Hello fellow Ubuntu users,

I am trying to learn how to write modifications to Minecraft. In order to follow the tutorial I am using, I need to run a "gradlew". The command is as follows

./gradlew setupDecompWorkspace eclipse

This yields the following

ERROR: JAVA_HOME is set to an invalid directory: /usr/local/java/jdk1.8.0_20



Please set the JAVA_HOME variable in your environment to match the

location of your Java installation.

Obviously I don't know what to do or even what this means. Any help is much appreciated.