*Note: I have pointers to all created objects. read is initialized in the constructor of the code, as is write. So I'm still confused as to why the exception is occurring. First off, I apologize in advance for the potentially dirty and unrefined coding which is going to follow. I'm not making a career out of this, nor am I studying computer science. I'm trying to make a (relatively) simple program to keep track of some statistics. Everything else works, but when I try to write the gathered stats to a text file, I get a nullpointerexception, at the first read.nextLine() in the readFile() function. The idea is to first read the values already present in the file, add those to the values gathered during the program session, then rewrite the combined values into the file. Below is the complete file:
`import java.util.Scanner; import java.io.*;
public class StatTracker {
private static int numCustomers = 0, BOGO = 0, PERC = 0, BDAY = 0;
private static final String[] couponTypes = {"BOGO","PERC","BDAY"};
private static boolean run = true;
private static final Scanner input = new Scanner(System.in);
private static final String fileName = "Statistics.txt";
private static PrintWriter write;
private static Scanner read;
public StatTracker() throws IOException, FileNotFoundException{
Scanner read = new Scanner(fileName);
PrintWriter write = new PrintWriter(fileName);
} //End constructor
public static void main(String[] args) throws IOException {
StatTracker stat = new StatTracker();
stat.program(run);
} //End main
public static void program(boolean r) throws IOException{
while (r){
getInfo();
System.out.println("Continue? (y/n): ");
cont(input.next());
} //End while
} //End program
public static int[] readFile() throws FileNotFoundException{
int custTemp = 0, BOGOtemp = 0, PERCtemp = 0, BDAYtemp = 0;
read.nextLine();
custTemp = read.nextInt();
read.nextLine();
BOGOtemp = read.nextInt();
read.nextLine();
PERCtemp = read.nextInt();
read.nextLine();
BDAYtemp = read.nextInt();
read.close();
int[] currentValues = {custTemp,BOGOtemp,PERCtemp,BDAYtemp};
return currentValues;
} //End readFile
public static void writeToFile(int[] vals) throws IOException{
int custTemp = getNumCustomers() + vals[0], BOGOtemp = getBOGO() + vals[1], PERCtemp = getPERC() + vals[2], BDAYtemp = getBDAY() + vals[3];
write.println("Customers:");
write.println(custTemp);
write.println("Buy One Get One Discounts Used:");
write.println(BOGOtemp);
write.println("Percent Off Discounts Used:");
write.println(PERCtemp);
write.println("Birthday Discounts Used:");
write.println(BDAYtemp);
write.close();
} //End writeToFile
//Checks whether to continue running the program
public static void cont(String answer) throws IOException, FileNotFoundException {
int[] temp = new int[4];
if (answer.equals("y")) {
System.out.println("Program still running. Current totals:");
System.out.println("Customers: " + getNumCustomers());
System.out.println("BOGO coupons used: " + getBOGO());
System.out.println("Percent off coupons used: " + getPERC());
System.out.println("Birthday coupons used: " + getBDAY());
} else if (answer.equals("n")){
System.out.println("Writing statistics to file.");
temp = readFile();
writeToFile(temp);
System.out.println("Closing program.");
switchRun();
} //End if
} //End cont
public static int getBOGO(){
return BOGO;
} //End getBOGO
public static int getPERC(){
return PERC;
} //End getBOGO
public static int getBDAY(){
return BDAY;
} //End getBOGO
public static int getNumCustomers(){
return numCustomers;
} //End getNumCustomers
public static void switchRun(){
if (getRun()){
run = false;
} else {
run = true;
} //End if
} //End switchRun
public static boolean getRun(){
return run;
} //End getRun
public static String getCouponType(int index){
return couponTypes[index];
} //End getCouponType
public static void getInfo(){
int temp = 0, BOGOtemp = 0, PERCtemp = 0, BDAYtemp = 0;
boolean checkTemp = false;
System.out.println("Enter the number of customers:");
temp = input.nextInt();
addToNumCustomers(temp);
while (true){
System.out.println("If any coupons were used, please enter the number of each in this order:");
System.out.println(getCouponType(0)+ ", " + getCouponType(1) + ", " + getCouponType(2));
BOGOtemp = input.nextInt();
PERCtemp = input.nextInt();
BDAYtemp = input.nextInt();
if (checkTooMany(BOGOtemp,PERCtemp,BDAYtemp,temp)){
System.out.println("More coupons than customers. Please re-enter.");
} else {
addToCoupons("BOGO", BOGOtemp);
addToCoupons("PERC", BOGOtemp);
addToCoupons("BDAY", BOGOtemp);
break;
}//End if
}
} //End getInfo
public static boolean checkTooMany(int b, int p, int bd, int c){
//Checks to make sure there aren't more coupons than people.
if((b + p + bd) > c) {
return true;
} else {
return false;
} //End if
} //End check
public static void addToNumCustomers(int num){
numCustomers += num;
} //End addNumCustomers
public static void addBOGO(int num){
while(true){
if(num >= 0){
BOGO += num;
break;
} else {
System.out.println("Invalid number, please re-enter.");
num = input.nextInt();
}//End if
} //End while
} //End addBOGO
public static void addPERC(int num){
while(true){
if(num >= 0){
PERC += num;
break;
} else {
System.out.println("Invalid number, please re-enter.");
num = input.nextInt();
}//End if
} //End while
} //End addPERC
public static void addBDAY(int num){
while(true){
if(num >= 0){
BDAY += num;
break;
} else {
System.out.println("Invalid number, please re-enter.");
num = input.nextInt();
} //End if
} //End while
} //End addBDAY
public static void addToCoupons(String type,int num){
while(true){
if (type.equalsIgnoreCase(getCouponType(0))){
addBOGO(num);
break;
} else if (type.equalsIgnoreCase(getCouponType(1))){
addPERC(num);
break;
} else if (type.equalsIgnoreCase(getCouponType(2))){
addBDAY(num);
break;
} else {
System.out.println("Invalid coupon type, please re-enter.");
type = input.nextLine();
} //End if
} //End while
} //End addToCoupons
} //End StatTracker`
I have tried creating a new file from the program itself (with File new file), creating an empty .txt file, creating one with garbage data on each necessary line, and creating one with a space on each line. Any help you can provide would be greatly appreciated.
