今天完成软件设计实验二十二状态模式，以下为实验内容：

实验 22：状态模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容：

1、理解状态模式的动机，掌握该模式的结构；

2、能够利用状态模式解决实际问题。

[实验任务一]：银行账户

用Java代码模拟实现课堂上的“银行账户”的实例，要求编写客户端测试代码模拟用户存款和取款，注意账户对象状态和行为的变化。

实验要求：

1.     画出对应的类图；

2.     提交源代码；

// 账户状态接口
interface AccountState {
    void deposit(Account account, double amount);
    void withdraw(Account account, double amount);
}

// 正常状态
class NormalState implements AccountState {
    public void deposit(Account account, double amount) {
        account.setBalance(account.getBalance() + amount);
        System.out.println("Deposited " + amount + ". Balance is " + account.getBalance());
    }

    public void withdraw(Account account, double amount) {
        if (account.getBalance() >= amount) {
            account.setBalance(account.getBalance() - amount);
            System.out.println("Withdrew " + amount + ". Balance is " + account.getBalance());
        } else {
            System.out.println("Insufficient balance for withdrawal");
        }
    }
}

// 透支保护状态
class OverdraftState implements AccountState {
    public void deposit(Account account, double amount) {
        account.setBalance(account.getBalance() + amount);
        System.out.println("Deposited " + amount + ". Balance is " + account.getBalance());
        if (account.getBalance() > 0) {
            account.setState(new NormalState());
        }
    }

    public void withdraw(Account account, double amount) {
        if (account.getBalance() + 100 >= amount) {
            account.setBalance(account.getBalance() - amount);
            System.out.println("Withdrew " + amount + ". Balance is " + account.getBalance());
        } else {
            System.out.println("Insufficient balance for withdrawal");
        }
    }
}

// 冻结状态
class FrozenState implements AccountState {
    public void deposit(Account account, double amount) {
        System.out.println("Account is frozen. Deposit not allowed.");
    }

    public void withdraw(Account account, double amount) {
        System.out.println("Account is frozen. Withdrawal not allowed.");
    }
}

// 账户类
class Account {
    private double balance;
    private AccountState state;

    public Account(double balance) {
        this.balance = balance;
        this.state = new NormalState();
    }

    public double getBalance() {
        return balance;
    }

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

    public AccountState getState() {
        return state;
    }

    public void setState(AccountState state) {
        this.state = state;
    }

    public void deposit(double amount) {
        state.deposit(this, amount);
    }

    public void withdraw(double amount) {
        state.withdraw(this, amount);
    }
}

// 客户端测试代码
public class StatePatternTest {
    public static void main(String[] args) {
        Account account = new Account(1000);

        account.deposit(500);
        account.withdraw(200);
        account.withdraw(1500); // 触发透支保护

        account.deposit(1000);
        account.withdraw(500);