Hey, I just bought a course on programming Minecraft plugins. I did everything right, but I make a mistake. What can that be? My sb is correct.
Select Java as the project SDK.
Go to Project Structure, and ensure that Platform Settings [SDK's] has your path for Java set, in my case / usr / lib / jvm / java-6-sun (should be at least Java 8 for you), and then the main fix:
Set the Project Settings [Project] -> Project SDK to your current JDK. I had mine set to none for the project I was working on. Therefore, no java, no string, no primitive types, no nothing.
http://peterpants.blogspot.com/2011/04/intellij-idea-frustrations-with-cannot.html
I guess you haven't set your JDK for the project yet. Just have to set the JDK (I would recommend Java 8 for MC plugins). Then everything goes.
Mfg Jannick (L1nd)
PS: you can find out how to do this on the Internet, just do "change jdk intellij" and you're done.