我有两个接口Bank和Account,它们有一些功能:
public interface Bank {
String createAccount(String owner) throws IOException;
boolean closeAccount(String number) throws IOException;
Set<String> getAccountNumbers() throws IOException;
Account getAccount(String number) throws IOException;
void transfer(Account a, Account b, double amount) throws IOException, IllegalArgumentException, OverdrawException, InactiveException;
}
public interface Account {
String getNumber() throws IOException;
String getOwner() throws IOException;
boolean isActive() throws IOException;
void deposit(double amount) throws IOException, IllegalArgumentException, InactiveException;
void withdraw(double amount) throws IOException, IllegalArgumentException, OverdrawException, InactiveException;
double getBalance() throws IOException;
}
我有一个类驱动程序,它有两个内部类Bank和Account来实现上面的接口,Bank有一个HashMap作为客户的帐户,一个客户可以有多个帐户具有不同的帐号。我无法解决的问题是,为每个客户生成这些帐号甚至多个! :
public class Driver {
private Bank bank = null;
static class Bank implements Bank {
private final Map<String, Account> accounts = new HashMap<>();
@Override
public Set<String> getAccountNumbers() {
return accounts.keySet();
}
@Override
public String createAccount(String owner) {
//TODO create new Account and return the account number
}
@Override
public boolean closeAccount(String number) {
//TODO if the account isActive and balance is zero then set it as inactive and return true.
return false;
}
@Override
public bank.Account getAccount(String number) {
return accounts.get(number);
}
@Override
public void transfer(bank.Account from, bank.Account to, double amount)
throws IOException, InactiveException, OverdrawException {
if (amount <= from.getBalance()) {
from.withdraw(amount);
to.deposit(amount);
}
}
static class Account implements Account {
private String number;
private String owner;
private double balance;
private boolean active = true;
Account(String owner) {
this.owner = owner;
//TODO set the account number ???
}
@Override
public double getBalance() {
return balance;
}
@Override
public String getOwner() {
return owner;
}
@Override
public String getNumber() {
return number;
}
@Override
public boolean isActive() {
return active;
}
@Override
public void deposit(double amount) throws InactiveException {
if (!isActive())
throw new InactiveException();
if (amount < 0)
throw new IllegalArgumentException();
balance += amount;
}
@Override
public void withdraw(double amount) throws InactiveException, OverdrawException {
if (!isActive())
throw new InactiveException();
if (amount > balance)
throw new OverdrawException();
if (amount < 0)
throw new IllegalArgumentException();
balance -= amount;
}
}
}
如何生成帐号? 有一个HashMap,所有现有帐户都存入银行。客户可以拥有多个帐号不同的帐户!它是如何工作的??
答案 0 :(得分:0)
您的Bank
课程可以在内部设置计数器来提供此功能。它将起作用,因为所有帐户仅由这一个银行对象维护,而不与其他帐户共享。
如果用户请求帐户,银行将向其提供计数器当前显示的编号,然后递增计数器。因此,下一个请求将获得不同的数字。
可能看起来像
public class Bank {
private int nextAccountId = 1;
public int createAccount(String owner) {
// Get account ID
int accountId = getUniqueAccountId();
// Create account
...
return accountID;
}
private int getUniqueAccountId() {
int accountId = nextAccountId;
// Increment ID for next request
nextAccountId++;
return accountId;
// Method can be made compact by just using
// return nextAccountId++;
}
}
显然这有一些缺点。它仅限于int
的范围(约4个Mrd帐户,当然可以使用long
进行扩展)。用户还可以查看该银行已拥有的帐户数量。并且很容易猜到其他用户帐户的有效ID。
对于更多随机方法,您可以使用
String uniqueID = UUID.randomUUID().toString();
有关详细信息,请参阅here。