The New Joy of Code – 01: Introduction

Finally it is here: The first of the New Joy of Code programming series.

In this series of videos I will show you how to program in Greenfoot and Stride. Later in the series, we will also get to programming in Java. But ultimately, what you will learn are the principles of object-oriented programming, which you should then be able to apply to any language.

This first episode shows you what Greenfoot is, and what Stride looks like.

Download Greenfoot here.

Check back soon for more episodes.


Joy of Code videos in German

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!


JoC #33: Playing Breakout! Collision detection

      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 discussedcollision detection, removing an object from the world

Download (scenario as of beginning of this episode):

JoC #32: Pretty pictures with while loops

      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)
        i = i + 1;

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

Download video

Concepts discussedloops, while loop

Download (scenario as of beginning of this episode):

JoC #31: More loopiness

      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 discussedloops, while loop


JoC #30: Introduction to loops

      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 discussedloops, while loop

JoC #29: Viewer questions: timers

      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 discussedtime delay, variables, counting

JoC #28: Return of the object interaction

      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 discussedobject interaction, casting, score counting

Download:  (the scenario at the end of this episode)

JoC #27: Object interaction – a second look

      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 discussedobject interaction, object references, score counting, constructors, fields

Download:  (the scenario at the end of this episode)