java - 抛出自己的异常

问题描述

我有这个班级帐户

    import java.io.IllegalArgumentException;

    class Account {
        final int accountNo;
        final Customer owner;
        final double overdraft;

        double balance = 0;

        private Account(int accountNo, Customer owner, double overdraft) {
            this.accountNo = accountNo;
            this.owner = owner;
            this.overdraft = overdraft;
        }

        void print() {
            Out.println("Kontonummer: " + accountNo);
            owner.print();
            Out.format("Kontostand: %.2f%nÜberziehungsrahmen: %.2f%n", balance, overdraft);
        }

        public boolean deposit(double amount) throws IllegalArgumentException {
            if (amount <= 0) {
                throws new IllegalArgumentException("Cannot deposit negative amounts!");
                break;
            } else {
                balance += amount;
                return true;
            }

            public boolean withdraw(double amount) throws OverdraftLimitReachedException {
                if (amount <= 0 || !isCovered(amount)) {
                    throw new OverdraftLimitReachedException("Overdraft limit has been reached", accountNo);
                    break;
                } else {
                    balance -= amount;
                    return true;
                }

                boolean isCovered(double amount) {
                    return amount - overdraft <= balance;
                }

                boolean transfer(Account target, double amount) {
                    boolean success = withdraw(amount);
                    if (!success) return false;

                    target.deposit(amount);
                    return true;
                }
            }
        }
    }

现在我也有我写的这个例外

    public class NoSuchAccountException extends AccountException {

        public NoSuchAccountException(int accountNo) {
            super(message, accountNo);
        }
    }

现在我需要在类帐户中抛出这个异常，当搜索到的帐号不存在时。现在我的问题是在哪个方法（或函数我认为是相同的，如果我错了请纠正我）我应该抛出这个异常。经过什么检查。我将如何检查帐号是否存在，如果不存在，我会抛出这个异常。谢谢！

编辑：班级银行业务，以完成该计划

class Banking {
  static final int CAPACITY = 100;

  final Account[] accounts = new Account[CAPACITY];
  int nOfAccounts = 0;

  int createAccount(String firstName, String lastName, String phone, double overdraft) {
    if (nOfAccounts == CAPACITY) return -1;

    // use nOfAccounts as accountNo and index to array
    Customer owner = new Customer(firstName, lastName, phone);
    Account account = new Account(nOfAccounts, owner, overdraft);
    accounts[nOfAccounts] = account;
    nOfAccounts++;

    return account.accountNo;
  }

  boolean deposit(int accountNo, double amount) {
    if (accountNo < 0 || accountNo >= nOfAccounts) return false;

    Account account = accounts[accountNo];
    return account.deposit(amount);
  }

  boolean withdraw(int accountNo, double amount) {
    if (accountNo < 0 || accountNo >= nOfAccounts) return false;

    Account account = accounts[accountNo];
    return account.withdraw(amount);
  }

  boolean transfer(int fromNo, int toNo, double amount) {
    if (fromNo < 0 || toNo < 0 ||
        fromNo >= nOfAccounts || toNo >= nOfAccounts) return false;

    Account from = accounts[fromNo];
    Account to = accounts[toNo];
    return from.transfer(to, amount);
  }

  double getBalance(int accountNo) {
    if (accountNo < 0 || accountNo >= nOfAccounts) return 0;

    Account account = accounts[accountNo];
    return account.balance;
  }

  double getBalance() {
    double sum = 0;

    for (int i = 0; i < nOfAccounts; i++) {
      sum += accounts[i].balance;
    }
    return sum;
  }

  void print() {
    Out.println("---------- Bankauszug ----------");

    for (int i = 0; i < nOfAccounts; i++) {
      accounts[i].print();
      Out.println("--------------------------------");
    }
    Out.format("Bilanzsumme: %.2f%n", getBalance());
    Out.println("--------------------------------");
  }

  // --------------------- Optionaler Teil ---------------------

  public static void main(String[] args) {
    Banking banking = new Banking();
    char op;

    do {
      printMenu();
      op = readOperation();

      switch (op) {
        case 'a': {
          printTitle("Konto anlegen");
          String firstName = getString("Vorname");
          String lastName = getString("Nachname");
          String phone = getString("Telefonnummer");
          double overdraft = getDouble("Überziehungsrahmen");

          int accountNo = banking.createAccount(
            firstName, lastName, phone, overdraft);
          printMessage("Anlegen von Konto " + accountNo, accountNo != -1);
          break;
        }
        case 'e': {
          printTitle("Einzahlen");
          int accountNo = getInt("Kontonummer");
          double amount = getDouble("Einzahlungsbetrag");

          boolean success = banking.deposit(accountNo, amount);
          printMessage("Einzahlen", success);
          break;
        }
        case 'b': {
          printTitle("Abheben");
          int accountNo = getInt("Kontonummer");
          double amount = getDouble("Abhebungsbetrag");

          boolean success = banking.withdraw(accountNo, amount);
          printMessage("Abheben", success);
          break;
        }
        case 't': {
          printTitle("Überweisen");
          int fromNo = getInt("Von Kontonummer");
          int toNo = getInt("Auf Kontonummer");
          double amount = getDouble("Betrag");

          boolean success = banking.transfer(fromNo, toNo, amount);
          printMessage("Überweisen", success);
          break;
        }
        case 'd':
          banking.print();
          break;
        case 'q':
          Out.println("Beenden");
          break;
        default:
          Out.println("Ungültige Operation");
          break;
      }
    } while(op != 'q');
  }

  static void printMenu() {
    Out.println();
    Out.println("*********** Bankverwaltung ********");
    Out.println("Konto anlegen ................... a");
    Out.println("Einzahlen ....................... e");
    Out.println("Beheben ......................... b");
    Out.println("Überweisen ...................... t");
    Out.println("Übersicht drucken ............... d");
    Out.println("Beenden ......................... q");
    Out.print("Welche Menuoption? [a|e|b|t|d|q]: ");
  }

  static char readOperation() {
    char ch = Character.toLowerCase(In.readChar());
    In.readLine();
    return ch;
  }

  static void printTitle(String text) {
    Out.println("*** " + text + " ***");
  }

  static String getString(String text) {
    Out.print(text + ": ");
    return In.readLine();
  }

  static double getDouble(String text) {
    Out.print(text + ": ");
    return In.readDouble();
  }

  static int getInt(String text) {
    Out.print(text + ": ");
    return In.readInt();
  }

  static void printMessage(String operation, boolean success) {
    String message = success ?
      operation + " erfolgreich durchgeführt" :
      "Ungültige Operation";
    Out.println(message);
  }
}

标签： javaexceptionerror-handling

这取决于您创建的界面。您当前的代码中有一个接口，如果找不到帐户或其他失败，您将在该接口中返回 false。这种错误处理有利有弊。一种可能很脆弱的方法是方法的调用者可能忘记检查返回码，这对于这种情况可能非常糟糕（调用者首先尝试提取一些钱，但失败了，然后存钱到另一个帐户，凭空创造资金）。

有赞成也有反对。进行错误处理的另一种方法是抛出异常而不是返回布尔值进行错误处理 - 这将有其自身的优点和缺点。在 Java 中，如果您确保它是已检查异常，则调用者将被迫捕获或抛出异常作为类型系统的一部分。无论如何，我不知道混合这两种处理错误的方式是什么感觉，因为这可能非常容易出错和令人困惑。

如果您采用异常处理错误的方式，一种常见的重构可能是使用名为的私有方法checkOrThrowAccountMustExist，该方法将帐户 ID 作为输入，如果不存在则抛出。

还有一个问题是是否将支票放在Banking班级和/或Account班级中。我自己的感觉是，在两者中至少包含一些检查可能是有意义的，并且最好在那些暴露在外部或程序其他部分的类中包含检查（并记录一个类不打算在程序的一小部分之外使用）。但这可能会或可能不会超出您的任务范围。

java - 抛出自己的异常

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