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Note: the instructions at this link are good but things have changed a bit for Forge 1.7: http://www.minecraftforge.net/wiki/Crafting_and_Smelting

Different types of mods require different types of code. One of the easiest type of mod to add is a crafting recipe. We will write one to turn some dirt into diamonds.

The code for this goes into the init function:

What this does:

• Create a new ItemStack called dirtStack with a single dirt block
• Create a new ItemStack called diamonds10 with 10 diamond blocks
• Add a new recipe to the game that will produce this stack of 10 diamonds, when you lay out the dirt in the shape specified: x in the shape is where the dirt blocks have to go.

We can also have shapeless recipes (where it doesn’t matter where you put blocks), which are even simpler to write:

GameRegistry.addShapelessRecipe(
new ItemStack(Items.diamond, 6), new ItemStack(Blocks.dirt));

This second one creates a stack of 6 diamonds from a single block of dirt.

Previous post: ModderDojo Java Modding 5: Creating Our First Mod – The Basic Code
This concludes this series of posts on getting started with Java Modding, from ModderDojo Athenry.

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There is an example mod that does nothing in src/main/java, in the package com.example.examplemod. We will make a new one based on this.

Start by making a new package in the same folder, where we will put our own code. Click on src/main/java, then from the menu select File – New – Package, and pick a package name:

Now create a class in it: File – New – Class and give it a name. There is no need to select the “public static void main” option; we will be replacing all the code.

From in ExampleMod.java, copy all of the code, then delete all of the code in your own class and paste in the code from ExampleMod. Now make some changes:

• On the top line, change the package statement: it has to correspond to the package you created your class in. Eclipse will flag the error with a red line and its quick fix will allow you to change the package.
• On the line public class ExampleMod, change ExampleMod to the name of your class. In Java, the file name and class name have to be identical.
• Check that the @Mod statement refers to your class, not ExampleMod. Note: statements beginning with @ in Java are called annotations.
• In the body of your class, change the values of the variables MODID and VERSION.
• If you like, change the System.out.println line to print a new message to the console window, e.g. “Craft1 mod initialised.” Lots of messages are displayed in the console window when Minecraft runs; you should see your message near the end.

Now run Minecraft and see if your mod exists. The name should be there and your hello message on the console, but it doesn’t do anything because we haven’t added code for anything useful.

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Previous post: ModderDojo Java Modding 3: Getting Started With Eclipse
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Start up Eclipse and select the workspace that Forge created, in the Eclipse folder under Forge:

Note: if the workspace is empty, make sure that you ran the command gradlew eclipse and that you selected the correct folder.

Press the green Run icon: you should see messages in the Eclipse console window and Minecraft will launch and will initially have 4 mods.

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Previous post: ModderDojo Java Modding 2: Setting Up Your Development Environment
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While waiting for Forge to install, let’s try out Eclipse.

If this is your first time running it, you will be prompted to create a workspace: the default location is fine

The first time, a Welcome screen appears, which you can X to close.

Java code belongs in classes, classes are organised in projects, and projects are in a workspace. In Eclipse, you can only have one workspace open at a time, but it can have multiple projects in it and each one can have multiple classes.

Create a new Java project: File – New – Project… then expand Java and select Java Project

Enter a project name, e.g. Test:

If you are asked to switch to the Java Perspective, say yes.

To create a first program class file, select File – New – Class

Give the class a name (no spaces allowed), and tick the box at “public static void main”, as this will create some initial code for you:

You now have a starting piece of code:

Under the “TODO” comment (which you can delete or replace with a comment of your own), write a line of code to put up a message box:
JOptionPane.showMessageDialog(null, “Hello world”);

A red line will appear at JOptionPane, as it is not recognised; hover over it and select the fix “import JOptionPane”, which will add an extra line at the  top.

Alternatively (or as well), you could print a line to the system output, which goes the console window – that’s the one at the bottom of the screen in Eclipse:
System.out.println(“Hi there”);

Press the Save icon and then the green Run icon to run your first program:

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