How can I catch the wrong format of input and let the user re-write it?

[native sedge]

I have following code:
`
public class HumanPlayer implements Player {
private final PrintStream out;
private final Scanner in;

public HumanPlayer(final PrintStream out, final Scanner in) {
    this.out = out;
    this.in = in;
}

public HumanPlayer() {
    this(System.out, new Scanner(System.in));
}

@Override
public Move move(final Position position, final Cell cell) {
    while (true) {
        out.println("Position");
        out.println(position);
        out.println(cell + "'s move");
        out.println("Enter row and column");
        final Move move = new Move(in.nextInt(), in.nextInt(), cell);
        if (position.isValid(move)) {
            return move;
        }
        final int row = move.getRow();
        final int column = move.getColumn();
        out.println("Move " + move + " is invalid");
    }
}

} `
Is there any way to let user correct their input? (for example, he will have the opportunity to input values again if he accidentaly wrote "hello world" instead of numbers)

[karmic epoch]

<@&987246399047479336> please have a look, thanks.

[karmic epoch]

Detected code, here are some useful tools:

Formatted code

I have following code : `public class HumanPlayer implements Player {
  private final PrintStream out;
  private final Scanner in;
  public HumanPlayer(final PrintStream out, final Scanner in) {
    this .out = out;
    this .in = in;
  }
  public HumanPlayer() {
    this (System.out, new Scanner(System.in));
  }
  @Override
  public Move move(final Position position, final Cell cell) {
    while (true) {
      out.println("Position");
      out.println(position);
      out.println(cell + "'s move");
      out.println("Enter row and column");
      final Move move = new Move(in.nextInt(), in.nextInt(), cell);
      if (position.isValid(move)) {
        return move;
      }
      final int row = move.getRow();
      final int column = move.getColumn();
      out.println("Move " + move + " is invalid");
    }
  }
}
`Is there any way to let user correct their input ? (for example, he will have the opportunity to input values againif he accidentaly wrote"hello world"instead of numbers)

[thin stag]

u "just" need to make a simple loop that repeats it

i.e. a classic
while (invalid) { read input }

ideally move it into a helper method to not clutter ur code

[somber ruin]

hi there!

can you show us what your main() looks like ?

[gray skiff]

if u only need numbers, u can check parsing the input to the integer using try catch block, if exception occurs while parsing, continue the while loop used for input, if both abe to parse to integer, u can store and break

[native sedge]

yes, but how should i parse if input is integer or not? by taking in.nextInt()?

[thin stag]

nah

u have to attempt parsing it and catch the exception

its a bit annoying

see here: #snippets message

[native sedge]

yes, but i have 2 or 3 numbers in input line...

[thin stag]

well, u have to split the input and parse each of them individually with the linked method

[gray skiff]

take the input as a string, divide it, pass those into a func which tried to parse them, if it retuns true, bingo, if not, continue the input loop again

[native sedge]

can i do this by taking next with scanner?..

[native sedge]

yes, i do this, but i can't use split

[gray skiff]

why?

[thin stag]

no

if u call nextInt() and there is no int, scanner throws a NoSuchElementException

well, i guess u could catch that as well and then do ur repeat stuff

but still, not ideal

[native sedge]

teacher doesn't allow that

and string tokenizer as well

[woeful stag]

It won't really work tho

[gray skiff]

if u can't use split, u can loop around the input and validate each character

this will be too easier

[thin stag]

u can also use next() instead of nextInt()

and then attempt to parse with the shown method

but that also wont work if the user only inputs one thing

[woeful stag]

Well, you will have to use next() then

[thin stag]

the safest and easiest route would be to use nextLine() and then split by space and then check length and attempt to parse both as int

if u cant do that, it will be a bit annoying

[native sedge]

yes, but will it throw exception if there's no second input or return "null"?

[thin stag]

exception

if u tell scanner to read sth and its not there or incorrect, ull get NoSuchElementException

and if ur not allowed to use split, u have to go that route

unless u want to implement split manually urself

with a combination of find and substring

[gray skiff]

or just traverse it i guess lol

[thin stag]

its still fairly straightforward, just a bit more cumbersome

perhaps 15 lines of code all together, for the entire validate/repeat thing

[somber ruin]

i'd suggest to use do..while

I like it in such programs

to give the user the 1st time to enter something, and repeat as long as it's invalid

[thin stag]

thats not the problem at hand though

the problem is the validation of multiple inputs in a single line

while sticking to the teachers constrains

[somber ruin]

i think using sc.hasNext()

[thin stag]

stick to nextInt instead

https://i.imgur.com/b7WyIby.png

this is one case

and this the other:

https://i.imgur.com/fg7rebL.png

so all u need to do is call nextInt() and if u get one of those 2 exceptions, it failed

no exception and its correct

if it failed, dont forget to call nextLine() once to purge the rest of the input

then loop into the next round

but step by step

get started and then share where ur stuck at, or is sth unclear still? 🙂 @native sedge

[native sedge]

ok, i will try, thank you 😄