實驗：用Java程式碼模擬實現課堂上的“銀行賬戶”的例項，要求編寫客戶端測試程式碼模擬使用者存款和取款，注意賬戶物件狀態和行為的變化。

由於是c++，不像java那麼靈活，所以類的呼叫方面出了些許多問題，包括呼叫，出現了很多錯誤，不過好在都解決了。

程式碼：

#include<iostream>
using namespace std;
class Account;
class AccountState{
public:
    Account *acc;
   double balance;
   string stateName;
public:
     virtual
 
 void stateCheck()=0;
     void deposit(double amount);
     virtual void withdraw(double amount);
};
class Account{
private:
    AccountState *state;
    string owner;
public:
    Account(string owner,double init);

    void setState(AccountState *state) {
        this->state=state;
    }
    AccountState
 
* getState() {
        return this->state;
    }
    string getOwner() {
        return this->owner;
    }
    void deposit(double amount) {
        state->deposit(amount);
    }
    void withdraw(double amount) {
        state->withdraw(amount);
    }
};
class RedState :public AccountState{
 
public:
    RedState(AccountState *state) {
        this->balance = state->balance;
        this->acc = state->acc;
        this->stateName="透支狀態";
    }
    void withdraw(double amount){cout<<"您的賬戶處於透支狀態，不能取款！"<<endl;}
    void stateCheck();
};
class YellowState :public AccountState{
public:
    YellowState(AccountState *state) {
         this->balance = state->balance;
         this->acc = state->acc;
         this->stateName="欠費狀態";
    }
    void stateCheck();
};
class GreenState:public AccountState{
public:
     GreenState(double balance,Account *acc) {
        this->balance = balance;
        this->acc = acc;
        this->stateName="正常狀態";
    }
    GreenState(AccountState *state) {
        this->acc=state->acc;
        this->balance=state->balance;
        this->stateName="正常狀態";
    }
    void stateCheck() {
        if(balance>=-1000&&balance<0) {
            acc->setState(new YellowState(this));
        }else if(balance<-1000) {
            acc->setState(new RedState(this));
        }
        else{
            acc->setState(new GreenState(this));
        }
    }
};
void RedState::stateCheck(){
    if(balance>=-1000&&balance<0) {
            acc->setState(new YellowState(this));
        }else if(balance<-1000) {
            acc->setState(new RedState(this));
        }
        else {
            acc->setState(new GreenState(this));
        }
}
void YellowState::stateCheck() {
        if(balance>=-1000&&balance<0) {
            acc->setState(new YellowState(this));
        }else if(balance<-1000) {
            acc->setState(new RedState(this));
        }
        else{
            acc->setState(new GreenState(this));
        }
}
void AccountState::deposit(double amount){
        cout<<acc->getOwner()<<"存款"<<amount<<endl;
        this->balance+=amount;
        stateCheck();
        cout<<"賬戶餘額："<<this->balance<<endl;
        cout<<"現在賬戶狀態："<<acc->getState()->stateName<<endl;
    }
void AccountState::withdraw(double amount){
        cout<<acc->getOwner()<<"取款"<<amount<<endl;
        this->balance-=amount;
        stateCheck();
        cout<<"賬戶餘額："<<this->balance<<endl;
        cout<<"現在賬戶狀態："<<acc->getState()->stateName<<endl;
    }
Account::Account(string owner,double init){
    this->owner=owner;
    this->state=new GreenState(init,this);
    cout<<"恭喜"<<this->owner<<"開戶成功！銀行卡初始金額："<<init<<endl;
    cout<<"------------------------------"<<endl;
}
int main(){
        Account *account=new Account("張三",100);
        account->deposit(100);
        cout<<"------------------------------"<<endl;
        account->withdraw(500);
        cout<<"------------------------------"<<endl;
        account->deposit(1000);
        cout<<"------------------------------"<<endl;
        account->withdraw(2000);
        cout<<"------------------------------"<<endl;
        cout<<account->getState()->stateName;
        account->withdraw(100);
        cout<<"------------------------------"<<endl;
        account->deposit(2000);
        cout<<"------------------------------"<<endl;
        return 0;
}

#include<iostream>
using namespace std;
class Account;
class AccountState{
public:
    Account *acc;
   double balance;
   string stateName;
public:
    virtual void stateCheck()=0;
    virtual void deposit(double amount)=0;
    virtual void withdraw(double amount)=0;
};
class Account{
private:
    AccountState *state;
    string owner;
public:
    Account(string owner,double init);

    void setState(AccountState *state) {
        this->state=state;
    }
    AccountState* getState() {
        return this->state;
    }
    string getOwner() {
        return this->owner;
    }
    void checkState(){
        state->stateCheck();
    }
    void deposit(double amount) {
        cout<<this->owner<<"存款"<<amount<<endl;
        state->deposit(amount);
        cout<<"賬戶餘額："<<state->balance<<endl;
        cout<<"現在賬戶狀態："<<state->stateName<<endl;
    }
    void withdraw(double amount) {
        cout<<this->owner<<"取款"<<amount<<endl;
        state->withdraw(amount);
        cout<<"賬戶餘額"<<state->balance<<endl;
        cout<<"現在賬戶狀態："<<state->stateName<<endl;
    }
};
class RedState :public AccountState{
public:
    RedState(AccountState *state) {
        this->balance = state->balance;
        this->acc = state->acc;
        this->stateName="透支狀態";
    }
    void stateCheck();
    void deposit(double amount) {
        this->balance+=amount;
        stateCheck();
    }
    void withdraw(double amount) {
          cout<<"您的賬戶處於透支狀態，不能取款！"<<endl;
    }
};
class YellowState :public AccountState{
public:
    YellowState(AccountState *state) {
         this->balance = state->balance;
         this->acc = state->acc;
         this->stateName="欠費狀態";
    }
    void stateCheck();
    void deposit(double amount) {
        this->balance+=amount;
        stateCheck();
    }
    void withdraw(double amount) {
        this->balance-=amount;
        stateCheck();
    }
};
class GreenState:public AccountState{
public:
     GreenState(double balance,Account *acc) {
        this->balance = balance;
        this->acc = acc;
        this->stateName="正常狀態";
    }
    GreenState(AccountState *state) {
        this->acc=state->acc;
        this->balance=state->balance;
        this->stateName="正常狀態";
    }
    void stateCheck() {
        if(balance>=-1000&&balance<0) {
            acc->setState(new YellowState(this));
        }else if(balance<-1000) {
            acc->setState(new RedState(this));
        }
        else{
            acc->setState(new GreenState(this));
        }
    }
    void deposit(double amount) {
        this->balance+=amount;
        stateCheck();
    }
    void withdraw(double amount) {
        this->balance-=amount;
        stateCheck();
    }
};
void RedState::stateCheck(){
    if(balance>=-1000&&balance<0) {
            acc->setState(new YellowState(this));
        }else if(balance<-1000) {
            acc->setState(new RedState(this));
        }
        else {
            acc->setState(new GreenState(this));
        }
}
void YellowState::stateCheck() {
        if(balance>=-1000&&balance<0) {
            acc->setState(new YellowState(this));
        }else if(balance<-1000) {
            acc->setState(new RedState(this));
        }
        else{
            acc->setState(new GreenState(this));
        }
}
Account::Account(string owner,double init){
    this->owner=owner;
    this->state=new GreenState(init,this);
    cout<<"恭喜"<<this->owner<<"開戶成功！銀行卡初始金額："<<init<<endl;
    cout<<"------------------------------"<<endl;
}
int main(){
        Account *account=new Account("張三",100);
        account->deposit(100);
        cout<<"------------------------------"<<endl;
        account->withdraw(500);
        cout<<"------------------------------"<<endl;
        account->deposit(1000);
        cout<<"------------------------------"<<endl;
        account->withdraw(2000);
        cout<<"------------------------------"<<endl;
        account->withdraw(100);
        cout<<"------------------------------"<<endl;
        account->deposit(2000);
        cout<<"------------------------------"<<endl;
        return 0;
}

兩種方法執行結果：

個人覺得第一種比較好。