In here,the kata test will call your function and check what you return.
And System.out.println() will just print to console, won't return anything.

Not an issue. Not even a question either, because this is a basic language features question, not a kata question.

Please consult the basic language features of your language.

public class EvenOrOdd {
    public static String even_or_odd(int number) {
        //Place code here
        
    }
}

That's the initial code for java, you don't need to ask the user for input in CW, your function takes an int as parameter.