Trouble using || OR operator (Java)

Morpork

Hi, just started learning Java and I've ran into a snag.

The first code works exactly as I want it to.
(EasyIn. is just replacing the scanner function)

class single
{
	public static void main(String[] args)
	{

		char ans;

		do
		{
			System.out.print("Enter a");

			ans = EasyIn.getChar();

			while (ans != 'a')  
			{
				System.out.println("Please enter a");
				ans = EasyIn.getChar();
			}

		 }while (ans == 'a');  

	}
}

This however, doesn't work. It just keeps asking to enter a or b even if I enter them first time or anytime.

class multiple
{
	public static void main(String[] args)
	{

		char ans;

		do
		{
			System.out.print("Enter a");

			ans = EasyIn.getChar();

			while ((ans != 'a') || (ans != 'b'))
			{
				System.out.println("Please enter a");
				ans = EasyIn.getChar();
			}

		 }while ((ans == 'a') || (ans == 'b'));

	}
}

Can't figure it out! Can someone please help?
Thanks.

Edit: solved, thank you!

Basq

Not sure why you'd need an inner while..

public static void main(String[] args)
{
	char ans;

	do
	{
		System.out.print("Please Enter a");
		ans = EasyIn.getChar();
	} while ((ans != 'a') || (ans != 'b'));
}

Would something like that not be sufficient?

Not fully sure what you're trying to achieve - you're asking for a yet accepting b?

Boskowski

if either the left side of the expression is true OR the right is true the entire expression becomes true, thats what OR does, hence you stay in the loop.
so regardless whether you enter 'a' or 'b' or anything for that matter the expression becomes TRUE and its rinse and repeat, right?
unless you invent an new character that is 'a' and 'b' at the same time.

Morpork

Thanks for the replies.

I get what you're saying Boskowski. I wasn't aware of that.
Sorry for not explaining it well Basq.

Basically I'm trying to get the user to enter 'Y' or 'y' or 'N' or 'n' as a choice to run the program again or not. And if the users enters anything but those characters it asks to enter one of those characters.

So I should use the && operator in conjunction with the || operator?
Maybe I'm over complicating things.

Also, sorry I forgot to add the "or b" in the second code.

Morpork

Yes this works perfectly!

class multiple
{
	public static void main(String[] args)
	{

		char ans;

		do
		{
			System.out.print("Enter a or b");

			ans = EasyIn.getChar();

			while ((ans != 'a') && (ans != 'b'))
			{
				System.out.println("Please enter a or b");
				ans = EasyIn.getChar();
			}

		 }while ((ans == 'a') || (ans == 'b')); 

	}
}

Boskowski

sorry my java is not quite fluent but the essence should be correct:

class multiple {
public static void main(String[] args) {
   do {
      // do stuff HERE that you may want repeated or not

      System.out.print("Repeat? (Y/N)");
      char ans = '';

      do { 
         ans = EasyIn.getChar();
      } while ( ans != 'Y' && ans != 'N' )
// alternatively      } while NOT ( ans == 'Y' || ans == 'N' )

   } while ( ans == 'Y' ); 
}

Morpork

Interesting! I'll play around with that. Thank you.