Java with Greenfoot Lesson 1: Hello Wombats!

If you are familiar with Scratch and would like to learn more on programming. Java with Greenfoot is a great choice.

In this lesson, we will test the water by looking at a sample Greenfoot project called “wombats”.

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To open the sample Greenfoot project, do “Scenario”->”Open”

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Browse to the Greenfoot directory and open “scenarios”, and select “wombats”.

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You will see a Greenfoot project that looks as followed.

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If you’ve followed the Scratch series (if you have not, I would strongly recommend), then it should be quite obvious to you that the Greenfoot has similar interface to Scratch.

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To “populate” the world, right click at the “wombatWorld” on the top of the Current Program panel. Then select “void populate()” from the drop-down list.

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You would see two bears and six leaves shown up in the world. Click the “Run” button to start the program. Once the program starts, these two bears will move about finding leaves to eat. Obviously, they are vegetarian grizzly bears. The game/program will end when all leaves are gone.

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These two poor bears are too hungry; let’s give them more leaves.

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An window would pop up, asking how many random leaves to add. Enter “10” and click “OK”.

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Ten leaves would be added randomly.

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We are ready to run the program now. To run the program step by step, click “Act”. To run the program continuously, click “Run”.

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You can view the Scenario Information by clicking the highlighted button.

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Next, we can change the Actor’s image. Right click on the Wombat button and select “Set image” from the drop-down menu.

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Select an image you like. I selected the Linux Penguin named “tux.png”. Click OK to save.

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Also change the Leave’s image. I changed it to the image of a strawberry.

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When done, click “Compile all” button to recompile the program. To compile a program just means to build a program executable.

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To run the modified program, we will repopulate the world and restart the program. To populate the world, right click wombatWorld title above the program view and select “void populate()” from the drop down list. Then click the “Run” button to run the program. Also, you can add more strawberries by selecting the “void randomLeaves(int howMany)” from the drop-down list.

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