null pointer exception

[anthonym2121]

When I run it and make a deposit or withdrawal I get a null pointer exception. I was wondering how I could fix this??? Thanks

import javax.swing.JOptionPane;

public class A5Q1ummadhoa{
     public static void main(String[] arguments){
       
       String[] accountNumber = new String[100];
       Double[] accountBalance = new Double[100];
       String[] firstName = new String[100];
       String[] lastName = new String[100];
       Double[] creditLimit = new Double[100];
       String[] choices = {"Create Account","Deposit","Withdraw","Quit"};
       String accountNum = "";
       int numAccounts = 0;
       double result;
       Boolean done = false;
       Boolean isValid = false;

       for(int i=0;i<1000 && !done;i++){
       String input = (String)JOptionPane.showInputDialog(null,"Select an option:","Main Menu",JOptionPane.QUESTION_MESSAGE,null,choices,choices[0]);
            System.out.println("* You selected: " + input);
            if(input.equals(choices[0])){
              createNewCustomer(accountNumber[i],accountBalance[i],firstName[i],lastName[i],creditLimit[i]);
              //accountNumber[numAccounts];
              numAccounts++;
              accountBalance[i]=0.00;
              creditLimit[i]=100.00;
            }
            if(input.equals(choices[1])){
              accountNum = JOptionPane.showInputDialog("What is your account number?");
              getAccountIndex(accountNum, accountNumber);
              result = makeDeposit(accountNumber[i],accountBalance[i], creditLimit[i]);
              accountBalance[i]+=result;
                creditLimit[i]=accountBalance[i]*0.10;
            }
            if(input.equals(choices[2])){
              accountNum = JOptionPane.showInputDialog("What is your account number?");
              getAccountIndex(accountNum, accountNumber);
              result = makeWithdrawal(accountNumber[i],accountBalance[i], creditLimit[i]);
              accountBalance[i]-=result;
                creditLimit[i]=accountBalance[i]*0.10;
              
            }
            if(input.equals(choices[3])){
              printAllAccounts(accountNumber,accountBalance,firstName,lastName,creditLimit);
              done = true;
            }
       }
       System.out.println();
       System.out.println("The program terminated normally.");
     }
     
     public static String createNewCustomer(String accountNumber,Double accountBalance,String firstName,String lastName,Double creditLimit){
       String result = "";
       
       final String BANK_ID = "A4326";
       firstName = JOptionPane.showInputDialog("Please enter your first name:");
       lastName = JOptionPane.showInputDialog("Please enter your last name:");
       accountNumber = generateAccountNumber(firstName, lastName);
       accountBalance = 0.00;
       creditLimit = 100.00;
       
       printAccount(accountNumber,accountBalance,firstName,lastName,creditLimit);
       
       return result;
     }
     
     public static void printAccount(String accountNumber,Double accountBalance,String firstName,String lastName,Double creditLimit){
       
       System.out.println(lastName + ", " + firstName);
       System.out.println("Account Number: " + accountNumber);
       System.out.println("Account Balance: " + "$" + roundDouble(accountBalance,2));
       System.out.println("Credit Limit: " + "$" + roundDouble(creditLimit,2));
       
     }
     
     public static void printAllAccounts(String[] accountNumber,Double[] accountBalance,String[] firstName,String[] lastName,Double[] creditLimit){
       
       System.out.println("*** Summary of Accounts ***" + "\nBank ID: A4326");
       System.out.println();
       System.out.println(lastName + ", " + firstName);
       System.out.println(accountNumber);
       System.out.println(accountBalance);
       System.out.println(creditLimit);
       
       
     }
     
     public static double makeDeposit(String accountNumber,Double accountBalance,Double creditLimit){
       Double result = 0.00;
       String deposit = "";
         
       deposit = JOptionPane.showInputDialog("How much money would you like to deposit? (e.g. ##.##)");
       result = Double.parseDouble(deposit);
         
         return result;
     }
     
     public static double makeWithdrawal(String accountNumber,Double accountBalance,Double creditLimit){
       Double result = 0.00;
       String withdraw = "";
         
       withdraw = JOptionPane.showInputDialog("How much money would you like to withdraw? (e.g. ##.##)");
       result = Double.parseDouble(withdraw);
       
         return result;
     }
     
     public static int getAccountIndex(String accountNum, String accountNumber[]){
       int result = -1;
       
       for(int i=0;i<accountNumber.length;i++){
        
         if(accountNum.equals(accountNumber[i])){
          result = i; 
         }
       }
       return result;
     }
     
     
     
     public static String generateAccountNumber(String firstName, String lastName){
    String bankId = "A4326";
      String result = "";
      final String BANK_ID = "A4326";
      int[]randNums4 = new int[1000];
      int[]randNums8 = new int[1000];
      int i;
      
      for(i = 0;i<randNums4.length-1;i++){
       randNums4[i] = (int)(9000.0*Math.random()+1000);
      }
      
      for(i = 0;i<randNums8.length-1;i++){
        randNums8[i] = (int)(90000000.0*Math.random()+10000000);
      }
       result += BANK_ID+"-"+lastName.charAt(0)+firstName.charAt(0)+"-"+randNums4[i-1]+"-"+Character.toUpperCase(lastName.charAt(1))+Character.toUpperCase(firstName.charAt(1))+"-"+randNums8[i-1];

     return result;  
     }
     
     public static final double roundDouble(double d, int places) {
        return Math.round(d * Math.pow(10, (double) places)) / Math.pow(10,
            (double) places);
    }
}

[Fubarable]

what line throws the NPE?

The more information you can give about the problem, usually the easier it is to help you.

[Singing Boyo]

you're forgetting to set the array values.
when you declare your arrays you also need a for loop to set the values

you set them using this

       String[] accountNumber = new String[100];
       Double[] accountBalance = new Double[100];
       String[] firstName = new String[100];
       String[] lastName = new String[100];
       Double[] creditLimit = new Double[100];
       String[] choices = {"Create Account","Deposit","Withdraw","Quit"};
       String accountNum = "";
       int numAccounts = 0;
       double result;
       Boolean done = false;
       Boolean isValid = false;

what you really want is this

String[] accountNumber = new String[100];
       Double[] accountBalance = new Double[100];
       String[] firstName = new String[100];
       String[] lastName = new String[100];
       Double[] creditLimit = new Double[100];
       String[] choices = {"Create Account","Deposit","Withdraw","Quit"};
       String accountNum = "";
       int numAccounts = 0;
       double result;
       Boolean done = false;
       Boolean isValid = false;
       
       for(int i=0; i<100; i++){
              accountBalance[i] = new Double(0);
              firstName[i] = "";
              lastName[i] = "";
              creditLimit[i] = new Double(0);
       }

As it was explained to me, creating arrays using something like Double[] a = new Double[100] simply allocates memory. To use the array, you need to set the values as well.

Hope this helps,
Singing Boyo

[Singing Boyo]

And next time, do indicate the line throwing the exception. I had to copy the code into my IDE and compile it to find the line.(a very tedious process, as my CPU is very slow right now)

[Fubarable]

Actually, the real problem is that you are using array of Double which is a wrapper class for the double primitive. Don't do this. Instead if you use arrays of double (note that it's not capitalized), your code should work fine.

I would use a text editor to search out every occurrence of Double and change it to double.

[anthonym2121]

what line throws the NPE?

The more information you can give about the problem, usually the easier it is to help you.

accountBalance[i]+=result;

[anthonym2121]

you're forgetting to set the array values.
when you declare your arrays you also need a for loop to set the values

you set them using this

       String[] accountNumber = new String[100];
       Double[] accountBalance = new Double[100];
       String[] firstName = new String[100];
       String[] lastName = new String[100];
       Double[] creditLimit = new Double[100];
       String[] choices = {"Create Account","Deposit","Withdraw","Quit"};
       String accountNum = "";
       int numAccounts = 0;
       double result;
       Boolean done = false;
       Boolean isValid = false;

what you really want is this

String[] accountNumber = new String[100];
       Double[] accountBalance = new Double[100];
       String[] firstName = new String[100];
       String[] lastName = new String[100];
       Double[] creditLimit = new Double[100];
       String[] choices = {"Create Account","Deposit","Withdraw","Quit"};
       String accountNum = "";
       int numAccounts = 0;
       double result;
       Boolean done = false;
       Boolean isValid = false;
       
       for(int i=0; i<100; i++){
              accountBalance[i] = new Double(0);
              firstName[i] = "";
              lastName[i] = "";
              creditLimit[i] = new Double(0);
       }

As it was explained to me, creating arrays using something like Double[] a = new Double[100] simply allocates memory. To use the array, you need to set the values as well.

Hope this helps,
Singing Boyo

this seems to work and I don't have the NPE error. The problem is that it is not recording the account number into the array. When I want it to print accountNumber[i] it prints nothing!

[Webuser]

Paste the thrown error text here.