IntelliJ IDEA gives error when I use console.printf or console.readLine. But it works in Treehouse...?

The problem is that the Console class does not work in most Java IDEs due to the way they run your program. This stackoverflow post provides a more detailed explanation as to why it does not work if you are curious. If you compiled your program in IntelliJ and ran it in a console manually then it would work fine.

This means that you have to use alternative ways to print and get input when working in your IDE.

To print you can use System.out instead of console like this:

System.out.println("Text you want to be printed to console");

System.out also has a printf and print method just like the Console class, that works in the same way as the Console equivalents

And to get input you can use this code:

Scanner scanner = new Scanner(System.in); // Write this in your code once
String input = scanner.nextLine(); // Then use scanner.nextLine as a substitute for console.readLine