if-else loop within a do while loop within another do while loop

Question

When 'y' or 'Y' is inputted, I want the code to the prompt System.out.print("Y/y or N/n: "); starting from the first do,but instead the code will prompt System.out.print("bad answer, try again: ");, and I only want char besides y,Y,n,N to be the case.

The only code that follows is when 'n' or 'N' is entered, following System.exit(0);

import java.util.Scanner;
public class Test
{
   public static void main(String[] args)
   {
      Scanner kb = new Scanner(System.in);
      char ch;
      do
      {
         System.out.print("Y/y or N/n: ");
         do
         {
            ch = kb.nextLine().charAt(0);
            if (ch == 'n' || ch == 'N')
            {
               System.exit(0);
            }
            else if (ch != 'y' || ch != 'Y' || ch != 'n' || ch != 'N');
            {
               System.out.print("bad answer, try again: ");
            }

         }
         while (ch != 'y' || ch != 'Y' || ch != 'n' || ch != 'N');
      }   
      while (ch == 'y' || ch == 'Y');
   }
}

You should use && instead of ||.

Maroun
– Maroun

2014-11-17 17:41:01 +00:00
Commented Nov 17, 2014 at 17:41 — Maroun
– Maroun, Commented Nov 17, 2014 at 17:41

Andy Thomas · Accepted Answer · 2014-11-25 13:04:24Z

2

Because you're using OR rather than AND, this condition will always be true:

else if (ch != 'y' || ch != 'Y' || ch != 'n' || ch != 'N')
{
    System.out.print("bad answer, try again: ");
}

By the way, you could simplify this to have a single do-while. If the answer is bad, just go on to the next iteration of the outer loop.

edited Nov 25, 2014 at 13:04

answered Nov 17, 2014 at 17:40

Andy Thomas

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Comments

kriyeta · Accepted Answer · 2014-11-17 17:59:13Z

1

Remove semicolon and check for ch and take AND. Code could be like this:

else if (ch != 'y' && ch != 'Y' && ch != 'n' && ch != 'N')
{
       System.out.print("bad answer, try again: ");
}

OR

Remove semicolon and check for ch and take OR and finally take NOT. Code could be like this:

 else if (!(ch == 'y' || ch == 'Y' || ch == 'n' || ch == 'N'))
 {
       System.out.print("bad answer, try again: ");
  }

edited Nov 17, 2014 at 17:59

answered Nov 17, 2014 at 17:50

kriyeta

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3 Comments

Andy Thomas Over a year ago

+1 - I missed that semicolon! Might be worthwhile to explain to the OP what that semicolon causes to happen.

kriyeta Over a year ago

@AndyThomas the statement after 'if' runs no matter if the expression is true or not. because ; acts as a null statement after 'if' Thats why 'if' statement completes after ; and statements next to ; doesn't depend on if conditon.

Andy Thomas Over a year ago

In addition, the { System.out.println(...) } is legal because Java allows a sequence of statements and declarations to be enclosed in braces, as a block. (BTW, the semicolon is technically an "empty statement.")

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