Install Forge

(Recommend Eclipse, some api lost in IntelliJ with the latest version)

For Mac OSX user, the cmd is "./gradlew setupDecompWorkspace" instead of gradlew setupDecompWorkspace

1. Obtain a source distribution from forge’s files site. (Look for the Mdk file type, or Src in older 1.8/1.7 versions).
2. Extract the downloaded source distribution to an empty directory. You should see a bunch of files, and an example mod is placed in src/main/java for you to look at. Only a few of these files are strictly necessary for mod development, and you may reuse these files for all your projects These files are:

• build.gradle
• gradlew.bat
• gradlew
• the gradle folder

3. Move the files listed above to a new folder, this will be your mod project folder.
4. Open up a command prompt in the folder you created in step (3), then run gradlew setupDecompWorkspace. This will download a bunch of artifacts from the internet needed to decompile and build Minecraft and forge. This might take some time, as it will download stuff and then decompile Minecraft. Note that, in general, these things will only need to be downloaded and decompiled once, unless you delete the gradle artifact cache.
5. Choose your IDE: Forge explicitly supports developing with Eclipse or IntelliJ environments, but any environment, from Netbeans to vi/emacs, can be made to work.

• For Eclipse, you should run gradlew eclipse - this will download some more artifacts for building eclipse projects and then place the eclipse project artifacts in your current directory.
• For IntelliJ, simply import the build.gradle file.

6. Load your project into your IDE.

• For Eclipse, create a workspace anywhere (though the easiest location is one level above your project folder). Then simply import your project folder as a project, everything will be done automatically.
• For IntelliJ, you only need to create run configs. You can run gradlew genIntellijRuns to do this.