Getting Null Pointer Exception in runtime

Please can sum1 help me with the above error in this code:

Code :

import java.util.*; //required for List and ArrayList
import java.io.*; //required for IOException
 
public class TextFileTester
{
public static void main(String[] args)
	{
	char choice;
	//create an object of type list to store the cars in
	List<Car> carList = new ArrayList<Car>();
	//read the list from file when program starts
	readList(carList);
 
		//menu options
		do
			{
			System.out.println("\nText File Tester");
			System.out.println("1. Add a car");
			System.out.println("2. Remove a car");
			System.out.println("3. List all cars");
			System.out.println("4. Quit\n");
			choice = KBInput.readChar();
			System.out.println();
 
			switch(choice)
				{
				case '1': addCar(carList);break;
				case '2': removeCar(carList);break;
				case '3': listAll(carList);break;
				case '4': writeList(carList);break;
				default: System.out.println("Choose an option between 1-4");
				}
			}
		while(choice != '4');
	}
 
//method for adding a new car to the system
private static void addCar(List<Car> carListIn)
	{
	String tempReg;
	String tempMake;
	double tempPrice;
 
	System.out.println("Enter the veichle reg");
	tempReg = KBInput.readString();
	System.out.println("Enter the veichle make");
	tempMake = KBInput.readString();
	System.out.println("Enter veichle price");
	tempPrice = KBInput.readDouble();
 
	carListIn.add(new Car(tempReg, tempMake, tempPrice));
	}
 
//method for removing a car from the list
private static void removeCar(List<Car> carListIn)
	{
	int pos;
	System.out.println("Enter the position of the car to be removed");
	pos = KBInput.readInt();
	carListIn.remove(pos -1);
	}
 
 
//method for show all the cars in the list
private static void listAll(List<Car> carListIn)
	{
		for(Car item: carListIn)
		{
			System.out.println(item.getRegistration() + ""
			+ item.getMake() + "" + item.getPrice());
		}
	}
 
//method for writing car list to file
private static void writeList(List<Car> carListIn)
	{
	try
		{
		//create a file writer
		FileWriter carFile = new FileWriter("Car.txt");
		//create a print writer
		PrintWriter carWriter = new PrintWriter(carFile);
		for(Car item: carListIn)
			{
			carWriter.println(item.getRegistration());
			carWriter.println(item.getMake());
			carWriter.println(item.getPrice());
			}
		carWriter.close();
		}
 
		//handle the exceptions thrown up by the file writer
			catch(IOException e)	
				{
				System.out.println("There was a problem writing the file");
				}
	}
 
//method for reading the car file
private static void readList(List<Car> carListIn)
	{
	String tempReg;
	String tempMake;
	String tempStringPrice;
	double tempPrice;
 
		try
			{
			//create a file reader
			FileReader carFile = new FileReader("Car.txt");
			//create a buffer for reader
			BufferedReader carStream = new BufferedReader(carFile);
			tempReg = carStream.readLine();
			while (tempReg != null);
				{
				tempMake = carStream.readLine();
				tempStringPrice = carStream.readLine();
				// converting price from text to double
				tempPrice = Double.parseDouble(tempStringPrice);
				carListIn.add
								(new Car(tempReg, tempMake, tempPrice));
								tempReg = carStream.readLine();
				}
				carStream.close();
 
			}
			catch (FileNotFoundException e)
				{
				System.out.println("File could not be found");
				}
 
			catch (IOException e)
				{
				System.out.println("There was a problem reading the file");
				}
	}
}

The error:

----jGRASP exec: java TextFileTester

Exception in thread "main" java.lang.NullPointerException
at sun.misc.FloatingDecimal.readJavaFormatString(Floa tingDecimal.java:991)
at java.lang.Double.parseDouble(Double.java:510)
at TextFileTester.readList(TextFileTester.java:119)
at TextFileTester.main(TextFileTester.java:12)

----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.

from another forum i believe the variable tempStringPrice has a null value but i'm not sure what to set it to. Any help would be much appreciated :)