状态模式
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。
在某银行系统定义的账户有三种状态： (1) 如果账户(Account)中余额(balance)大于等于0，此时账户的状态为绿色(GreenState)，即正常状态，表示既可以向该账户存款(deposit)也可以从该账户取款(withdraw)； (2) 如果账户中余额小于0，并且大于等于-1000，则账户的状态为黄色(YellowState)，即欠费状态，此时既可以向该账户存款也可以从该账户取款； (3) 如果账户中余额小于-1000，那么账户的状态为红色(RedState)，即透支状态，此时用户只能向该账户存款，不能再从中取款。 现用状态模式来实现状态的转化问题，用户只需要执行简单的存款和取款操作，系统根据余额数量自动转换到相应的状态
c++实现
#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="透支状态"; } void withdraw(double amount){cout<<"您的账户处于透支状态，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="欠费状态"; } void stateCheck(); }; class GreenState:public AccountState{ public: GreenState(double balance,Account *acc) { this->balance = balance; this->acc = acc; this->stateName="正常状态"; } GreenState(AccountState *state) { this->acc=state->acc; this->balance=state->balance; this->stateName="正常状态"; } 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<<"账户余额："<<this->balance<<endl; cout<<"现在账户状态："<<acc->getState()->stateName<<endl; } void AccountState::withdraw(double amount){ cout<<acc->getOwner()<<"取款"<<amount<<endl; this->balance-=amount; stateCheck(); cout<<"账户余额："<<this->balance<<endl; cout<<"现在账户状态："<<acc->getState()->stateName<<endl; } Account::Account(string owner,double init){ this->owner=owner; this->state=new GreenState(init,this); cout<<"恭喜"<<this->owner<<"开户成功！银行卡初始金额："<<init<<endl; cout<<"------------------------------"<<endl; } int main(){ Account *account=new Account("张三",1000); account->deposit(100); account->withdraw(500); account->withdraw(700); account->withdraw(1000); return 0; }
java实现
package state; //账户类 public class Account { private AccountState state; private String name; public Account(String name,double init_money) { this.name = name; state=new Green(init_money,this); System.out.println("余额："+init_money); } public void setState(AccountState state) { this.state = state; } //存款 public void deposit(double money){ state.deposit(money); System.out.println("余额："+this.state.economy); } // 取款 public void withDraw(double money){ state.withDraw(money); System.out.println("余额:"+this.state.economy); } }
package state; public abstract class AccountState { protected Account account; protected double economy; public abstract void check(); public abstract void deposit(double m); public abstract void withDraw(double m); }
package state; //正常状态 money>0 public class Green extends AccountState{ public Green(double money,Account acc) { economy=money; account=acc; } @Override public void check() { if(economy>0){ System.out.println("---正常状态---"); account.setState(new Green(economy,account)); }else if(economy<=0&&economy>=-1000){ System.out.println("---欠费状态---"); account.setState(new Yellow(economy,account)); }else if(economy<-1000){ System.out.println("---透支状态---"); account.setState(new Red(economy,account)); } } @Override public void deposit(double m) { economy += m; check(); } @Override public void withDraw(double m) { economy -= m; check(); } }
package state; //警告状态 money<0&&money>-1000 public class Yellow extends AccountState{ public Yellow(double m,Account acc){ economy=m; account=acc; } @Override public void check() { if(economy>0){ System.out.println("---正常状态---"); account.setState(new Green(economy,account)); }else if(economy<=0&&economy>=-1000){ System.out.println("---欠费状态---"); account.setState(new Yellow(economy,account)); }else if(economy<-1000){ System.out.println("---透支状态---"); account.setState(new Red(economy,account)); } } @Override public void deposit(double m) { economy += m; check(); } @Override public void withDraw(double m) { economy -= m; check(); } }
