IntelliJ IDEA - Bozhidar’s Choice

Eclipse - Official Scala IDE

NetBeans - на тоя етап е бран бостан

Убийците

Play! Framework

Lift

SBT (Simple Build Tool)

Akka

The full disclosure on Clojure

“Clojure feels like a general-purpose language beamed back from the near future. Its support for functional programming and software trans-actional memory is well beyond current practice and is well suited for multicore hardware. At the same time, Clojure is well grounded in the past and the present. It brings together Lisp and the Java Virtual Machine. Lisp brings wisdom spanning most of the history of programming, and Java brings the robustness, extensive libraries, and tooling of the dominant platform available today.”

What happens when an unstoppable force meets an

immutable object?

Clojure is dynamic

Clojure is functional

Clojure is a Lisp(1)

Clojure is designed for concurrency

Clojure is fighting accidental complexity

Стилpublic boolean hasUpperCase(String word) { if (word == null) { return false; } int len = word.length(); for (int i = 0; i < len; i++) { if (Character.isUpperCase(word.charAt(i))) { return true; } } return false;}

(defn has-uppercase? [string] (some #(Character/isUpperCase %) string))

Компактностclass Person { private String name; private int age;

Person(String name, int age) { this.name = name; this.age = age; }

public String getName() { return name; }

public void setName(String name) { this.name = name; }

public int getAge() { return age; }

public void setAge(int age) { this.age = age; }}

(defrecord person [name age])

Силата е на ваша страна

(defmacro and "Evaluates exprs one at a time, from left to right. If a form returns logical false (nil or false), and returns that value and doesn't evaluate any of the other expressions, otherwise it returns the value of the last expr. (and) returns true." {:added "1.0"} ([] true) ([x] x) ([x & next] `(let [and# ~x] (if and# (and ~@next) and#))))

;;; Lists;; list creationuser> (list 1 2 3)(1 2 3);; quoted list creationuser> (def a-list '(1 2 3 4 5 6 7 8 9 10))#'user/a-list;; find the size of a listuser> (count a-list)10user> (first a-list)1user> (rest a-list)(2 3 4 5 6 7 8 9 10)user> (last a-list)10;; find the elements of the list matching a predicate(boolean function)user> (filter even? a-list)(2 4 6 8 10)user> (filter odd? a-list)(1 3 5 7 9);; map an anonymous(lambda) function to all elements of the listuser> (map #(* % 2) a-list)(2 4 6 8 10 12 14 16 18 20);; add an element to the beginning of the listuser> (cons 0 a-list)(0 1 2 3 4 5 6 7 8 9 10);; cons in a list specific function, conj is a general purpose one and;; works on all collection (but in a different manner)user> (conj a-list 0)(0 1 2 3 4 5 6 7 8 9 10)

Сърцето на Clojure

;; retrieve the first five items in a listuser> (take 5 a-list)(1 2 3 4 5);; retrieve all but the first five items in a listuser> (drop 5 a-list)(6 7 8 9 10)user> (take-while #(< % 3) a-list)(1 2)user> (drop-while #(> % 3) a-list)(1 2 3 4 5 6 7 8 9 10)user> (drop-while #(< % 3) a-list)(3 4 5 6 7 8 9 10)

;;; Sets

user> (set '(1 2 3 4 5 1 2 3 4))#{1 2 3 4 5}user> (def a-set #{1 2 3 4 5})#'user/a-setuser> (contains? a-set 3)trueuser> (contains? a-set 7)falseuser> (conj a-set 5)#{1 2 3 4 5}user> (conj a-set 6)#{1 2 3 4 5 6}user> (disj a-set 1)#{2 3 4 5}user> (get a-set 1)1user> (get a-set 7)nil

...

;;; Mapsuser> (hash-map :Bozhidar :Batsov :Bruce :Wayne :Selina :Kyle){:Selina :Kyle, :Bozhidar :Batsov, :Bruce :Wayne}user> (def a-map {:Bozhidar :Batsov, :Bruce :Wayne, :Selina :Kyle})#'user/a-mapuser> a-map{:Bozhidar :Batsov, :Bruce :Wayne, :Selina :Kyle}user> (get a-map :Bozhidar):Batsovuser> (contains? a-map :Bozhidar)trueuser> (contains? a-map :Clark)falseuser> (:Bozhidar a-map):Batsovuser> (assoc a-map :Lois :Lane){:Lois :Lane, :Bozhidar :Batsov, :Bruce :Wayne, :Selina :Kyle}user> (keys a-map)(:Bozhidar :Bruce :Selina)user> (vals a-map)(:Batsov :Wayne :Kyle)user> (dissoc a-map :Bruce){:Bozhidar :Batsov, :Selina :Kyle}user> (merge a-map {:Alia :Atreides, :Arya :Stark}){:Arya :Stark, :Alia :Atreides, :Bozhidar :Batsov, :Bruce :Wayne, :Selina :Kyle}

Хешове

;;; Vectors

user> (vector 1 2 3 4)[1 2 3 4]user> [1 2 3 4][1 2 3 4]user> (def a-vector [1 2 3 4 5])#'user/a-vectoruser> (count a-vector)5user> (conj a-vector 13)[1 2 3 4 5 13];; random access is a constant time operation in vectorsuser> (nth a-vector 3)4user> (pop a-vector)[1 2 3 4]user> (peek a-vector)5

Вектори

(def picked-numbers (ref #{})

(def secret-num (.nextInt (java.util.Random.) 10))

(defn guess-number [n] (print "Enter a guess between 1 and 10: ") (flush) (let [guess (java.lang.Integer/parseInt (read-line)) ] (cond (= guess n) (println "You guessed correctly") (contains? (deref picked-numbers) n) (println "Pick another number! You already tried that one.") :else (dosync (alter picked-numbers conj guess)))))

user=> (guess-number secret-num)Enter a guess between 1 and 10: 1#{1}user=> (guess-number secret-num)Enter a guess between 1 and 10: 3#{1 3}user=> (guess-number secret-num)Enter a guess between 1 and 10: 5#{1 3 5}

Програмиране с refs

(def picked-numbers (atom #{})

(def secret-num (.nextInt (java.util.Random.) 10))

(defn guess-number [n] (print "Enter a guess between 1 and 10: ") (flush) (let [guess (java.lang.Integer/parseInt (read-line)) ] (cond (= guess n) (println "You guessed correctly") (contains? (deref picked-numbers) n) (println "Pick another number! You already tried that one.") :else (swap! picked-numbers conj guess))))

user=> (guess-number secret-num)Enter a guess between 1 and 10: 1#{1}user=> (guess-number secret-num)Enter a guess between 1 and 10: 3#{1 3}user=> (guess-number secret-num)Enter a guess between 1 and 10: 5#{1 3 5}

Атоми

ООП по Лиспаджийски

(defmulti my-add (fn [x y] (and (string? x) (string? y))))

(defmethod my-add true [x y] (str x y))

(defmethod my-add false [x y] (+ x y))

user=> (my-add 3 4) ; => 7user=> (my-add "3" "4") ; => "34"

Екстремист съм, какво ми трябва?

Обичайните заподозрени

Eclipse

IntelliJ

NetBeans

Emacs + SLIME = Bozhidar’s Choice

Повече инфо, моля!

http://batsov.com/articles/2011/05/12/jvm-langs-clojure/

Stay hungry, stay foolish!

FIN