[red_piscean]

user must enter the two numbers and its product and the program shud chek if its correct. it will prompt for the answer untill user hits 'quit' and then displays it.

class Product
{
    public static void main( String args[])throws IOException
     {

	 System.out.println(" This program checks the product of two numbers.");
	 System.out.println(" enter first number");

	 InputStreamReader I = new InputStreamReader(System.in);
	 BufferedReader br = new BufferedReader(I);

	 String s;
 	 s= br.readLine();
	 int a= Integer.parseInt(s);

	 System.out.println(" enter second number");
	 s= br.readLine();
 	 int b= Integer.parseInt(s);

	int res=a*b;

	System.out.println(" what is the product of " +a+ " and " +b+ "?");
	s= br.readLine();
	while(s!= "quit" || s!= "QUIT")
	{
	int p= Integer.parseInt(s);

	if(p==res)
	System.out.println(" Correct!");
	break;			

	else
	System.out.println(" NO! try again...");
	}
	
	System.out.println(" Product of " + a + " and " + b +" is " + res);
    }
}

the error is, i want my code to exit from the do loop after if is satisfied. and also, antering quit throws exceptions. cant understand.

[Renagado]

Why don't you copy paste the full exception text so we can explain it to you, plus without it we just have to guess

[red_piscean]

Renagado, on 14 May 2011 - 04:52 AM, said:

Why don't you copy paste the full exception text so we can explain it to you, plus without it we just have to guess

Exception in thread "main" java.lang.NumberFormatException: For input string: "q
uit"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at Product.main(Product.java:27)


nowww?????

[Renagado]

You're trying to cast a string to a number... that won't work. Also note that in your while loop you never read the input again.

	s= br.readLine();
	while(s!= "quit" || s!= "QUIT")
	{
	int p= Integer.parseInt(s);

	if(p==res)//you forgot brackets here
        {
	System.out.println(" Correct!");
	break;			
        }
	else
	System.out.println(" NO! try again...");

        s= br.readLine();//read input again, if its quit it will break out of the loop
	}//while loop ends here
	
	System.out.println(" Product of " + a + " and " + b +" is " + res);
    }
}

Note that this is still a bit dangerous, if you type something else then a integer or quit, you'll get the exception again. I'll leave it up to you to fix that if needed.

This post has been edited by Renagado: 14 May 2011 - 05:03 AM

[red_piscean]

it worked...i mean the logic. i replaced while with do while but m still getting the same exception when i enter quit! :'(

[Renagado]

Ok, post your new code then.

[red_piscean]

class Product
{
    public static void main( String args[])throws IOException
     {
	 String s;
	 System.out.println(" This program checks the product of two numbers.");
	
	 InputStreamReader I = new InputStreamReader(System.in);
	 BufferedReader br = new BufferedReader(I);

	 System.out.println(" enter first number");
 	 s= br.readLine();
	 int a= Integer.parseInt(s);

	 System.out.println(" enter second number");
	 s= br.readLine();
 	 int b= Integer.parseInt(s);

	int res=a*b;

	System.out.println(" what is the product of " +a+ " and " +b+ "?");
	s= br.readLine();
	
do{
	int p= Integer.parseInt(s);

	if(p==res)
	{System.out.println(" Correct!");
	break;}
	else
	System.out.println(" NO! try again...");
	s=br.readLine();
   }
	while(s!="quit");
	System.out.println(" product: "+res);
	
	 }
}

[Renagado]

A do loop will always run at least once. So if you enter quit it will try to convert that to a number again. That won't work.

[red_piscean]

the point is, how do i remove the number format exception??
evn if i replace it with a while loop, entering any string throws the exception.

[Renagado]

Am sorry, C# confusion got me again, you can't compare strings in Java using == or !=, you're only checking for object equality. This should work:

	s= br.readLine();
	while(!s.equals("quit") )
	{
	int p= Integer.parseInt(s);

	if(p==res)
        {
	System.out.println(" Correct!");
	break;
        }

	else
	System.out.println(" NO! try again...");
        s= br.readLine();
	}

This post has been edited by Renagado: 14 May 2011 - 05:37 AM

[pbl]

You can't compare STrings like that

s!="quit"

== and != compare if 2 Objects are the same not if they are equals
you will have to use the equals() method of the String class

(!s.equals("quit"))

[red_piscean]

O YES!!!!
THAT WORKS IN C LANGUAGE!


YIPPPEEEEEEEEEEEEEEEE!!!
THANKS!
IT WORKED!!!!

[Renagado]

Glad to see you're happy about it hehe
Anyway, you realise now what caused the error? I mean the string comparing, not the left out brackets etc.

[red_piscean]

yes! i realised it. c/c++ coding rules always interfere!
thanks a lot!!