Java 具有多态性的银行应用程序，getter 变为空

Question

我完全迷失了，我无法恢复或克服这个问题。

我想要做的是拥有一个银行应用程序，我应该在其中拥有应该从帐户 class 继承的 SavingsAccount 和 CreditAccount。当我的 subclasses 尝试 getBalance/getIntereset 时，我没有得到正确的值，而是有时得到 Null。

你能帮我指出问题并看看需要解决什么问题才能使我的 withdraw() 和 deleteCustomer() 方法正常工作吗？

非常感谢！

逻辑class


import java.text.NumberFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;

public class BankLogic {

        //Deklarera global lista med kunder
    private ArrayList<Customer> customers = new ArrayList<>();
    private ArrayList<Transaction> transactions = new ArrayList<>();
    Date date;

    public ArrayList<String> getAllCustomers() {
        ArrayList<String> customersStr = new ArrayList<>();
        if (customers == null) {
            customersStr.add("");
            return customersStr;
        } else
            for (Customer customer : customers) {
                customersStr.add(customer.getpNo() + " " + customer.getName() + " " + customer.getSurname());
            }
        return customersStr;
    }

  
    public boolean createCustomer(String name, String surname, String pNo) {
        try {
            for (int i = 0; i < customers.size(); i++) {
                if (customers.get(i).getpNo().equals(pNo)) {
                    return false;
                }
            }
            if (!name.equals("") || !surname.equals("")) {
                Customer customer = new Customer(name, surname, pNo);
                customers.add(customer);
                return true;
            }
        } catch (Exception e) {
            System.out.println(e);
        }
        return false;
    }


   
    public ArrayList<String> getCustomer(String pNo) {
        ArrayList<String> presentCustomerArr = new ArrayList<>();

        try {
            for (int i = 0; i < customers.size(); i++) {
                if (customers.get(i).getpNo().equals(pNo)) {
                    presentCustomerArr.add(customers.get(i).getpNo() + " " + customers.get(i).getName() + " " + customers.get(i).getSurname());
                    ArrayList<Account> accountList = customers.get(i).getCustomerAccounts();
                    if (customers.get(i).getCustomerAccounts() != null) {
                        for (int j = 0; j < accountList.size(); j++) {
                            presentCustomerArr.add(accountList.get(j).getAccountNumber() + " " + stringFormatted(accountList.get(j).getBalance()) + " " + accountList.get(j).getAccountType() + " " + accountList.get(j).getInterestRate() + " %");
                        }
                    }
                    return presentCustomerArr;
                }
            }
        } catch (Exception e) {
            System.out.println(e);
        }
        return null;
    }

   
    public boolean changeCustomerName(String name, String surname, String pNo) {

        for (int i = 0; i < customers.size(); i++) {
            if (customers.get(i).getpNo().equals(pNo)) {
                if (!name.equals("") && !surname.equals("")) {
                    customers.get(i).setName(name);
                    customers.get(i).setSurname(surname);
                    return true;
                }
                if (name.equals("") && !surname.equals("")) {
                    customers.get(i).setName(customers.get(i).getName());
                    customers.get(i).setSurname(surname);
                    return true;
                }
                if (!name.equals("") && surname.equals("")) {
                    customers.get(i).setName(name);
                    customers.get(i).setSurname(customers.get(i).getSurname());
                    return true;
                }
            }
        }

        return false;
    }

    
    public int createSavingsAccount(String pNo) {

        try {
            for (int i = 0; i < customers.size(); i++) {
                if (customers.get(i).getpNo().equals(pNo)) {
                    ArrayList<Account> accountList = new ArrayList<>();

                    if (customers.get(i).getCustomerAccounts() != null) {
                        accountList = customers.get(i).getCustomerAccounts();
                    }
                    SavingsAccount savingsAccount = new SavingsAccount();
                    accountList.add(savingsAccount);
                    customers.get(i).setCustomerAccounts(accountList);
                    int accNr = -1;
                    for (int j = 0; j < accountList.size(); j++) {
                        accNr = savingsAccount.getAccountNumber();
                    }
                    return accNr;
                }
            }

        } catch (Exception e) {

        }

        return -1;
    }

    
    public String getAccount(String pNo, int accountId) {

        for (int i = 0; i < customers.size(); i++) {
            if (customers.get(i).getpNo().equals(pNo)) {

                if (customers.get(i).getCustomerAccounts() != null) {
                    ArrayList<Account> accountList = customers.get(i).getCustomerAccounts();
                    for (int j = 0; j < accountList.size(); j++) {
                        if (accountList.get(j).getAccountNumber() == accountId) {
                            String accPresentation = accountList.get(j).getAccountNumber() + " " + stringFormatted(accountList.get(j).getBalance()) + " " + accountList.get(j).getAccountType() + " " + accountList.get(j).getInterestRate() + " %";
                            return accPresentation;
                        }
                    }
                }
            }

        }
        return null;
    }

    
    public boolean deposit(String pNo, int accountId, int amount) {
        if (amount > 0) {
            for (int i = 0; i < customers.size(); i++) {
                if (customers.get(i).getpNo().equals(pNo)) {
                    if (customers.get(i).getCustomerAccounts() != null || customers.get(i).getCustomerAccounts() != null) {
                        ArrayList<Account> accountList = customers.get(i).getCustomerAccounts();
                        for (int j = 0; j < accountList.size(); j++) {
                            if (accountList.get(j).getAccountNumber() == accountId) {
                                accountList.get(j).setBalance(Double.valueOf(accountList.get(j).getBalance() + amount));
                                transactions = addTransaction(new Date(), amount, accountList.get(j).getBalance(), accountList.get(j).getAccountNumber(), false);
                                customers.get(j).setAccountTransactions(transactions);
                                return true;
                            }
                        }
                    }
                }

            }
        }
        return false;
    }

    
    private ArrayList<Transaction> addTransaction(Date date, int amount, Double balance, int accountnumber, boolean isAWithdrawal) {
        Transaction transaction = new Transaction(new Date(), (double) amount, balance, accountnumber, isAWithdrawal);
        transactions.add(transaction);

        return transactions;
    }

    
    public boolean withdraw(String pNo, int accountId, int amount) {

        Boolean isUpdated = false;
        if (amount > 0) {

            for (int i = 0; i < customers.size(); i++) {
                if (customers.get(i).getpNo().equals(pNo)) {
                    if (customers.get(i).getCustomerAccounts() != null) {
                        ArrayList<Account> accountList = customers.get(i).getCustomerAccounts();
                        for (int j = 0; j < accountList.size(); j++) {

                            if (accountList.get(j).getAccountNumber() == accountId) {
                                isUpdated = accountList.get(j).withdraw(accountList, amount, customers, transactions);
                                if (isUpdated){
                                    return false;
                                }

                                //transactions = accountList.get(j).addTransaction(transactions, date, amount, Double.valueOf(accountList.get(j).getBalance()), accountList.get(j).getAccountNumber(), true);
                                customers.get(j).setAccountTransactions(transactions);
                                return true;

                            }
                        }
                    }
                }

            }
        }
        return false;
    }

    public void updateTransactions(ArrayList<Transaction> transactions) {
        this.transactions = transactions;
    }

    
    private boolean balanceAfterWithdrawIsOk(int amount, Double balance) {
        if (balance - amount < -5000) {
            return false;
        } else return true;
    }

    
    public String closeAccount(String pNr, int accountId) {
        for (int i = 0; i < customers.size(); i++) {
            if (customers.get(i).getpNo().equals(pNr)) {
                if (customers.get(i).getCustomerAccounts() != null) {
                    ArrayList<Account> accountList = customers.get(i).getCustomerAccounts();
                    for (int j = 0; j < accountList.size(); j++) {
                        if (accountList.get(j).getAccountNumber() == accountId) {
                            String closedAcc = accountList.get(j).calculateClosedAccountBalance(customers.get(i).getCustomerAccounts().get(j));
                            customers.get(i).getCustomerAccounts().remove(accountList.get(j));
                            return closedAcc;
                        }
                    }
                }
            }

        }
        return null;
    }

    
    public ArrayList<String> deleteCustomer(String pNo) {

        ArrayList<String> deletedCustomerArr = new ArrayList<>();

        try {
            for (int i = 0; i < customers.size(); i++) {
                if (customers.get(i).getpNo().equals(pNo)) {
                    int accNr = -1;
                    deletedCustomerArr.add(customers.get(i).getpNo() + " " + customers.get(i).getName() + " " + customers.get(i).getSurname());

                    ArrayList<Account> accountList = customers.get(i).getCustomerAccounts();
                    if (customers.get(i).getCustomerAccounts() != null) {
                        for (int j = 0; j < accountList.size(); j++) {

                            //String hej = stringFormatted(accountList.get(j).getInterest());
                            try {
                            String addString = accountList.get(j).getAccountNumber() + " " + stringFormatted(accountList.get(j).getBalance()) + " " + accountList.get(j).getAccountType() + " " + stringFormatted(accountList.get(j).getInterest());
                            deletedCustomerArr.add(addString);

                            }
                            catch (Exception e) {
                                System.out.println(e);
                            }

                        }
                        accountList.clear();
                    }
                    customers.remove(i);
                    return deletedCustomerArr;
                }

            }
        } catch (Exception e) {
            System.out.println(e);
        }


        return null;
    }

    
    public int createCreditAccount(String pNo) {

        try {
            for (int i = 0; i < customers.size(); i++) {
                if (customers.get(i).getpNo().equals(pNo)) {
                    ArrayList<Account> accountList = new ArrayList<>();
                    if (customers.get(i).getCustomerAccounts() != null) {
                        accountList = customers.get(i).getCustomerAccounts();
                    }
                    for (int j = 0; j < accountList.size(); j++) {
                    }
                    CreditAccount creditAccount = new CreditAccount((double) 0, 0.5, "Kreditkonto");
                    accountList.add(creditAccount);
                    customers.get(i).setCustomerAccounts(accountList);
                    int accNr = -1;
                    for (int j = 0; j < accountList.size(); j++) {
                        accNr = creditAccount.getAccountNumber();
                    }
                    return accNr;
                }
            }

        } catch (Exception e) {
        }

        return -1;
    }

    
    public ArrayList<String> getTransactions(String pNo, int accountId) {
        ArrayList<String> arrList = new ArrayList<>();
        try {
            for (Customer customer : customers) {
                if (customer.getpNo() == pNo) {
                    for (Transaction transaction : customer.getAccountTransactions()) {
                        if (accountId == transaction.getAccountNumber()) {
                            transactions.get(this.transactions.indexOf(transaction));
                            arrList.add(simpleDateFormatter(transactions.get(this.transactions.indexOf(transaction)).getDateAndTime()) + " " + (transactions.get(this.transactions.indexOf(transaction)).isAWithdrawal() == true ? "−" : "").concat(stringFormatted(transactions.get(this.transactions.indexOf(transaction)).getAmount())) + " Saldo: " + stringFormatted(transactions.get(this.transactions.indexOf(transaction)).getBalanceAfterTransaction()));
                        }


                    }
                }
            }
        } catch (NullPointerException e) {
            for (Customer customer : customers) {
                for (int i = 0; i < customer.getCustomerAccounts().size(); i++) {
                    if (customer.getCustomerAccounts().get(i).getAccountNumber() == accountId && customer.getAccountTransactions() == null) {
                        return arrList;
                    }
                }
                if (customer.getAccountTransactions() == null) {
                    return null;
                }
            }
            return null;
        }
        return arrList;
    }

    // Custom methods

    
    private String stringFormatted(Double balance) {
        balance = Double.valueOf(balance);
        String balanceStr = NumberFormat.getCurrencyInstance().format(balance);
        return balanceStr;
    }

    
    private String simpleDateFormatter(Date date) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String strDate = sdf.format(date);
        return strDate;
    }

}

帐号class


import java.util.ArrayList;
import java.util.Date;

public abstract class Account {

 

    private Double balance;
    private Double interestRate;
    private Double interest;
    private int accountNumber;
    private String accountType;
    private int numberOfWithdraws = 0;
    private static int lastAssignedNumber = 1000;

    public Account() {
        lastAssignedNumber++;
        this.balance = Double.valueOf(0);
        this.accountNumber = lastAssignedNumber;
    }

    public Account(Double balance, Double interestRate, String accountType, int lastAssignedNumber) {
    }

    public Account(Double balance, Double interestRate, String accountType) {
        lastAssignedNumber++;
        this.accountNumber = lastAssignedNumber;
        this.balance = balance;
        this.interestRate = interestRate;
        this.accountType = accountType;
    }

    public Account(Double balance, Double interestRate, Double interest, int accountNumber, String accountType, int numberOfWithdraws) {
        this.balance = balance;
        this.interestRate = interestRate;
        this.interest = interest;
        this.accountNumber = accountNumber;
        this.accountType = accountType;
        this.numberOfWithdraws = numberOfWithdraws;
    }

    public Double getBalance() {

        return balance;
    }

    public void setBalance(Double balance) {
        this.balance = balance;
    }

    public Double getInterestRate() {
        return interestRate;
    }

    public void setInterestRate(Double interestRate) {
        this.interestRate = interestRate;
    }

    public Double getInterest() {

        return interest;
    }

    public int getAccountNumber() {
        return accountNumber;
    }

    public String getAccountType() {
        return accountType;
    }

    public void setAccountType(String accountType) {
        this.accountType = accountType;
    }

    public int getNumberOfWithdraws() {
        return numberOfWithdraws;
    }

    public void setNumberOfWithdraws(int numberOfWithdraws) {
        this.numberOfWithdraws = numberOfWithdraws;
    }

    /
    public abstract String calculateClosedAccountBalance(Account customerAccounts);

    
    public ArrayList<Transaction> addTransaction(ArrayList<Transaction> transactions, Date date, int amount, Double balance, int accountnumber, boolean isAWithdrawal) {
        Transaction transaction = new Transaction(new Date(), (double) amount, balance, accountnumber, isAWithdrawal);
        transactions.add(transaction);

        return transactions;
    }

    public abstract boolean withdraw(ArrayList<Account> customerAccounts, int amount, ArrayList<Customer> customers, ArrayList<Transaction> transactions);

    public abstract String stringFormatted(Double balance);
}

信用账户


import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Date;

public class CreditAccount extends Account {

    

    private String accountType = "Kreditkonto";
    private Double interestRate;
    private Double creditLimit = Double.valueOf(5000);
    private Double interest;
    private Double balance;


    public CreditAccount(String accountType, Double interestRate, Double creditLimit) {
        this.accountType = accountType;
        this.interestRate = interestRate;
        this.creditLimit = creditLimit;
    }

    public CreditAccount(Double balance, Double interestRate, String accountType, int lastAssignedNumber, String accountType1, Double interestRate1, Double creditLimit) {
        super(balance, interestRate, accountType, lastAssignedNumber);
        this.accountType = accountType1;
        this.interestRate = interestRate1;
        this.creditLimit = creditLimit;
    }

    public CreditAccount(Double balance, Double interestRate, String accountType, String accountType1, Double interestRate1, Double creditLimit) {
        super(balance, interestRate, accountType);
        this.accountType = accountType1;
        this.interestRate = interestRate1;
        this.creditLimit = creditLimit;
    }

    public CreditAccount(Double balance, Double interestRate, String accountType) {
        super(balance, interestRate, accountType);

    }

    public CreditAccount(Double balance, Double interestRate, Double interest, int accountNumber, String accountType, int numberOfWithdraws) {
        super(balance, interestRate, interest, accountNumber, accountType, numberOfWithdraws);
    }

    public CreditAccount() {
    }

    public CreditAccount(Double balance, Double interestRate, String accountType, int lastAssignedNumber) {
        super(balance, interestRate, accountType, lastAssignedNumber);
    }

    public Double getCreditLimit() {
        return creditLimit;
    }

    
    @Override
    public String calculateClosedAccountBalance(Account customerAccounts) {
        String closedAccStr = "";

        closedAccStr = customerAccounts.getAccountNumber() + " " + stringFormatted(customerAccounts.getBalance()) + " " + customerAccounts.getAccountType() + " " + stringFormatted(customerAccounts.getInterest());


        return closedAccStr;
    }

    @Override
    public String stringFormatted(Double balance) {
        String balanceStr = NumberFormat.getCurrencyInstance().format(balance);
        return balanceStr;
    }

    @Override
    public String getAccountType() {
        return accountType;
    }

    @Override
    public Double getInterestRate() {
        if (this.getBalance() < 0) {
            this.interestRate = Double.valueOf(7);
        } else this.interestRate = Double.valueOf(0.5);
        return interestRate;
    }
    @Override
    public Double getInterest() {

        if (getBalance() < 0) {
            interest = getBalance() * -7 / 100;
        }

        return interest;
    }

    @Override
    public boolean withdraw(ArrayList<Account> accountList, int amount, ArrayList<Customer> customers, ArrayList<Transaction> transactions) {
        for (int j = 0; j < accountList.size(); j++) {
            if (accountList.get(j).getAccountType().equals("Kreditkonto")) {
                if (balanceAfterWithdrawIsOk(amount, accountList.get(j).getBalance())) {
                    accountList.get(j).setBalance(Double.valueOf(accountList.get(j).getBalance() + (-amount)));
                    if (accountList.get(j).getBalance() < 0) {
                        accountList.get(j).setInterestRate(Double.valueOf(7));
                    }
                    transactions = addTransaction(transactions, new Date(), amount, Double.valueOf(accountList.get(j).getBalance()), accountList.get(j).getAccountNumber(), true);
                    BankLogic bankLogic = new BankLogic();
                    bankLogic.updateTransactions(transactions);
                    customers.get(j).setAccountTransactions(transactions);
                    return true;
                }
            }
        }
        return false;
    }

    
    private boolean balanceAfterWithdrawIsOk(int amount, Double balance) {
        if (balance - amount < -5000) {
            return false;
        } else return true;
    }

}

储蓄账户


import java.text.NumberFormat;
import java.util.ArrayList;

public class SavingsAccount extends Account {


    private String accountType = "Sparkonto";
    private Double interestRate = 1.2;
    private Double withdrawalFeePercentage = Double.valueOf(2);
    private Double interest;


    public SavingsAccount(String accountType, Double interestRate, Double withdrawalFeePercentage) {
        this.accountType = accountType;
        this.interestRate = interestRate;
        this.withdrawalFeePercentage = withdrawalFeePercentage;
    }

    public SavingsAccount(Double balance, Double interestRate, String accountType, int lastAssignedNumber, String accountType1, Double interestRate1, Double withdrawalFeePercentage) {
        super(balance, interestRate, accountType, lastAssignedNumber);
        this.accountType = accountType1;
        this.interestRate = interestRate1;
        this.withdrawalFeePercentage = withdrawalFeePercentage;
    }

    public SavingsAccount(Double balance, Double interestRate, String accountType, String accountType1, Double interestRate1, Double withdrawalFeePercentage) {
        super(balance, interestRate, accountType);
        this.accountType = accountType1;
        this.interestRate = interestRate1;
        this.withdrawalFeePercentage = withdrawalFeePercentage;
    }

    public SavingsAccount(Double balance, Double interestRate, String accountType, int accountNumber, int numberOfWithdraws, double withdrawalFeePercentage) {
        super(balance, interestRate, accountType, accountNumber);
        this.withdrawalFeePercentage = Double.valueOf(2);
    }

    public SavingsAccount() {

    }

    
    @Override
    public String calculateClosedAccountBalance(Account customerAccounts) {
        String closedAccStr = "";

            closedAccStr = customerAccounts.getAccountNumber() + " " + stringFormatted(customerAccounts.getBalance()) + " " + customerAccounts.getAccountType() + " " + stringFormatted(customerAccounts.getInterest());


        return closedAccStr;
    }

    @Override
    public String stringFormatted(Double balance) {
        String balanceStr = NumberFormat.getCurrencyInstance().format(balance);
        return balanceStr;
    }

    public Double getWithdrawalFeePercentage() {
        return withdrawalFeePercentage;
    }

    @Override
    public String getAccountType() {
        return accountType;
    }

    @Override
    public Double getInterestRate() {
        return interestRate;
    }

    @Override
    public Double getInterest() {
        interest = getBalance() * 1.2 / 100;
        return interest;
    }

    @Override
    public boolean withdraw(ArrayList<Account> accountList, int amount, ArrayList<Customer> customers, ArrayList<Transaction> transactions) {
        for (int j = 0; j < accountList.size(); j++) {
            if (accountList.get(j).getAccountType().equals("Sparkonto")) {
                //accountList.get(j).withdrawMoney();
                if (accountList.get(j).getNumberOfWithdraws() > 0) {
                    amount = (int) (amount * 1.02);
                }
                if (accountList.get(j).getBalance() >= amount) {
                    accountList.get(j).setBalance(Double.valueOf(accountList.get(j).getBalance() - amount));
                    accountList.get(j).setNumberOfWithdraws(+1);
                    BankLogic bankLogic = new BankLogic();
                    bankLogic.updateTransactions(transactions);
                    return true;
                }
            }
        }
        return false;
    }
}

Answer 1

如果您在 getBalance/getInterest 时得到空值，您一定还没有初始化它们。我建议跟踪您的代码并使用 debugger/print 语句来查找您何时 assign/update 这些值，因为您的继承结构似乎是正确的。

Java 具有多态性的银行应用程序，getter 变为空

Java banking app with polymorphism, getter getting null

java

object

oop

polymorphism

getter-setter