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"main" java.lang.NullPointerException

8 replies on 1 page. Most recent reply: Jan 8, 2012 9:31 AM by leo kakios

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leo kakios

Posts: 5
Nickname: namadin
Registered: Jan, 2012

"main" java.lang.NullPointerException

Posted: Jan 6, 2012 12:00 PM

Hi am new here and also in java lang programming so i compile the code but there is an error which i cant see please help :P

import java.util.Scanner;

class NicePrice {

public static void main(String args[]) {
Scanner myScanner = new Scanner(System.in);
int age ;
double price = 0.00;
char reply ;
boolean isKid, isSenior, hasCoupon, hasNoCoupon;

System.out.print("How old are you ? ");
age = myScanner.nextInt();

System.out.print("Do you have a coupon(Y/N)");
reply = myScanner.findInLine(".").charAt(0);

isKid = age < 12;
isSenior = age >= 65;
hasCoupon = reply == 'Y' || reply == 'y' ;
hasNoCoupon = reply == 'N' || reply == 'n';

if (!isKid && !isSenior){
price = 9.25;
}
if (isKid || isSenior){
price = 5.25;
}
if (hasCoupon){
price -= 2.00;
}
if (!hasCoupon && !hasNoCoupon){
System.out.println("Ti?");
}

System.out.print("Please pay $");
System.out.print(price);
System.out.print(". ");
System.out.println("Geia Xara!");

}
}

With error {
How old are you ? 21
Do you have a coupon ? (Y/N) Exception in thread "main" java.lang.NullPointerException
at NicePrice.main(NicePrice.java:18)

Process completed.
}

Vincent O'Sullivan

Posts: 724
Nickname: vincent
Registered: Nov, 2002

Re: "main" java.lang.NullPointerException

Posted: Jan 6, 2012 1:34 PM

The line where the error occurs appears to have originally been two separate lines that have become joined together badly.

leo kakios

Posts: 5
Nickname: namadin
Registered: Jan, 2012

Re: "main" java.lang.NullPointerException

Posted: Jan 6, 2012 3:57 PM

:S didnt understand you there m8 please explain to me once more when u can ... thanks a lot

Vincent O'Sullivan

Posts: 724
Nickname: vincent
Registered: Nov, 2002

Re: "main" java.lang.NullPointerException

Posted: Jan 6, 2012 11:22 PM

OK. Let's start again. Did you write this code yourself?

leo kakios

Posts: 5
Nickname: namadin
Registered: Jan, 2012

Re: "main" java.lang.NullPointerException

Posted: Jan 7, 2012 2:02 AM

Goodmorning ;p.

No i didnt write it my self its a pratctise code in a book_for dummies_java_programming.pdf

Copied the code exactly how it was and it didnt run properly
made an other programm which uses "char " not only "int" and the problem was the same ....

George B

Posts: 24
Nickname: hmgeorge
Registered: Feb, 2008

Re: "main" java.lang.NullPointerException

Posted: Jan 7, 2012 7:36 AM

I tried running this and it ran fine for me.

The only way I could reproduce the problem was to hit ctrl-d after the second prompt. If I gave it valid input it worked fine:


  $ java NicePrice
  How old are you ? 21
  Do you have a coupon(Y/N)y
  Please pay $7.25. Geia Xara!
  $

I'm running on a Linux box. My guess is that maybe it has problems running under Windows? Maybe the <cr><lf> line termination is giving it trouble?

leo kakios

Posts: 5
Nickname: namadin
Registered: Jan, 2012

Re: "main" java.lang.NullPointerException

Posted: Jan 7, 2012 10:01 AM

A fast debug brought me here before this line

System.out.print("Do you have a coupon ? (Y/N) ");
reply = myScanner.findInLine(".").charAt(0); <=== this line has error

Debug jumped me here at Thread.java in this line

private void dispatchUncaughtException(Throwable e) {
getUncaughtExceptionHandler().uncaughtException(this, e);
}

i have downloaded the java api doc etc from an old link ... dunno m8 if my win7 have the problem am not pro on this stuff plz whenever you have time send me a quick link for java doc .zip /.rar i might have problem in the doc files :/

THANKS A LOT
cant find them googled them everywere

Vincent O'Sullivan

Posts: 724
Nickname: vincent
Registered: Nov, 2002

Re: "main" java.lang.NullPointerException

Posted: Jan 8, 2012 5:19 AM

Ah, OK. The example program is bad in very many ways (even if you exclude the fact that it doesn't work).

The simplest way to get this code to work is to replace

.findInLine(".")

with

.next()

(The code gives the same error both in Windows and Mac. The error is down to the author not using the Scanner object properly to process keyboard input.)

leo kakios

Posts: 5
Nickname: namadin
Registered: Jan, 2012

Re: "main" java.lang.NullPointerException

Posted: Jan 8, 2012 9:31 AM

Omg it worked.... i can finaly continue ouf...

A Big BIG THANKS.... finaly i was thinking that api had problems etc :P a big relief :P

Thanks a lot again. +1

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