Alternate JVM Languages

Abhijeet Lele Vladimir Zakharov

21/04/2011

Goldman Sachs

GoalsGoals

Our Guarantee:You won’t become knowledgeable,

but you will become aware

JavaJava

Interview With Josh BlochInterview With Josh Bloch

Can you give us an example of code that you are most proud of creating and explain why?

The Collections framework. It's far from perfect, but it's proven itself maintainable and pleasant over the years. Doug Lea built many parts of java.util.concurrent atop it. And I still get letters from programmers telling me how much more pleasant it makes their jobs. It lets you write stuff like this little program, which computes all the anagrams in the file on standard input.

From “2008 JavaOne Conference - Rock Star Joshua Bloch”http://java.sun.com/javaone/sf/2008/articles/rockstar_joshuabloch.jsp

Anagram Algorithm: How It WorksAnagram Algorithm: How It Works

Java ExampleJava Exampleimport java.util.*;public class Anagram { public static void main(String[] args){ int minGroupSize = Integer.parseInt(args[0]);// Read words from input and put into simulated multimap

Map<String, List<String>> anagrams = new HashMap<String, List<String>>(); for (Scanner s = new Scanner(System.in); s.hasNext();) {String word = s.next();String alphagram = alphagram(word);List<String> group = anagrams.get(alphagram);if (group == null)anagrams.put(alphagram, group = new ArrayList<String>());

group.add(word);}// Print all permutation groups above size threshold

for (List<String> group : anagrams.values())if (group.size() >= minGroupSize)System.out.println(group.size() + ": " + group);

}private static String alphagram(String s){ char[] chars = s.toCharArray();Arrays.sort(chars);return String.valueOf(chars);

From “2008 JavaOne Conference - Rock Star Joshua Bloch”

http://java.sun.com/javaone/sf/2008/articles/rockstar_joshuabloch.jsp

Java Example With Deluxe FeaturesJava Example With Deluxe Featuresimport java.util.*;public class Anagram {public static void main(String[] args) {int minGroupSize = Integer.parseInt(args[0]);Map<String, List<String>> anagrams = new HashMap<String, List<String>>(); for (Scanner s = new Scanner(System.in); s.hasNext();) {String word = s.next();String alphagram = alphagram(word);List<String> group = anagrams.get(alphagram);if (group == null)anagrams.put(alphagram, group = new ArrayList<String>());

group.add(word); }List<List<String>> winners = new ArrayList<List<String>>();for (List<String> group : anagrams.values())if (group.size() >= minGroupSize)winners.add(group);

Collections.sort(winners, new Comparator<List<String>>() {public int compare(List<String> o1, List<String> o2) {return o2.size()-o1.size();

}});for (List<String> winner: winners)System.out.println(winner.size() + ": " + winner);

private static String alphagram(String s) {char[] chars = s.toCharArray();Arrays.sort(chars);return String.valueOf(chars);

Additional code from “The Java™ Tutorial > Collections”

http://download.oracle.com/javase/tutorial/collections/algorithms/index.html

Multimap

Filter

Alphagram

GroovyGroovy

What is Groovy?What is Groovy?

• Definition– A lightweight, low-ceremony, dynamic, object-oriented language– Open sourced under Apache License, version 2.0– “marvelous, wonderful, excellent, hip, trendy.” (Merriam-

Webster)

• Like Java– Follows Java semantics– Seamlessly integrates with Java– Compiles into Java bytecode – Extends the Java API and libraries – Groovy scripts can be injected into Java

• Not like Java– Dynamic Language– Closures– Properties– Native syntax for lists, maps, and regular expressions

String.metaClass.alphagram = {

char[] chars = delegate.toCharArray()

Arrays.sort(chars)

return String.valueOf(chars)

private static String alphagram(String s) {

char[] chars = s.toCharArray();

Arrays.sort(chars);

return String.valueOf(chars);

Groovy: AlphagramGroovy: Alphagram

JavaJava

GroovyGroovy

String.metaClass.alphagram = { return delegate.toList().sort().join()

Groovy Groovy -- erer

anagrams = (new Scanner(System.in)).toList().groupBy {it.alphagram()}

Map<String, List<String>> anagrams = new HashMap<String, List<String>>();

for (Scanner s = new Scanner(System.in); s.hasNext();) {

String word = s.next();

String alphagram = alphagram(word);

List<String> group = anagrams.get(alphagram);

if (group == null)

anagrams.put(alphagram, group = new ArrayList<String>());

group.add(word);

Groovy: Building MultimapGroovy: Building Multimap

JavaJava

GroovyGroovy

winners = anagrams.values().findAll { it.size > minWordCount }

winners = winners.sort { -it.size }

winners.each { println "${it.size} : $it" }

List<List<String>> winners = new ArrayList<List<String>>();

for (List<String> group : anagrams.values())

if (group.size() >= minGroupSize)

winners.add(group);

Collections.sort(winners, new Comparator<List<String>>() {

public int compare(List<String> o1, List<String> o2) {

return o2.size()-o1.size();

for (List<String> winner: winners)

System.out.println(winner.size() + ": " + winner);

Groovy: Filtering, Sorting, PrintingGroovy: Filtering, Sorting, Printing

JavaJava

GroovyGroovy

Groovy: Putting It All TogetherGroovy: Putting It All Together

minWordCount = args[0].toInteger();

(new Scanner(System.in)).toList()

.groupBy { it.alphagram() }

.values()

.findAll { it.size > minWordCount }

.sort { -it.size }

.each { println "${it.size} : $it" }

Java ReminderJava Reminderimport java.util.*;public class Anagram {public static void main(String[] args) {int minGroupSize = Integer.parseInt(args[0]);Map<String, List<String>> anagrams = new HashMap<String, List<String>>(); for (Scanner s = new Scanner(System.in); s.hasNext();) {String word = s.next();String alphagram = alphagram(word);List<String> group = anagrams.get(alphagram);if (group == null)anagrams.put(alphagram, group = new ArrayList<String>());

(new Scanner(System.in)).toList().groupBy { it.alphagram() } .values().findAll { it.size > minWordCount }.sort { -it.size }.each { println "${it.size} : $it" }

ScalaScala

What is Scala?What is Scala?

• Like Java– Bytecode looks very similar to javac output– Familiar object-oriented concepts– Static types, only better (better type inference, better generics,

implicit parameters)– Performance equivalent to Java– Java code can depend on Scala code

• Not like Java– Functional principles– Closures– Everything is an object– No such thing as static – Greatly improved type inference and generics– Traits (mixins)– Pattern Matching

word => word.sorted

Arrays.sort(chars);

Scala: AlphagramScala: Alphagram

_.sorted

JavaJava

ScalaScala

Scala With UnderbarScala With Underbar

val map = new BufferedReader(new InputStreamReader(System.in)).readLine().split(" ").groupBy( _.sorted)

if (group == null)

group.add(word);

Scala: Building MultimapScala: Building Multimap

JavaJava

ScalaScala

val winners = map.values.filter(_.size > Integer.parseInt(args(0))).toListval sorted = winners.sortBy(-_.size)

winners.add(group);

Scala: Filtering And SortingScala: Filtering And Sorting

JavaJava

ScalaScala

for (winner <- sorted.view)

println(winner.size + ": " + winner)

Scala: PrintingScala: Printing

sorted.view.map(list => list.size + ": " + list).foreach(println)

JavaJava

ScalaScala

Scala Scala –– Another WayAnother Way

Scala: Putting It TogetherScala: Putting It Together

new BufferedReader(new InputStreamReader(System.in))

.readLine()

.split(" ")

.groupBy(_.sorted)

.values

.filter(_.length > Integer.parseInt(args(0)))

.toList

.sortBy( - _.size )

.elements

.foreach(winner => println(winner.size + ": " + winner.toList))

new BufferedReader(new InputStreamReader(System.in)).readLine().split(" ").groupBy(_.sorted).values.filter(_.length > Integer.parseInt(args(0))).toList.sortBy( - _.size).elements.foreach(winner => println(winner.size+": "+ winner.toList))

JythonJython

What is Jython?What is Jython?

• Like Java– Have access to Java standard libraries and third party libraries

• Not like Java– Language is Python; latest release conforms to Python 2.5– Dynamically typed– Choice of using procedural, object oriented, or functional

programming constructs, or a mixture of the three– Have access to the Python standard libraries and any pure

Python third party library

• Not like Python– No access to compiled Python libraries– Some library features are not available (like fork) due to the

restrictions of the JVM

alpha = lambda l : ''.join(sorted(l))

Arrays.sort(chars);

Jython: AlphagramJython: Alphagram

JavaJava

JythonJython

if (group == null)

group.add(word);

anagrams = [list(g) for k, g in

itertools.groupby(

sorted(sys.stdin.readline().split(), key =alpha),

alpha)]

Jython: Building MultimapJython: Building Multimap

JavaJava

JythonJython

winners = (f for f in anagrams if len(f) > int(sys.argv[1]))

Jython: FilteringJython: Filtering

JavaJava

JythonJython

winners.add(group);

List comprehension:

{<output>|<variables> <collection>, <filter>}

winners = sorted(winners, key = lambda t: -len(t))

Jython: SortingJython: Sorting

JavaJava

JythonJython

Jython: PrintingJython: Printing

JavaJava

JythonJython

for winner in winners:

print '%i: %s '%(len(winner), winner)

Jython: Complete ExampleJython: Complete Example

import itertools

alpha = lambda l : ''.join(sorted(l))

winners = [

f for f in

sorted (

[list(g) for k, g in

itertools.groupby(

sorted(sys.stdin.readline().split(), key = alpha),

alpha)],

key = lambda t: -len(t) )

if(len(f) > int(sys.argv[1]))]

print '%i: %s '%(len(winner), winner)

import itertoolsalpha = lambda l : ''.join(sorted(l))

winners = [f for f in sorted ([list(g) for k, g initertools.groupby(sorted(sys.stdin.readline().split(), key=alpha),

alpha)], key = lambda t: -len(t) )

for winner in winners:print '%i: %s '%(len(winner), winner)

import itertoolsalpha = lambda l : ''.join(sorted(l))

winners = [f for f in sorted ([list(g) for k, g initertools.groupby(sorted(sys.stdin.readline().split(), key=alpha),

alpha)], key = lambda t: -len(t) )

for winner in winners:print '%i: %s '%(len(winner), winner)

Jython: A Jython: A ““SimpleSimple”” ExampleExampleimport java.util.*;public class Anagram {public static void main(String[] args) {int minGroupSize = Integer.parseInt(args[0]);Map<String, List<String>> anagrams = new HashMap<String, List<String>>(); for (Scanner s = new Scanner(System.in); s.hasNext();) {String word = s.next();String alphagram = alphagram(word);List<String> group = anagrams.get(alphagram);if (group == null)anagrams.put(alphagram, group = new ArrayList<String>());

def sort_string(buf):

l = list(buf)

l.sort()

return ''.join(l)

def get_words():

fp = open('dictionary', 'r')

words = [ l.strip() for l in fp.readlines() ]

words.sort()

return words

def get_lists_of_size(list_lists, min_size):

return [ l for l in list_lists if len(l) >= min_size ]

def main():

all_anagrams = {}

for word in get_words():

key = sort_string(word)

if all_anagrams.has_key(key):

all_anagrams[key].append(word)

all_anagrams[key] = [word]

list_lists = all_anagrams.values()

winners = get_lists_of_size(anagrams, 8)

winners.sort(cmp=lambda x,y: cmp(-len(x), -len(y)))

print "%d : %s" % (len(winner), winner)

You can w

rite Ja

ny language!

ClojureClojure

What is Clojure?What is Clojure?

• Like Java– Not much, really– Data structures implement the read-only portion of Collection– Functions implement Runnable & Callable

• Not like Java– Dynamic, functional language– Not object-oriented (!)– Persistent, immutable data structures– Lazy sequence abstraction– Software transactional memory– Multimethods and ad-hoc hierarchies– Macros

• Compared to Common Lisp/Scheme– Persistent, immutable data structures– First-class Vectors, Sets, and Maps– Focus on concurrency– No tail call optimization; explicit calls to recur and trampoline required

(defn alphagram [word] (apply str (sort word)))

Arrays.sort(chars);

Clojure: AlphagramClojure: Alphagram

#(apply str (sort %))

JavaJava

ClojureClojure

Clojure with placeholder syntaxClojure with placeholder syntax

(fn [word] (apply str (sort word)))

Clojure anonymous functionClojure anonymous function

(group-by alphagram (iterator-seq (java.util.Scanner. System/in)))

if (group == null)

group.add(word);

Clojure: MultimapClojure: Multimap

(group-by #(apply str (sort %))

(iterator-seq (java.util.Scanner. System/in)))

JavaJava

ClojureClojure

Clojure with placeholder syntaxClojure with placeholder syntax

winners.add(group);

Clojure: Filtering And SortingClojure: Filtering And Sorting

JavaJava

ClojureClojure

(def words-in (iterator-seq (java.util.Scanner. System/in)))

(defn select-anagrams [words]

(sort-by #(- (count %))

(filter #(> (count %) min-group-size)

(group-by alphagram words)))))

Clojure: PrintingClojure: Printing

JavaJava

ClojureClojure

(doseq [winner (select-anagrams words-in)]

(println (count winner) ": " winner))

(let [alphagram #(apply str (sort %))

map (group-by alphagram words-in)

filtered (filter #(> (count %) min-group-size) (vals map))

winners (sort-by #(- (count %)) filtered)]

(doseq [winner winners] (println (count winner) ": " winner)))

(defn alphagram [word] (apply str (sort word)))

(def min-group-size (Integer/valueOf (first *command-line-args*)))

(def words-in (iterator-seq (java.util.Scanner. System/in)))

(defn select-anagrams [words]

(sort-by #(- (count %))

(filter #(> (count %) min-group-size)

(group-by alphagram words)))))

(doseq [winner (select-anagrams words-in)]

(println (count winner) ":" winner))

Clojure: Complete ExampleClojure: Complete Example

Keeping it functionalKeeping it functional

Let there be bindings!Let there be bindings!

(defn alphagram [word] (apply str (sort word)))(def min-group-size (Integer/valueOf (first *command-line-args*)))

(def words-in(iterator-seq (java.util.Scanner. System/in)))

(defn select-anagrams [words] (sort-by #(- (count %)) (filter #(> (count %) min-group-size) (vals(group-by alphagram words)))))

(doseq [winner (select-anagrams words-in)](println (count winner) ":" winner))

(defn alphagram [word] (apply str (sort word)))(def min-group-size (Integer/valueOf (first *command-line-args*)))

(def words-in(iterator-seq (java.util.Scanner. System/in)))

(defn select-anagrams [words] (sort-by #(- (count %)) (filter #(> (count %) min-group-size) (vals(group-by alphagram words)))))

(doseq [winner (select-anagrams words-in)](println (count winner) ":" winner))

JRubyJRuby

What is JRuby?What is JRuby?

• Like Java– Have access to Java standard libraries and third party

libraries– Runs in a JVM

• Not like Java– Language is Ruby; latest release conforms to Ruby 1.8.7– Dynamically typed– Can compile to class files– Have access to the Ruby standard libraries and any pure

Ruby third party library

• Not like Ruby– No access to Ruby native-C API– No access to Ruby continuations

word.chars.sort.join

Arrays.sort(chars);

JRuby Example: AlphagramJRuby Example: Alphagram

JavaJava

JRubyJRuby

anagrams = words.group_by { |word| word.chars.sort.join }

if (group == null)

group.add(word);

JRuby: MultimapJRuby: Multimap

JavaJava

JRubyJRuby

filtered = anagrams.values.select {|array| array.length > 4 } winners = filtered.sort_by { |array| array.length }winners.each {|each| puts “#{each.size} : #{each.join(‘, ‘)}"}

winners.add(group);

JRuby: Filtering, Sorting, PrintingJRuby: Filtering, Sorting, Printing

JavaJava

JRubyJRuby

JRuby: Complete ExampleJRuby: Complete Example

anagrams = words.group_by {|word| word.chars.sort.join}

filtered = anagrams.values.select {|array| array.length > 4}

winners = filtered.sort_by { |array| array.length }winners.each {|each| puts “#{each.size} : #{each.join(‘, ‘)}"}

JRuby: Complete Example JRuby: Complete Example –– LetLet’’s Make It Betters Make It Better

class String

def collation

self.chars.sort.join

class Symbol

def to_proc

proc { |*args| args[0].send(self, *args[1...args.size]) }

module Enumerable

def partitioned_with(&transformer)

group_by(&transformer).values

def longer_than(size)

self.select {|e| e.length > size}

def sorted_by_size

self.sort_by(&:length)

JRuby: Better Complete ExampleJRuby: Better Complete Example

groups = words.partitioned_with(&:collation)

winners = groups.longer_than(4).sorted_by_size

winners.each{|each| puts "#{each.size}: #{each.join(', ')}"}

TakeawaysTakeaways

• JVM provides a robust, industrial strength, scalable platform

• You can take advantage of JVM and the rest of the Java ecosystem without the complexity of Java the language

• Don’t have to wait for Java to adopt the features already available in other languages: closures, dynamic capabilities, rich, humane interfaces

• Not all languages are enterprise ready– These languages are still worth looking into

• Pragmatic Programmer advice: Learn a new language every year. When you learn a new language, you learn a new way to think.

The EndThe End

Alternate JVM Languages

Technology

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