设计模式实战：银行账户管理系统的设计与实现
// 账户抽象类
abstract class Account {
private double balance;
private List<Observer> observers = new ArrayList<>();
public Account(double initialBalance) {
this.balance = initialBalance;
}
public double getBalance() {
return balance;
}
public void setBalance(double balance) {
this.balance = balance;
notifyObservers();
}
public void addObserver(Observer observer) {
observers.add(observer);
}
public void removeObserver(Observer observer) {
observers.remove(observer);
}
public void notifyObservers() {
for (Observer observer : observers) {
observer.update("Balance updated: " + balance);
}
}
public void performOperation(OperationStrategy strategy, double amount) {
strategy.execute(this, amount);
}
// 模板方法
public void executeOperation(double amount) {
preOperation();
performOperation(createOperationStrategy(), amount);
postOperation();
}
protected abstract void preOperation();
protected abstract OperationStrategy createOperationStrategy();
protected abstract void postOperation();
}
// 储蓄账户类
class SavingsAccount extends Account {
public SavingsAccount(double initialBalance) {
super(initialBalance);
}
@Override
protected void preOperation() {
System.out.println("Savings Account: Pre-operation.");
}
@Override
protected OperationStrategy createOperationStrategy() {
return new DepositStrategy();
}
@Override
protected void postOperation() {
System.out.println("Savings Account: Post-operation.");
}
}
// 支票账户类
class CheckingAccount extends Account {
public CheckingAccount(double initialBalance) {
super(initialBalance);
}
@Override
protected void preOperation() {
System.out.println("Checking Account: Pre-operation.");
}
@Override
protected OperationStrategy createOperationStrategy() {
return new WithdrawStrategy();
}
@Override
protected void postOperation() {
System.out.println("Checking Account: Post-operation.");
}
}