Do-While loop user-entered not looping

Question

int ID;

Scanner scan = new Scanner(System.in);
ID = Integer.parseInt(scan.nextLine());

do{
   System.out.println("Improper EMPID, please reenter your EMPID.\n");
   Scanner scan1 = new Scanner(System.in);
   ID = Integer.parseInt(scan1.nextLine());
}
while (ID > 999999 && ID < 10000000);

return ID;

This is a function in my main code where I attempt to have the user enter a seven digit ID.
It's supposed to loop infinitely until the user enters seven digits, however will only loop through once then exits.

I have also done this with a while loop with the same results. Something I'm not seeing here?

  Scanner scan = new Scanner(System.in);
  int id = Integer.parseInt(scan.nextLine());

  while (id >= 10000000 || id <= 999999);{
     System.out.println("Please enter your EMPID\n");
     id = Integer.parseInt(scan.nextLine());
  }


  return id;

My code now looks like this.

It will constantly loop without showing the print.

You are checking the values in the loop condition, not the amount of digits! The loop never gets entered because there is no number (-value) between 999999 and 1000000 that can be stored as `int` or `Integer`. Have a look at [this question about the amount of digits of an `int`](https://stackoverflow.com/questions/1306727/way-to-get-number-of-digits-in-an-int). You can check the value, but then only check if it is less than 10000000 to make it less than 7 digits. — deHaar, Aug 30 '18 at 14:30
deHaar, how would I be able to do that? Also I just realized it wont work as a do-while loop, so I have changed it back to a while loop — Christopher Roskind, Aug 30 '18 at 14:32

xingbin · Accepted Answer · 2018-08-30T14:38:29.427

4

You should continue the loop when the input is invalid:

while (ID <= 999999 || ID >= 10000000);

Not related to the question, but please name variables with camel case, and remove unecessary code:

Scanner scan = new Scanner(System.in);
int id = Integer.parseInt(scan.nextLine());

while (id <= 999999 || id >= 10000000) {
    System.out.println("Improper EMPID, please reenter your EMPID.\n");
    id = Integer.parseInt(scan.nextLine());
}

edited Aug 30 '18 at 14:38

answered Aug 30 '18 at 14:33

xingbin

27,410
9
53
103

I changed my code to how yours looks, however it now constantly loops and doesn't print the text. – Christopher Roskind Aug 30 '18 at 14:45
@ChristopherRoskind What did you input and what's your code now? – xingbin Aug 30 '18 at 14:46
I input the number 69152133. I will update my question with how my code currently looks. – Christopher Roskind Aug 30 '18 at 14:48
1

@ChristopherRoskind You need remove the `;` in this line `while (id >= 10000000 || id <= 999999);` – xingbin Aug 30 '18 at 14:53

score 0 · Answer 2 · answered Aug 30 '18 at 14:32

You don't check the lenght of the input, you check for the real value. You can use int length = String.valueOf(ID).lenght(); to get the lenght of an int value.
Just a hint: Don't create new scanners each time, you will confuse your self. One is just fine.

Jean-Serge Gagnon · Answer 3 · 2018-08-30T17:58:44.080

0

this logic would be better with a while loop since you first ask the user for a value and want to give them an error message only if it's wrong

such as

 Scanner scan = new Scanner(System.in);
 int ID = Integer.parseInt(scan.nextLine());
 while (!ID || ID <= 999999 || ID >= 10000000) {
    System.out.println("Improper EMPID, please reenter your EMPID.\n");
    ID = Integer.parseInt(scan1.nextLine());
}

edited Aug 30 '18 at 17:58

answered Aug 30 '18 at 15:42

Jean-Serge Gagnon

9
2

Do-While loop user-entered not looping

3 Answers3