This tutorial will focus on IntelliJ IDEA Community Edition 2019. You will need an IDE (Integrated Development Environment) such as IntelliJ or Eclipse to read or create class files. A few Java tutorials to try are w3schools (web and mobile), SoloLearn (web and mobile), and kodevelopment(web). Class files are specific to the Java programming language.Minecraft mods consist of jar files (example: yournewmod.jar) which contain class files, JSON files, and image files, to name a few of the most common. In any case, this guide will eventually cover only the most basic elements of creating an item and creating an entity (a moving thing like a villager, sheep, zombie, etc.), and distributing the resulting mod package. Or perhaps you want to 'fork' a favorite mod to update for newer versions of Minecraft. Or look into how to make a resource pack if you simply want to customize textures (colors and designs), models, music, sounds, languages, splashes, fonts, or the end poem. If you simply want to add custom advancements, functions, loot tables, structures, recipes or tags to your game, look into how to make a Data pack, which does not require programming. Presumably, you already have an idea for a mod you want to create. Mods (short for 'modifications') can modify or add items, blocks, entities, and much more. 3.4.1 Custom Layers over Vanilla Textures.
