get accountNumber problem

[Nilla]

I have five classes: Account (abstract), SavingAccount, CreditAccount, GUI and Logic. My problem is the showSelecteAccountNumber method, and the problem is in this line: if(selectedAccountNr==konto.getAccountNumber()){

selectedAccountNr is no problem. It comes from the accountNrField. It is konto.getAccountNumber() which is the problem. Compilation is no problem but it gives the following error message

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at GUI.showSelectedAccount(GUI.java:556)
at GUI.access$16(GUI.java:546)
at GUI$ShowSelectedAccountListener.actionPerformed(GU I.java:173)

I think I don´t communicate correct between the classes, but I really don´t know how to get the accountNumber from the account list. Can someone help me to get it work??

Logic:

public class Logic{
	private ArrayList<Customer> customers = new ArrayList<Customer>();
        private ArrayList<Account> accounts = new ArrayList<Account>();
			
	public Logic()
	{
		customers = new ArrayList<Customer>();
		accounts = new ArrayList<Account>();
	}
	
	public void addCustomer(String fName, String eName, String pNumber){
		customers.add(new Customer(fName, eName, pNumber));
	}
	
	public void addSavingAccount(String pNumber) {
		accounts.add(new SavingAccounts(pNumber));
	}
		
	public void addCreditAccount(String pNumber) {
		accounts.add(new CreditAccounts(pNumber));
	}
	
	// Accessors
	
        public ArrayList<Customer> getAllCustomers(){
		return customers;
	}
	
	public ArrayList<Account> getAllAccounts(int acountNumber, double StartingBalance, String kontoTyp, String PNumber){
		return accounts;
	}
	
	public String getFirstNameForCustomerAt(int position){
		return (customers.get(position)).getFirstName();
	}
	
	public String getSecondNameForCustomerAt(int position){
		return (customers.get(position)).getSecondName();
	}
	
	public String getPNumberForCustomerAt(int position){
		return (customers.get(position)).getPNumber();
	}

        public int getAccountNumberForCustomerAt(int position){
		return (accounts.get(position)).getAccountNumber();
	}
		
	public ArrayList<Account> getAccounts() {
		return accounts;
	}

       .......
}

GUI:

public class GUI extends JFrame {
        private Customer kund;	
        private Logic logic;
	private Account konto;
	....	
	private JTextField firstNameField;
	private JTextField secondNameField;
	private JTextField pNumberField;
	private JTextField accountNrField;
	....	
	
        private ArrayList<Customer> customers;

        //JLists
        kunder=new JList(new DefaultListModel());
        konton = new JList<Object>();
	
        // Listerners
        // Menu
         ....
		
	private void addSAccount(int accountNumber, double balance, String kontoTyp, String valdKundPNr){
		logic.addSavingAccount(selectedKundPNr);
		konton.setListData(logic.getAllAccounts(accountNumber, startingBalance, kontoTyp, valdKundPNr).toArray());
		clear();
	}
	
	private void addCAccount(int accountNumber, double balance, String kontoTyp, String valdKundNr){
		logic.addCreditAccount(selectedKundPNr);
		konton.setListData(logic.getAllAccounts(accountNumber, startingBalance, kontoTyp, valdKundPNr).toArray());
		clear();
	}
	
	private int showSelectedAccount(String selectedCustomerNr){
		int position = kunder.getSelectedIndex();
		displayJTextArea.setText("");
		if(position > -1){
			firstNameField.setText(logic.getFirstNameForCustomerAt(position));
			secondNameField.setText(logic.getSecondNameForCustomerAt(position));
			selectedAccountNr= Integer.parseInt(accountNrField.getText());
			
				for(int j=0; j< konton.getModel().getSize(); j++){
						if(selectedAccountNr==konto.getAccountNumber()){
						Object item = konton.getModel().getElementAt(j);            
						displayJTextArea.append("\nKonto med " + item + " \n");
						}
				}
			}
		else {
			JOptionPane.showMessageDialog(null, "You have to select an account in the list!");
		}
		clear();
		return selectedAccountNr;
	}

[Norm]

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at GUI.showSelectedAccount(GUI.java:556)

Have you found the variable with the null value on line 556? You need to find which variable has the null value and then backtrack in the code to find out why that variable does not have a valid non-null value.

problem is in this line: if(selectedAccountNr==konto.getAccountNumber()){

Does the variable: konto have a valid value when line 556 is executed?

[Nilla]

I think the problem is private Account konto; in the Account class.
I don´t know how to get the right accountNumber from the arrayList accounts.

[Norm]

Does the variable: konto have a value when line 556 is executed?

Where is it assigned a value?

[ostkanten]

I think I have just solved the problem by changing
private ArrayList<Account> accounts;
to
List<Account> accounts = new ArrayList();
in the GUI class

Thanks for your interest in my problem.