SimpleIO in JEP draft 8323335

[Brian Goetz]

I think you are counting characters and not counting concepts.

Scanner has a ton of complexity in it that can easily trip up 
beginners.  The main sin (though there are others) is that input and 
parsing are complected (e.g., nextInt), which only causes more problems 
(e.g., end of line issues.)   Reading from the console is clearly a () 
-> String operation.  The input() method does one thing, which is get a 
line of text.  That's simple.

Integer.parseInt (or, soon, patterns that match against string and bind 
an int) also does one thing: convert a string from int.  It may seem 
verbose to have to do both explicitly, but it allows each of these 
operations to be simple, and it is perfectly obvious what is going on.  
On the other hand, Scanner is a world of complexity on its own.

Console::readLine is nice, but first you have to get a Console. ("Why 
can I print something without having to get some magic helper object, 
but I can't do the same for reading?")  What we're optimizing for here 
is conceptual simplicity; the simplest possible input method is the 
inverse of println.  The fact that input has to be validated is a fact 
of life; we can treat validation separately from IO (and we should), and 
it gets simpler when you do.

On 2/18/2024 4:12 PM, Cay Horstmann wrote:
> I would like to comment on the simplicity of 
> https://openjdk.org/jeps/8323335 for beginning students.
>
> I am the author of college texts for introductory programming. Like 
> other authors, I introduce the Scanner class (and not Console) for 
> reading user input. Given that students already know about System.out, 
> it is simpler to call
>
> System.out.print("How old are you? ");
> int x = in.nextInt(); // in is a Scanner
>
> than
>
> int x = Integer.parseInt(console.readLine("How old are you? "));
>
> or with the JEP draft:
>
> int x = Integer.parseInt(input("How old are you? "));
>
> Then again, having a prompt string is nice too, so I could imagine 
> using the Console API with Integer.parseInt and Double.parseDouble, 
> instead of Scanner.nextInt/nextDouble.
>
> But why have a third API, i.e. "input"?
>
> I think there are two feasible directions. Either embrace the Scanner 
> API and next/nextInt/nextDouble/nextLine, or the Console API and 
> readLine. Adding "input" into the mix is just clutter, and ambiguous 
> clutter at that. At least readLine makes it clear that the entire line 
> is consumed.
>
> Cheers,
>
> Cay
>
> -- 
>
> Cay S. Horstmann | http://horstmann.com | mailto:cay at horstmann.com