Loop problem
Can some kind person help me with this loop?
The user needs to input a number between 5 and 15. It needs to loop until they enter a correct number.
The error is noted in the code.
Thanks,
publicclass Five{
publicstaticvoid main( String[ ] args ){
int choice = 0;
String input;//error: local variable input is never read
while (choice >= 5 || choice <= 15);
{
input = JOptionPane.showInputDialog("Enter number between 5 and 15");
if (choice >= 5 && choice <= 15)
// correct response
JOptionPane.showMessageDialog(null,"You got it right!" );
{
// incorrect response
JOptionPane.showMessageDialog(null,"Nice try! Attempt was incorrect...Try again" );
}
}
}
}
[1450 byte] By [
Fedjea] at [2007-10-3 8:29:31]
Draw a number line.
Use it to indicate >= 5. (greater than or equal to 5)
Now indicate <= 15. (less than or equal to 15)
|| evaluates to true if at least one of its operands is true. So as long as a number is on at least one of those parts of the number line you indicated, your while condition will be true.
Can you tell me a number that is both NOT >= 5 AND ALSO NOT <= 15? This is the kind of number you need for the while to be false.
In addition, you have this:
while (...) ; { /* stuff */ }
That's the same as
while (...) { /* nothing */ } { /* stuff */ }
Get rid of the semicolon after the while condition.
First of all, you have a semi-colon after your while. Look at this:
String input = JOptionPane.showInputDialog("Enter number between 5 and 15");
int choice = Integer.parseInt(input);
while(choice > 15 || choice < 5)
{
//redo
}
The error means exactly what it says: You assign a value to input, but you never use it. Presumably you want to parse input into choice.
> String input;//error: local variable input is
> s never read
That's not an error. It's just a warning. Your code will still compile. It's legal, but the compiler has noticed that something's fishy. Like the error message says--you're never using that variable. There's no point to have a variable if you never use its value.
> cross posted.It was? Where?
I think he meant my code on the cross post comment. I never put the question anywhere else.
I removed the semi colon after the while statement. Your right it does compile, but never ends because any number I put in will give the 'try again' return, which says it's wrong, even if it's not!
Dang I'm getting a headache!
if (choice >= 5 && choice <= 15)// correct responseJOptionPane.showMessageDialog(null, "You got it right!" );Look at your logic here.
You really dont even need an if-statement inside your while loop. Read a String before the loop, and keep looping until a correct response is entered, then show the correct response message dialog after the loop.
This makes the most sense after I get the whole statement through my dyslexic brain. I'll have to break it down into parts...
"Read a String before the loop"
String input;
input = JOptionPane.showInputDialog("Enter number between 5 and 15");
"keep looping until a correct response is entered"
while (choice >= 5 && choice <= 15)
"then show the correct response message dialog after the loop"
JOptionPane.showMessageDialog
Then do this again for the incorrect answer? Nope, tried that while I was writing this. I get the answer is correct when it's not.
I'm tired and know this should be simple! Probably in wrong order or some dumb thing.
Here is where I'm at now...
import javax.swing.*;// provides JOptionPane class
public class Five{
public static void main( String[ ] args ) {
int choice = 0;
String input;
input = JOptionPane.showInputDialog("Enter number between 5 and 15");
// correct response
JOptionPane.showMessageDialog(null, "You got it right!" );
while (choice >= 5 && choice <= 15)
{
// incorrect response
JOptionPane.showMessageDialog(null, "Nice try! Attempt was incorrect...Try again" );
while (choice < 5 && choice > 15);
}
}
}
while (choice >= 5 && choice <= 15)You do not want your loop to be like this. That would be a correct answer. You want it to loop if choice is less than 5 or if choice is greater than 15.
Yes I did see that after I posted. Changed it to this... while (choice < 5 && choice > 15) and tried this.... while(choice<5 || choice >15) still gives them as all correct answers!Message was edited by: Fedje
So you have something like this:
String input;
input = JOptionPane.showInputDialog("Enter number between 5 and 15");
int choice = Integer.parseInt(input);
while(choice < 5 || choice > 15)
{
//incorrect response
//redo
}
//correct response
And its not working?
> Yes I did see that after I posted. Changed it to
> this... while (choice < 5 && choice > 15)
This will be true for every number that is both less than 5 and greater than 15. Can you name a number that's less than 5 and greater than 15?
If you're dyslexic, you really should try some other means to help you visualize the meaning of the string of tokens. For example, what you have above could be like this:
< 5 <|
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
>15|>
&& means any number that meets both of those conditions--that is, falls on both of those lines. No number matches that, so the while condition can never be true;
For your initial x >= 5 || x <= 15, you have this:
>= 5|>
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
<= 15<|
|| means at least one of those conditions is met, so the while condition is true for any number that's on at least one of those lines. Every number is on at least one of them, so it's always true.
> this.... while(choice<5 || choice >15) still gives
> them as all correct answers!
That sounds fishy. I'd have to see more code.
while (choice < 5 || choice > 15) {
// tell them the choice is wrong, must bet between 5 and 15, inclusive
}
< 5<--|
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
> 15|-->
|| means keep doing the "you got it wrong" part as long as the number is on at least one of those lines. So "you got it wrong" is everything except the blank space between 5 and 15.
I also see two while loops in your most recent code. That doesn't make sense.
jverda at 2007-7-21 12:28:08 >
> I never put the question anywhere else.Funny, you seem to have the exact same syntax problems with if statements and while loops as a Ms. Linda Guy. Same class name as well.
7studa at 2007-7-21 12:28:08 >
> > I never put the question anywhere else.> > Funny, you seem to have the exact same syntax> problems with if statements and while loops as a Ms.> Linda Guy. Same class name as well.Link?
jverda at 2007-7-21 12:28:08 >
Sorry about the lapse in this, I had a computer problem.
This helps to understand a lot! Thanks!
I decided to try this as an "if/else" It almost works, but still gives the wrong answer, they're reversed! If I put in 3 it says right, put in 7 and it says wrong. I tried switching the output, still the same.
import javax.swing.*;// provides JOptionPane class
public class FivetoFifteen {
public static void main(String[] args) {
String input;
input = JOptionPane.showInputDialog("Enter number between 5 and 15");
int choice = Integer.parseInt(input);
if (choice <= 5 || choice >= 15){
// correct response
JOptionPane.showMessageDialog(null, "You got it right!" );
} else {
// incorrect response
JOptionPane.showMessageDialog(null, "Nice try! Attempt was incorrect...Try again" );
}
}
}
Fedjea at 2007-7-21 12:28:08 >
if (choice <= 5 || choice >= 15)Your logic is wrong here. The answer is right if choice is greater than 5 and less than 15.
This is the only thread I have started on this forum, am I registered twice and making two threads? If so, I'm sorry.
I had tried another forum with no answers to questions or help given, and came here.
I have to say I have had better results on this thread! I understand a lot better what I'm doing, and why!
The chart with the lines helped a lot, and I will use that in the future. My final problem is why it is reversed, sounds like my dyslexia at work, but I tried reversing things in case that was the problem with the same results.
Fedjea at 2007-7-21 12:28:08 >
Original Message:
Re: Loop problem
CaptainMorgan08 Registered: May 10, 2006 8:31 AM Oct 29, 2006 9:55 AM
if (choice <= 5 || choice >= 15)
Your logic is wrong here. The answer is right if choice is greater than 5 and less than 15.
I tried changing it toif (choice >=5 || choice <=15) and get the same result.
Correction: It says 'correct' for both that way.
Message was edited by:
Fedje
Fedjea at 2007-7-21 12:28:08 >
> I tried changing it toif (choice >=5 || choice<=15) and get the same result.Thats says "if choice is greater than 5 or less than 15." This is always true. Change the 'or' to an 'and.'
Okay, I changed the output statements around and now all are 'not correct.' It seems my 'else' statement is not working, did I do it right? I followed the tutorial, and show no errors.
Fedjea at 2007-7-21 12:28:08 >
Keep the outputs like the were when you last posted your code. Just change the if statement to "if choice is greater than 5 and choice is less than 15."
I finally got it!!!!!! Dang dysleyxia! Yippie!! Yippie!! Yippie!!
I see I have to draw a chart for things like this.
Two of you really helped me a lot, can I add more Duke Dollars and divide them between you? ;>)
Yes, I see I could do this and they have been awarded! Thanks!
Message was edited by:
Fedje
Fedjea at 2007-7-21 12:28:08 >
>I had tried another forum with no answers to questions or help givenAnother lie.
7studa at 2007-7-21 12:28:08 >
AH HA!! Your the one told to be nice on the other site! Personally I couldn't understand WHAT you were trying to tell me to do.
If you read through this thread you will see how to help a noobie. After all, we're very stupid until we learn. I really envy your knowledge, but until I learn this...that is all I can do is envy you.
Fedjea at 2007-7-21 12:28:08 >
CaptainMorgan08...You would be proud of me!
I changed this to a while loop so it will repeat until they put in a correct number.
It only repeats once right now, then closes, but I will find how to make it do what I want!
Probably just needs some little piece of code to do it.
import javax.swing.*;// provides JOptionPane class
public class Five{
public static void main( String[ ] args ) {
String input;
String wrong;
input = JOptionPane.showInputDialog("Enter number between 5 and 15");
int choice = Integer.parseInt(input);
while (choice >= 5 && choice <= 15)
// correct response
JOptionPane.showMessageDialog(null, "You got it right!");
{
// incorrect response
wrong = "";
JOptionPane.showMessageDialog(null, "Nice try! Attempt was incorrect...Try again");
JOptionPane.showInputDialog("Enter number between 5 and 15");
}
}
}
Fedjea at 2007-7-21 12:28:08 >
I don't like handing over code, but you've obviously been working on this and struggling with it, so here you go.
choice = ...;
while (choice < 5 || choice > 15) { // keep going until they enter a number between 5 and 15
error message "number has to be between 5 and 15
input = ...;
choice = ...;
}
// once we get here, they have finally entered a number between 5 and 15.
The way you're doing it now (in reply 29), you're going to continue asking for input as long as they're entering numbers between 5 and 15. I thought that what you wanted is to require a number between 5 and 15, and so you'd need to keep asking for input as long as they're entering numbers outside that range.
jverda at 2007-7-21 12:28:13 >
FYI, here's a summary.
// #1 keep going until they enter a number between 5 and 15.
// That is, keep going as long as the number is outside that range.
while (choice < 5 || choice > 15)
// #2 keep going until they enter a number NOT between 5 and 15.
// That is, keep going as long as the number is inside the range.
// The exact opposite of #1.
while (choice >=5 && choice <= 15)
// #3 keep going until they enter a number that is both
// less than 5 and greater than 15
// This will never be true, since no single number is both < 5 and > 15
while (choice < 5 && choice > 15)
// #4 keep going until they enter a number that is either
// greater than or equal to 5 OR less than or equal to 15.
// This will loop forevever, because every number satisfies
// at least one of those conditions.
// The exact opposite of #3.
while (choice >= 5 || choice <= 15)
jverda at 2007-7-21 12:28:13 >
>If you read through this thread you will see how >to help a noobie. I try to avoid helping cross posters.
7studa at 2007-7-21 12:28:13 >
