the adventurous developers guide to jvm languages

THE ADVENTUROUS DEVELOPERS GUIDE TO JVM LANGUAGES

SIMON MAPLE @SJMAPLE

Monday, 30 September 13

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Heard of the Language Used the languageJava Scala Groovy Clojure Ceylon Kotlin Xtend


JAVA

“Most people talk about Java the language, and this may sound odd coming from me, but I could hardly care less. At the core of the Java ecosystem is the JVM.”

James Gosling,creator of the Java programming language (2011, TheServerSide)


JAVA THE JVM

“Most people talk about Java the language, and this may sound odd coming from me, but I could hardly care less. At the core of the Java ecosystem is the JVM.”

James Gosling,creator of the Java programming language (2011, TheServerSide)


LANGUAGES BUILT FOR THE JVM


LANGUAGES PORTED TO THE JVM


R.I.P ?


JAVA 8

1. DON’T BREAK BINARY COMPATIBILITY

2. AVOID INTRODUCING SOURCE INCOMPATIBILITIES

3. MANAGE BEHAVIORAL COMPATIBILITY CHANGES


LET’S EXPERIMENT


COMPANION CLASS

THERE IS NO STATIC

import HttpServer._ // import statics from companion object


VARIABLES

THERE IS NO FINAL

val name: Type = initializer // immutable value

var name: Type = initializer // mutable variable


CASE CLASScase class Status(code: Int, text: String)

case method @ ("GET" | "HEAD") => ... case method => respondWithHtml( Status(501, "Not Implemented"), title = "501 Not Implemented", ) body = <H2>501 Not Implemented: { method } method</H2> ...


STRINGS

val header = s""" |HTTP/1.1 ${status.code} ${status.text} |Server: Scala HTTP Server 1.0 |Date: ${new Date()} |Content-type: ${contentType} |Content-length: ${content.length} """.trim.stripMargin + LineSep + LineSep


NULL

def toFile(file: File, isRetry: Boolean = false): Option[File] = if (file.isDirectory && !isRetry) toFile(new File(file, DefaultFile), true)

else if (file.isFile)Some(file)

else None


COMPLEXITY


JAVA SUPERCHARGED!


NULL

def streetName = user?.address?.street


ELVIS LIVES

def displayName = user.name ?: "Anonymous"


CLOSURES

square = { it * it }

[ 1, 2, 3, 4 ].collect(square) // [1, 4, 9, 16]


COLLECTIONS

def names = ["Ted", "Fred", "Jed", "Ned"]

5p[5 println names //[Ted, Fred, Jed, Ned]

def shortNames = names.findAll { it.size() <= 3 }

shortNames.each { println it } // Ted // Jed // Ned


GROOVY 2.0 - DYNATIC

void someMethod() {}

void test() {

sommeeMethod()}




void test() {

sommeeMethod()}

import groovy.transform.TypeChecked

@TypeChecked




void test() {

sommeeMethod()}

// compilation error: // cannot find matching method sommeeMethod()

import groovy.transform.TypeChecked

@TypeChecked


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YEH, WE SAVE LIVES


REPL

<Python user> Can you believe these JVM geeks think this is impressive?<Perl user> Tell me about it! Welcome to the 90s<Python user> Yeh, “Hey the 20th century called to say they wanted their code back”!<Groovy user> Hey, we do this too!


FUNCTIONAL PRINCIPLES1. LITTLE OR NO SIDE EFFECTS

2. FUNCTIONS SHOULD ALWAYS RETURN THE SAME RESULT IF CALLED WITH THE SAME PARAMETERS

3. NO GLOBAL VARIABLES

4. FUNCTIONS AS FIRST ORDER CITIZENS

5. LAZY EVALUATION OF EXPRESSIONS


WHOA!

(defn send-html-response "Html response" [client-socket status title body] (let [html (str "<HTML><HEAD><TITLE>" title "</TITLE></HEAD><BODY>" body "</BODY></HTML>")] send-http-response client-socket status "text/html" (.getBytes html "UTF-8")) ))


LET’S GET FUNCTIONAL

(defn process-request "Parse the HTTP request and decide what to do" [client-socket] (let [reader (get-reader client-socket) first-line (.readLine reader) tokens (clojure.string/split first-line #"\s+")] (let [http-method (clojure.string/upper-case (get tokens 0 "unknown"))] (if (or (= http-method "GET") (= http-method "HEAD")) (let [file-requested-name (get tokens 1 "not-existing") [...]


INTEROP

(ns clojure-http-server.core (:require [clojure.string]) (:import (java.net ServerSocket SocketException) (java.util Date) (java.io PrintWriter BufferedReader InputStreamReader BufferedOutputStream)))


LET’S EXPERIMENT


SUMMARY

FUNCTIONS ARE FIRST CLASS CITIZENS

AND SHOULD BE TREATED AS SUCH!


SUMMARY

STATICALLY TYPED LANGUAGES ROCK


SUMMARY

EVERYONE’S SYNTAX SUCKS...


SUMMARY

EVERYONE’S SYNTAX SUCKS...

TO SOMEONE ELSE.


SUMMARY

THE JVM IS AWESOME


BE ADVENTUROUS!


YOU, ONE HOUR LATER

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Java Scala Groovy Clojure Ceylon Kotlin Xtend


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TECH REPORTS WRITTEN BY OUR DEVELOPERS



JAVA 8, CONTINUOUS DELIVERY,

APP SERVER DEBATE, JVM WEB FRAMEWORKS,

PRODUCTIVITY REPORTS...



AND...

THE ADVENTUROUS DEVELOPERS GUIDE TO JVM LANGUAGES


RESOURCES

HTTPSERVER EXAMPLES OF EACH LANGUAGE ON GITHUBhttps://github.com/zeroturnaround/jvm-languages-report

THE ADVENTUROUS DEVELOPERS GUIDE TO JVM LANGUAGEShttp://zeroturnaround.com/rebellabs/devs/the-adventurous-developers-guide-to-jvm-languages/


https://github.com/zeroturnaround/jvm-languages-report

https://github.com/zeroturnaround/jvm-languages-report

http://zeroturnaround.com/rebellabs/devs/the-adventurous-developers-guide-to-jvm-languages/




RESOURCES

SIMON MAPLE@SJMAPLE


the adventurous developers guide to jvm languages

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