How to make an Int only accepts integers?

Question

I have this problem where I want to identify the clients with in id. I want that Id only to be a number. Any ideas? Thanks in advance.

    int id = IBIO.inputInt("Enter the clients id:");

    boolean Clientexists = clientsAdm.existsClient(id) > 0;
    if (Clientexists != true) {

        String name = IBIO.inputString("Enter the client name:");
        String surname = IBIO.inputString("Enter the client surname:");
        String address = IBIO.inputString("Enter the client address:");
        String phone = IBIO.inputString("Enter the client phone:");
        String CreditCard = IBIO.inputString("Enter the type of card the client has: green, red or gold");  //asegurar que solo se ingrese RED, GREEN or GOLD
        Client c = new Client(name, surname, address, phone, CreditCard, id);

        clientsAdm.addClient(c);
    } else {

        IBIO.output("Error, this ID already exists.");

    }

    IBIO.output("Your client has been added.");
}

What exactly do you want to do if the user doesn't enter an integer? — user202729, Jul 19 '18 at 14:17
Possible duplicate of [Decimal or numeric values in regular expression validation](https://stackoverflow.com/questions/2811031/decimal-or-numeric-values-in-regular-expression-validation) — Alex Sergeenko, Jul 19 '18 at 14:17
@AlexSergeenko Given that Java has built-in ways to check if a string is an integer, using a regex is a ***bad*** way. — user202729, Jul 19 '18 at 14:18
What exactly is the problem? And keep in mind we don't know what `IBIO` is. — Henry, Jul 19 '18 at 14:18
@Henry [Probably a library](http://ibcomp.fis.edu/ibo/IBIO.html). — user202729, Jul 19 '18 at 14:19
If the user does not enters an integer, I want to output a message, for example ("Id is not valid") — Juan Bañales, Jul 19 '18 at 14:21
So I guess the `inputInt` method fails if something other than an integer is entered? — Henry, Jul 19 '18 at 14:23
It does work. But you can enter a letter, word, or whatever and it will be saved as the id. And I want the id onle accept an integer number. — Juan Bañales, Jul 19 '18 at 14:25
You assign it to an `int` so it is a number at this point. An `int` can only store integers. What do you mean by it will be saved as the id? — Henry, Jul 19 '18 at 14:27
If the user does not enters an integer, I want to output a message, for example ("Id is not valid"). — Juan Bañales, Jul 19 '18 at 14:28
If when the programm asks "Enter id" and I enter for example "a" or "b", it will work. — Juan Bañales, Jul 19 '18 at 14:29
In case of using IBIO library please follows its source codes http://ibcomp.fis.edu/ibo/IBIO.html Seems it should work out-of-the box, it is just return 0 if not an integer was an input. — Alex Sergeenko, Jul 19 '18 at 14:43

ChRix · Answer 1 · 2018-07-19T15:28:03.400

This could work, if you gave me more details maybe I could help you better a greeting

       int id = IBIO.inputInt("Enter the clients id:");

        boolean Clientexists = clientsAdm.existsClient(id) > 0;
        if (Clientexists != true) {
                String name = IBIO.inputString("Enter the client name:");
            String surname = IBIO.inputString("Enter the client surname:");
            String address = IBIO.inputString("Enter the client address:");
            String phone = IBIO.inputString("Enter the client phone:");
            String CreditCard = IBIO.inputString("Enter the type of card the client has: green, red or gold");  //asegurar que solo se ingrese RED, GREEN or GOLD
            Client c = new Client(name, surname, address, phone, CreditCard, id);


if(id instanceof Integer) {
clientsAdm.addClient(c);
} else {
IBIO.output("Id is not valid");
}
        } else {
                IBIO.output("Error, this ID already exists.");
            }
            IBIO.output("Your client has been added.");
    }

Else you can try this:

 int id;
    try{
    id = IBIO.inputInt("Enter the clients id:");}
    catch(Exception e){
IBIO.output("Id is not valid");
    }

score 0 · Answer 2 · answered Jul 19 '18 at 15:42

If zero is an illegal input for an ID, then you can check if the ID is zero, because IBIO.inputInt(String prompt) returns zero when prompt is given a non-integer.

If zero is a legal input for an ID, then IBIO.inputInt(String prompt) cannot be used. When a non-integer is passed into IBIO.inputInt, the exception is masked, and a zero is returned. Instead, you will need to define your own method for reading a user input. You can do something like this:

static int inputIntWithRetry(String prompt) {
   int result = 0;
   int numberOfRetry = 5; // holds the number of times to reprompt the user
   boolean isInt = false; // flag for exiting the loop early if user provides a int
   for(int i = 0; i < numberOfRetry || !isInt; i++) {
      try {
         result = Integer.valueOf(
         input(prompt).trim()).intValue();
         isInt = true;
      } catch (Exception e) {
         System.out.println("Id is not valid");
      }
   }
   if (isInt) {
      return result;
   } else {
      // handle not receiving an int after 5 tries
   }
}

How to make an Int only accepts integers?

2 Answers2