Scala Resource Links Getting started

Learning Methodology

When I learn new programming languages I first choose a non-trivial programming problem and then develop pieces of that system in the new language then go back and re-factor as I learn more.   Solving a real problem with the language is the fastest way I have found to gain demonstrated competence in a new language.

I first discover examples of the key things you need to accomplish in any distributed system such as fetching a remote web page,  parsing a delimited file, Sorting an array.  This document contains links to information I discovered along the way.  Let me know of links you think should be added.

Helpful Scala Links

Items that should be considered must Read are prefixed with **.
Items prefixed **# specify recommended study order

Joe’s Complete Examples




Quick Reference

Language Comparisons

Style & Best Practices

Install Scala Tool-set

Most common issues arise from bad version of Java.  Install a new JDK first and remove old Java if feasible.



Java Inter-operation

Data Structures




Web Client

O.O. programming




Functional Programming

Reactive Programming


Command Line

Netty Server

Play Web Server

Other Servers

Play Hosting

Hosting Companies

 Elastic Search Hosting

Building Web apps often requires search.   We can always spin up a AWS instance or a dedicated node from but these vendors provide pre-installed elastic search.


Machine Learning


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Scala in Browser / Client Side Scala

  • tryScala Interactive execution of Scala in applet on browser
  • Scala in browser getting started with Scala.js.  Compiles scala to javascript that runs in browser.
  • TODO: Ajax example in scala.js
  • TODO: DOM find element in scala.js
  • TODO: DOM add element in scala.js
  • TODO: Modify CSS dynamically
  • TODO: Inserted generated HTML into DIV.

Groups and Blogs

Googles Scala users group

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,Sample of using from URL direct copy to fix binary issues with URL file donwload


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We provide consulting services with a specialty in solving complex distributed problems.  Please contact us if you need help. joeeatbayesanalytic  phone number

Overcome Class not found when compiling from command line.

If you compile a class or package from command line Scala will not find it unless you add -classpash . to your command line.    This tells scala to search your current directory.

 Example:    scala -classpath . readHGTElevationGenJPG.scala 


 package mylibs.sample {
 object util { 
 def printAString( aStr : String) = {
 println("printAString() " + aStr )


import mylibs.sample
sample.util.printAString("I am a string")


call scalac exSampleLibrary.scala

echo Using implied class path from enviornment variable
echo Seems to fail with error can not find import under
echo some conditions but have not been able to reliably 
echo predict when it will fail.

call scala exSampleLibraryTest.scala

echo Now try it with our class path explicit  By adding
echo the class path it manually it never seems to fail
scala -classpath . exSampleLibraryTest.scala

NOTE:   I use the mylibs. or something similar to keep all the class files junk generated by the compliler out of my main source directories.   It also makes it easy to avoid saving those binaries with the git ignore file.

I tend to distrust IDE.  Or more specifically i like to be able to build everything explicitly and know what the underlying tools are doing before depending and build packages.  I blew a a couple hours on this because I expected the scala command line to search the java CLASSPATH for resolving module names.   I always have my java CLASSPATH set with .;./lib;..;../lib;../..;../../lib so I can have sub projects that depend on more general library modules.  I would have expected scala to find my locally compiled modules this way but it didn’t.


Random Notes

There is no char in Scala they are treated as strings



  bluex = { 
     'name': 'Johny Blue',
     'weight' : 170,
     'height' : 62 


Define class constructor values with var to allow mutable elements as class attributes.

Play Routing

play – Accessing files saved in the public directory

Using the Standard play 2.4 seed you can add a new file under the /public directory such as sample.txt  This can be retrieved using the URI:   without having to change the routes file.

play – Creating a Alias to Directory inside of the project

Creating an alias for the public directory  under  conf/routes add the line GET     /s/*file                    controllers.Assets.versioned(path=”/public”, file: Asset)  which allows the  sample.txt file stored in public/sample.txt to be accessed as

play – Creating an alias to file external to the Play application

I used this because I need to reference stock and forex data files that can be hundreds of gigabytes and do not have sufficient storage to duplicate them in different directories for different projects an when running on windows the symbolic link doesn’t work.  Add the following to the file  conf\router

 GET     /forex/*file     ”/stock/jstrade”, file)

Retrieved the file existing file actions.txt with view-source: