Category Archives: Greenfoot

Stride – A new programming language for beginners

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At the Greenfoot headquarters, we – that is: Neil Brown, Amjad Altadmri and myself – have recently worked on creating a new language within the Greenfoot environment: Stride.

The interesting thing about Stride is not so much the language design itself, but its interaction design: editing programs involves different interactions than existing editors.

The goal is that Stride sits halfway between block-based systems (such as Scratch, AppInventor, PencilCode, Alice, etc.) and text-based editors (such as Java or Python), maintaining advantages of both.

I will start a series of posts (text and/or video) here over the next few weeks trying to tell you what Stride is and why you should care. In the meantime, you can get Greenfoot, install it, and have Stride ready to go when the introduction here starts. Stride is built into Greenfoot from version 3 onwards.

Check back soon for the first overview video.

Joy of Code videos in German

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Do you want to learn programming with Greenfoot? Do you speak German? Is your German better than your English?

Then this may be your lucky day.

Frajo Ligmann, a school teacher near Aachen, Germany, has started to produce German language versions of the Joy Of Code videos. At time of writing, he has produced six videos already, which you can see on his Youtube channel. And he is working on more, which should appear as time goes on.

Producing videos is a lot of work and very time intensive, so be a bit patient if you’re itching to see more. If you’re happy to watch these in German, bookmark his page and leave him a comment, either on his page or right here below this post.

Many thanks to Frajo Ligmann for this amazing contribution to our community!

 

Do you want to work on BlueJ/Greenfoot? We’re hiring!

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The BlueJ/Greenfoot team are quite a small outfit (currently four people), but we are looking to hire two more team members.

The official job advert is here, but there’s a better starting point if you’re interested: Neil, one of our team members, has just written a blog post about these two new positions. Read this first, and then get in touch if you think this might be for you!

JoC #33: Playing Breakout! Collision detection

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      Finagles’ 8th Rule: Teamwork is essential; it allows you to blame someone else.

Today, we’re finally getting our breakout game into a playable state! Yes!!

See how to implement functionality to recognise when the ball hits a block, and make the block disappear. This is really the centrepiece of our program – from now on, everything else is detail.

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Concepts discussed: collision detection, removing an object from the world

Download (scenario as of beginning of this episode): breakout-v7.zip

JoC #32: Pretty pictures with while loops

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      90% Rule of Project Schedules: “The first 90% of the task takes 90%
      of the time, and the last 10% takes the other 90%.”
            — (source unknown) 

One more time, discussions of loops.

Loops are such an important concept, and there are so many variations, that it is really important to get practice with them and get them properly into your head. To this end, we’re looking one more time at loops here before moving on to some new concepts in the next episode.

Today, we’re using a really important, fundamental loop pattern: A while loop with a simple loop counter. It looks like this:

    int i = 0;
    while (i < NUMBER)
    {
        doSomething();
        i = i + 1;
    }

Watch the video, and try to memorize this pattern. It will come in handy later!

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Concepts discussed: loops, while loop

Download (scenario as of beginning of this episode): breakout-v6.zip

JoC #31: More loopiness

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      The First Law of Programmer Creativity: “The cost of software maintenance 
      increases with the square of the programmer’s creativity.”
            — (source unknown) 

We continue with our breakout scenario, an also with our investigation of loops. Jumping right ahead, I show you both how to write a nested loop, and why and how never to do it.

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Concepts discussed: loops, while loop

Download: breakout-v5.zip

JoC #30: Introduction to loops

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      Whatever begins, also ends.
            — Seneca
      (Seneca obviously didn’t know about getting your loop condition wrong …  — mik)

Today, we are introducing a new concept: loops. Or, if you want to know more precisely: the while loop.

But, as always, we’re not doing this by just talking about the theory in a vacuum – we actually need it to progress with one of our projects, the Breakout game that we have seen before.

Loops are a concept fundamental to all programming, so if you are a learner, pay close attention. You will need this again later!

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Concepts discussed: loops, while loop

JoC #29: Viewer questions: timers

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      Time is an illusion. Lunchtime doubly so.
            — Douglas Adams

We are starting a new, probably more or less regular, thing today: answering viewer questions.

In the first of the Q&A episodes, I am talking about timers: How to arrange something to happen after a specific time delay. This principle is generally useful for many games and simulations. We also get  bit more practice with int variables.

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Concepts discussed: time delay, variables, counting


JoC #28: Return of the object interaction

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      If life gives you lemons – keep them. Because, hey. Free lemons.
            — Anonymous

In this episode, we’re continuing from the last episode’s theme and investigate and compare an alternative structure for making our Ball and Counter objects cooperate. We also have a first brief look at casting.

Recognising alternatives is a good skill, and it slowly eases us into discussions about code quality, which we will get to in more detail later.

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The download today (below) is the scenario as it is at the end of this episode. However, try to add a counter into one of your own scenarios to make sure you are fully taking in what’s going on here.

Concepts discussed: object interaction, casting, score counting

Download: breakout-v3.zip  (the scenario at the end of this episode)

JoC #27: Object interaction – a second look

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      Daring ideas are like chessmen moved forward; they may be beaten,
      but they may start a winning game.
            — Goethe

In this and the next episode, we’re looking a bit more into how to set up object structures, and how to get them to interact. This is one of the most fundamental concepts of object-oriented programming, so you need to get your head around this.

We discuss this here with the example of integrating our counter object into a scenario.

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Concepts discussed: object interaction, object references, score counting, constructors, fields

Download: breakout-v2.zip  (the scenario at the end of this episode)