实验二十二

1.     源代码；

// Account.java 

public class Account { 

    private String owner; 

    private AccountState state; 

    private double balance; 

 

    public Account(String owner, double initBalance) { 

        this.owner = owner; 

        this.balance = initBalance; 

        this.state = new GreenState(this, balance); 

    } 

 

    public void setState(AccountState state) { 

        this.state = state; 

    } 

 

    public AccountState getState() { 

        return state; 

    } 

 

    public String getOwner() { 

        return owner; 

    } 

 

    public void deposit(double amount) { 

        state.deposit(amount); 

        balance += amount; 

        state.stateCheck(); 

    } 

 

    public void withdraw(double amount) { 

        state.withdraw(amount); 

        balance -= amount; 

        state.stateCheck(); 

    } 

 

    public double getBalance() { 

        return balance; 

    } 

} 

 

// AccountState.java 

abstract class AccountState { 

    protected Account acc; 

    protected double balance; 

    protected String stateName; 

 

    public AccountState(Account acc, double balance) { 

        this.acc = acc; 

        this.balance = balance; 

    } 

 

    public abstract void deposit(double amount); 

    public abstract void withdraw(double amount); 

    public abstract void stateCheck(); 

} 

 

// GreenState.java 

class GreenState extends AccountState { 

   

    public GreenState(Account acc, double balance) { 

        super(acc, balance); 

        this.stateName = "Green State"; 

    } 

 

    @Override 

    public void deposit(double amount) { 

        System.out.println("Deposit of $" + amount + " into " + acc.getOwner() + "'s account in Green State."); 

    } 

 

    @Override 

    public void withdraw(double amount) { 

        if (amount <= balance) { 

            System.out.println("Withdrawal of $" + amount + " from " + acc.getOwner() + "'s account in Green State."); 

        } else { 

            System.out.println("Withdrawal of $" + amount + " failed. Insufficient funds!"); 

            acc.setState(new RedState(acc)); 

        } 

    } 

 

    @Override 

    public void stateCheck() { 

        if (balance < 0) { 

            acc.setState(new RedState(acc)); 

        } 

    } 

} 

 

// RedState.java 

class RedState extends AccountState { 

 

    public RedState(Account acc) { 

        super(acc, acc.getBalance()); 

        this.stateName = "Red State"; 

    } 

 

    @Override 

    public void deposit(double amount) { 

        System.out.println("Deposit of $" + amount + " into " + acc.getOwner() + "'s account in Red State."); 

        balance += amount; 

        stateCheck(); 

    } 

 

    @Override 

    public void withdraw(double amount) { 

        System.out.println("Withdrawal of $" + amount + " failed in Red State. Account is overdrawn!"); 

    } 

 

    @Override 

    public void stateCheck() { 

        if (balance >= 0) { 

            acc.setState(new GreenState(acc, balance)); 

        } 

    } 

} 

 

// YellowState.java (placeholder) 

class YellowState extends AccountState { 

   

    public YellowState(Account acc) { 

        super(acc, acc.getBalance()); 

        this.stateName = "Yellow State"; 

    } 

 

    @Override 

    public void deposit(double amount) { 

        // Implement behavior for Yellow State 

    } 

 

    @Override 

    public void withdraw(double amount) { 

        // Implement behavior for Yellow State 

    } 

 

    @Override 

    public void stateCheck() { 

        // Implement state transition checks if necessary 

    } 

}

 

// BankClient.java 

public class BankClient { 

    public static void main(String[] args) { 

        Account account = new Account("John Doe", 100.0); 

        System.out.println("Account created for: " + account.getOwner() + " with initial balance: $" + account.getBalance()); 

 

        // Test deposits 

        account.deposit(50.0); // Should succeed 

        System.out.println("Current balance: $" + account.getBalance()); 

 

        // Test withdrawals 

        account.withdraw(30.0); // Should succeed 

        System.out.println("Current balance: $" + account.getBalance()); 

 

        // Test withdrawal that overloads 

        account.withdraw(150.0); // Should fail and switch to RedState 

        System.out.println("Current balance: $" + account.getBalance()); 

 

        // Test a deposit after overdraft 

        account.deposit(50.0); // Should succeed and move to GreenState 

        System.out.println("Current balance: $" + account.getBalance()); 

    } 

}