class Test {
        public static void main(String[] args) {
            System.out.println("Hello world");
        }
    }

    javac Test.java
    java Test

* Class is in file with the same name ¯\_(ツ)_/¯ and contains functions (maybe it'll help me later in organizing code?).

* Command line arguments (not strictly necessary concept but not too problematic either)

* Types - why is there String[] in the definition? (A must have in a statically typed language anyway)

* void - the function doesn't return anything (OK)

* public (not OK, some magic here)

* static (not OK, some magic here)

* Compilation vs. run step (a must have in a compiled language)

So IMHO there are just two concepts that could be thrown away. Or three, if you accessed CLI args from a library. But the meaning of public and static will come naturally when the students will learn about OOP.

Sounds like excellent training for a long and successful career in enterprise Java.

  > * access modifiers (public/private)

To be super thorough, you would also have to understand:

- semicolons (and the related issue of newlines being semantically equivalent to normal spaces)

- naming conventions (to explain why it's not "System.Out.Println" and "Main")

If someone applying for an architecture degree or engineering degree is required to have basic drawing skills and basic math knowledge, why we shouldn't assume the same for CS?

If I was a teacher and I'm going to teach someone what a linked list is, or what a binary tree is, I can of course use natural language and drawing, I can use abstract algebraic concepts.

But the student should be also able to construct said structures and observe how they work. The same for any other concept.