"Minecraft" is written in the Java programming language, and to write code for the game, developers must learn the Java coding language first. There are many websites that offer resources for learning Java, which is where would-be "Minecraft" coders should begin, but there are also some options for shortcuts.
"ScriptCraft" is a mod that allows "Minecraft" players to code right within the game, making it easy to create and test mods instantly. Players should still have a decent understanding of the Java coding language. Most developers who create mods create them within servers to allow multiple people to test them at once. CanaryMod is a server mod that allows players to develop within the server.
If coding outside of a server, developers should have the Java SE Developers Kit and an integrated development environment, or IDE for short. Every modder should also be familiar with "ModLoader," as it makes importing mods into "Minecraft" much easier.
If players wish to skip the Java learning process, some websites allow its users to create mods without typing one single line of code. These websites have pre-made mods that users can customize and then download into a pack, which can then be imported into "Minecraft."