This course has already ended.

Luet oppimateriaalin englanninkielistä versiota. Mainitsit kuitenkin taustakyselyssä osaavasi suomea. Siksi suosittelemme, että käytät suomenkielistä versiota, joka on testatumpi ja hieman laajempi ja muutenkin mukava.

Suomenkielinen materiaali kyllä esittelee englanninkielisetkin termit. Myös suomenkielisessä materiaalissa käytetään ohjelmaprojektien koodissa englanninkielisiä nimiä kurssin alkupään johdantoesimerkkejä lukuunottamatta.

Voit vaihtaa kieltä A+:n valikon yläreunassa olevasta painikkeesta. Tai tästä: Vaihda suomeksi.

Installing Eclipse and Scala IDE

As mentioned in Chapter 1.2, O1’s official programming environment is the Eclipse IDE and its Scala IDE plugin, which are installed on Aalto IT’s Linux workstations.

If you want to use Eclipse and Scala IDE on your personal computer, you’ll first need to install them. These tools are available for Windows, macOS, and Linux. The newer your operating system, the less likely it is you’ll run into trouble installing the tools.

Version numbers matter

Any tools you use in O1 should be compatible with version 2.12.6 of the Scala programming language. Officially, we use version 4.7 Oxygen of Eclipse and version 4.7 of Scala IDE. You’ll also need a Java toolkit (JDK); the recommended version is 8.

Follow the instructions below to install the appropriate versions. There’s a short troubleshooting section at the end of the page.

Step 1 of 4: Install a Java Toolkit

Screenshots of installing Java. (The pics are for Java 7, but installation of Java 8, which you need, is essentially identical.)


On Windows or macOS:

  1. Use this link to download Java SE Development Kit 8 (JDK). Pick the 64-bit version.
    • (You'll need to be working in a modern 64-bit operating system, not a 32-bit one. To check which kind of environment you’re in, check your operating system settings; e.g., Control Panel ‣ System in Windows.)
  2. On Windows and macOS, you can install the software by simply executing the downloaded file and agreeing when the installer asks you to approve what it’s doing.

On Ubuntu (Debian Linux), we recommend that you install Oracle’s Java environment, which isn’t available among Ubuntu’s own packages. It’s not too complicated; what you need to do is open a Terminal and enter these instructions:

  • sudo add-apt-repository ppa:webupd8team/java
  • sudo apt-get update
  • sudo apt-get install oracle-java8-installer
  • sudo apt-get install oracle-java8-set-default

You can then enter java -version to ensure that you have the correct version of Java installed.

Step 2 of 4: Install Eclipse and Scala IDE

Download the Eclipse + Scala IDE bundle, version 4.7 for your operating system.

Install the IDE and its plugin simply by extracting the archive file you downloaded into a folder of your choice:

  1. In any of the main operating systems, you should be able to double-click the archive to open it.
  2. There’s no installer that you need to run; just use your mouse to drag the archive’s contents (a folder named eclipse) to wherever you’d like to place them. For instance, on a Mac, you might want to put eclipse under the Applications folder.

Step 3 of 4: Start Eclipse

Launch Eclipse by clicking eclipse.exe (in Windows) or the corresponding app file within the eclipse folder. When prompted, pick some new folder as your O1 “workspace”: this is the folder where you’ll store the programs that you write during O1.

Step 4 of 4: Adjusting Settings

We strongly encourage you to import O1’s own preference settings, which suit the course and generally make Eclipse more pleasant to work with. Here’s how:

  1. Download the preferences file o1_2018.epf and save it on your desktop or somewhere else.
  2. In Eclipse, select File ‣ Import... ‣ General ‣ Preferences and press Next.
  3. At From preference file, indicate the location of the file you saved, o1_2018.epf.
  4. Make sure that Import all is ticked.
  5. Press Finish.

Finally, you can make it easier to use Eclipse in the future by pinning it to the task bar of your operating system so that you can launch it easily later:

  • On Windows, right-click the Eclipse icon in the task bar and select Pin this program to taskbar.
  • On macOS, you can similarly pin Eclipse to the Dock. Ubuntu has a similar feature, too.


“I launched Eclipse on Windows but just got a long error message.”

The probable cause is that you’ve installed a 64-bit version of Scala IDE but have a 32-bit version of Scala, or the other way around. Please use a modern 64-bit operating system and 64-bit versions of all the required tools.

“I installed the right version of Java, but Eclipse still won’t run on my Mac.”

Your macOS version may be old. We recommend that you update it. Java’s version 8 requires macOS version 10.8.3 (Mountain Lion) or newer.



Thousands of students have given feedback that has contributed to this ebook’s design. Thank you!

Weeks 1 to 13 of the ebook, including the assignments and weekly bulletins, have been written in Finnish and translated into English by Juha Sorva.

Weeks 14 to 20 are by Otto Seppälä. That part of the ebook isn’t available during the fall term, but we’ll publish it when it’s time.

The appendices (glossary, Scala reference, FAQ, etc.) are by Juha Sorva unless otherwise specified on the page.

The automatic assessment of the assignments has been programmed by Riku Autio, Jaakko Kantojärvi, Teemu Lehtinen, Timi Seppälä, Teemu Sirkiä, and Aleksi Vartiainen.

The illustrations at the top of each chapter, and the similar drawings elsewhere in the ebook, are the work of Christina Lassheikki.

The animations that detail the execution Scala programs have been designed by Juha Sorva and Teemu Sirkiä. Teemu Sirkiä and Riku Autio have done the technical implementation, relying on Teemu’s Jsvee and Kelmu toolkits.

The other diagrams and interactive presentations in the ebook are by Juha Sorva.

The O1Library software has been developed by Aleksi Lukkarinen and Juha Sorva. Several of its key components are built upon Aleksi’s SMCL library.

The pedagogy of using tools from O1Library (such as Pic) for simple graphical programming is inspired by the textbooks How to Design Programs by Flatt, Felleisen, Findler, and Krishnamurthi and Picturing Programs by Stephen Bloch.

The course platform A+ has been created by Aalto’s LeTech research group and is largely developed by students. The current lead developer is Jaakko Kantojärvi; many other students of computer science and information networks are also active on the project.

For O1’s current teaching staff, please see Chapter 1.1.

Additional credits for this page

This page on Eclipse was written by Otto Seppälä and Teemu Sirkiä. It’s been edited and translated by Juha Sorva.

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