Thread: Exception error display with one input and not the other

The following code is supposed to generate random numbers and give some output as long as the user wants to continue. But the problem is it gives an exception if I press 'y'. No problem occurs if I enter 'n'. Kindly check and tell what wrong I am doing:

import java.util.*; 
import static java.lang.System.out;
public class IsaacDice {
 
    public static void main(String[] args) {
 
    	out.println("Welcome to the dice game! Want to play?: Y/N");
    	Scanner reply=new Scanner(System.in);
    	char answer = reply.findInLine(".").charAt(0);
 
    	Random value=new Random();
    	while (answer=='y')
    	{
     		int randomNumber = value.nextInt(4) + 1;
switch (randomNumber) {
case 1:
out.println("Yes. Isn’t it obvious?");
break;
case 2:
out.println("No, and don’t ask again.");
break;
case 3:
out.print("Yessir, yessir!");
out.println(" Three bags full.");
break;
case 4:
out.print("What part of ‘no’");
out.println(" don’t you understand?");
break;
default:
out.print("You think you have");
out.print(" problems?");
out.print(" My random number");
out.println(" generator is broken!");
break;
}
out.println("Goodbye! Want to play again? y/n:");
out.println();
 
answer = reply.findInLine(".").charAt(0);
}
 
out.println("Exiting game!");
}
}

If I press 'n' the output is as desired:

Welcome to the dice game! Want to play?: Y/N
n
Exiting game!

Process completed.

However, if I enter 'y', the exception shows up:

Welcome to the dice game! Want to play?: Y/N
y
What part of ‘no’ don’t you understand?
Goodbye! Want to play again? y/n:

Exception in thread "main" java.lang.NullPointerException
at IsaacDice.main(IsaacDice.java:50)

Process completed.

hi the problem is solved here..
you were actually reading "." after y or n, but m sure you have never terminated your input with "."
because in the line char answer=reply.findInLine(".").charAt(0); means the reply will be the char at position 0, provided it should find "."

i have simplified your code
check this out

 
 
import java.util.*; 
import static java.lang.System.out;
public class IsaacDice {
 
    public static void main(String[] args) {
    	for(;;){
    	out.println("Welcome to the dice game! Want to play?: Y/N");
    	Scanner reply=new Scanner(System.in);
    	char answer = reply.findInLine("y|Y|n|N").charAt(0);
       	Random value=new Random();
 
    		if(answer=='y'||answer=='Y'){
     		int randomNumber = value.nextInt(4) + 1;
     		switch (randomNumber) {
     		case 1:
     			out.println("number is 1");
     			break;
     		case 2:
     			out.println("number is 2");
     			break;
     		case 3:
     			out.println("number is 3");
     			break;
     		case 4:
    			out.println(" number is 4");
     			break;
     		default:
     			out.print("You think you have");
     			out.print(" problems?");
     			out.print(" My random number");
     			out.println(" generator is broken!");
     			break;
     		}
     		out.println("Goodbye!");
     		out.println();
 
    		}
    		else{
 
    			out.print("BYE!!");
    			System.exit(0);
    		}
    	}
 
}
}

thank you for replying.
but what if I simply change "reply.findInLine(.).charAt(0)" to "reply.findInLine("y").charAt(0)" in my code (I want to do it the way I have done i.e., while loop)?
Shouldn't it remove this error? I still get the same exception, now with both inputs 'y' and 'n'.
Kindly explain me what exactly I should do. Sorry, I'm a beginner to java.