java.lang.NullPointerException

[stevenhaynes5]

Hi,

Im new to java and im just messing around with a few things. Ive put thew following code togther but i get a java.lang.NullPointerException.

package questionaireadvanced;
import java.util.Scanner;

public class QuestionaireAdvanced {

    public static void main(String[] args) {
        
        Scanner myScanner = new Scanner(System.in);
        
        String[] questions = new String[2];
        questions[0] = "Whats is my name";
        questions[1] = "What is my age";
        
        char[] answer = new char[2];
        
        for (int i = 0; i < questions.length; i++) {
            System.out.println(questions[i]);
            answer[i] = myScanner.findInLine(".").charAt(0);
            
            switch (answer[i]) {
                case 'a':
                    System.out.println("Wrong!");
                    break;
                case 'b':
                    System.out.println("Well done!");
                    break;
                case 'c':
                    System.out.println("Wrong!");
                    break;
                case 'd':
                    System.out.println("Wrong!");
                    break;
                default:
                    System.out.println("You did not enter a, b, c, or d");
                    break;
            }
        }
        
        System.out.println("The program is now exiting");
    }
}

Any help would be very much appriciated.

[Toll]

Could we get a stacktrace of the exception (i.e. what is output to the console)? It makes it much easier pinpointing the error.

[stevenhaynes5]

Hi Toll,

Here is the output

run:
Whats is my name
b
Well done!
What is my age
Exception in thread "main" java.lang.NullPointerException
	at questionaireadvanced.QuestionaireAdvanced.main(QuestionaireAdvanced.java:18)
Java Result: 1
BUILD SUCCESSFUL (total time: 2 seconds)

Thanks

[Toll]

It seems to indicate that the problem is in "answer[i] = myScanner.findInLine(".").charAt(0);". After reading the docs for Scanner (I must admit, I've never really used Scanner), I'm starting to believe that the problem stems from it not finding the pattern in the line. Does the program stop before you enter the second answer, or after?

[stevenhaynes5]

The second question is printed on the screen but ends when it want to take input. Here is another run.

run:
Whats is my name
a
Wrong!
Exception in thread "main" java.lang.NullPointerException
What is my age
	at questionaireadvanced.QuestionaireAdvanced.main(QuestionaireAdvanced.java:18)
Java Result: 1
BUILD SUCCESSFUL (total time: 2 seconds)

[Toll]

Then I'm rather certain that the findInLine() method doesn't actually advance lines, but just looks in the last entered line. So it's trying to find the next character in the line with your first answer, and since it can't find any more characters, it returns null according to its specifications. Try finding another method to use; have a look at Scanner (Java Platform SE 6) to see if you can find one that suits you.

[stevenhaynes5]

After thinking about what you said i ran the program again with entering two charcters. The program ran without any errors.

run:
Whats is my name
ab
Wrong!
What is my age
Well done!
The program is now exiting
BUILD SUCCESSFUL (total time: 2 seconds)

I had a look through the scanner documentation you provided and i carnt see a methord that suits my needs in there.

COuld you recommend somthing else?

[Toll]

Well... The nextline-method looks nice to me.