1. 不好的代码（冗杂）

//业务操作
class Stream{
public：virtual char Read(int number)=0;virtual void Seek(int position)=0;virtual void Write(char data)=0;virtual ~Stream(){}
};//主体类
class FileStream: public Stream{
public:virtual char Read(int number){//读文件流}virtual void Seek(int position){//定位文件流}virtual void Write(char data){//写文件流}};class NetworkStream :public Stream{
public:virtual char Read(int number){//读网络流}virtual void Seek(int position){//定位网络流}virtual void Write(char data){//写网络流}};class MemoryStream :public Stream{
public:virtual char Read(int number){//读内存流}virtual void Seek(int position){//定位内存流}virtual void Write(char data){//写内存流}};//扩展操作
class CryptoFileStream :public FileStream{
public:virtual char Read(int number){//额外的加密操作...FileStream::Read(number);//读文件流}virtual void Seek(int position){//额外的加密操作...FileStream::Seek(position);//定位文件流//额外的加密操作...}virtual void Write(byte data){//额外的加密操作...FileStream::Write(data);//写文件流//额外的加密操作...}
};class CryptoNetworkStream : :public NetworkStream{
public:virtual char Read(int number){//额外的加密操作...NetworkStream::Read(number);//读网络流}virtual void Seek(int position){//额外的加密操作...NetworkStream::Seek(position);//定位网络流//额外的加密操作...}virtual void Write(byte data){//额外的加密操作...NetworkStream::Write(data);//写网络流//额外的加密操作...}
};class CryptoMemoryStream : public MemoryStream{
public:virtual char Read(int number){//额外的加密操作...MemoryStream::Read(number);//读内存流}virtual void Seek(int position){//额外的加密操作...MemoryStream::Seek(position);//定位内存流//额外的加密操作...}virtual void Write(byte data){//额外的加密操作...MemoryStream::Write(data);//写内存流//额外的加密操作...}
};class BufferedFileStream : public FileStream{//...
};class BufferedNetworkStream : public NetworkStream{//...
};class BufferedMemoryStream : public MemoryStream{//...
}class CryptoBufferedFileStream :public FileStream{
public:virtual char Read(int number){//额外的加密操作...//额外的缓冲操作...FileStream::Read(number);//读文件流}virtual void Seek(int position){//额外的加密操作...//额外的缓冲操作...FileStream::Seek(position);//定位文件流//额外的加密操作...//额外的缓冲操作...}virtual void Write(byte data){//额外的加密操作...//额外的缓冲操作...FileStream::Write(data);//写文件流//额外的加密操作...//额外的缓冲操作...}
};void Process(){//编译时装配CryptoFileStream *fs1 = new CryptoFileStream();BufferedFileStream *fs2 = new BufferedFileStream();CryptoBufferedFileStream *fs3 =new CryptoBufferedFileStream();}

2. 好的代码

//业务操作
class Stream{public：virtual char Read(int number)=0;virtual void Seek(int position)=0;virtual void Write(char data)=0;virtual ~Stream(){}
};//主体类
class FileStream: public Stream{
public:virtual char Read(int number){//读文件流}virtual void Seek(int position){//定位文件流}virtual void Write(char data){//写文件流}};class NetworkStream :public Stream{
public:virtual char Read(int number){//读网络流}virtual void Seek(int position){//定位网络流}virtual void Write(char data){//写网络流}};class MemoryStream :public Stream{
public:virtual char Read(int number){//读内存流}virtual void Seek(int position){//定位内存流}virtual void Write(char data){//写内存流}};//扩展操作class CryptoStream: public Stream {Stream* stream;//...public:CryptoStream(Stream* stm):stream(stm){}virtual char Read(int number){//额外的加密操作...stream->Read(number);//读文件流}virtual void Seek(int position){//额外的加密操作...stream->Seek(position);//定位文件流//额外的加密操作...}virtual void Write(byte data){//额外的加密操作...stream->Write(data);//写文件流//额外的加密操作...}
};class BufferedStream : public Stream{Stream* stream;//...public:BufferedStream(Stream* stm):stream(stm){}//...
};void Process(){//运行时装配FileStream* s1=new FileStream();CryptoStream* s2=new CryptoStream(s1);BufferedStream* s3=new BufferedStream(s1);BufferedStream* s4=new BufferedStream(s2);
}

3. 继续改进

//业务操作
class Stream{public：virtual char Read(int number)=0;virtual void Seek(int position)=0;virtual void Write(char data)=0;virtual ~Stream(){}
};//主体类
class FileStream: public Stream{
public:virtual char Read(int number){//读文件流}virtual void Seek(int position){//定位文件流}virtual void Write(char data){//写文件流}};class NetworkStream :public Stream{
public:virtual char Read(int number){//读网络流}virtual void Seek(int position){//定位网络流}virtual void Write(char data){//写网络流}};class MemoryStream :public Stream{
public:virtual char Read(int number){//读内存流}virtual void Seek(int position){//定位内存流}virtual void Write(char data){//写内存流}};//扩展操作DecoratorStream: public Stream{
protected:Stream* stream;//...DecoratorStream(Stream * stm):stream(stm){}};class CryptoStream: public DecoratorStream {public:CryptoStream(Stream* stm):DecoratorStream(stm){}virtual char Read(int number){//额外的加密操作...stream->Read(number);//读文件流}virtual void Seek(int position){//额外的加密操作...stream->Seek(position);//定位文件流//额外的加密操作...}virtual void Write(byte data){//额外的加密操作...stream->Write(data);//写文件流//额外的加密操作...}
};class BufferedStream : public DecoratorStream{Stream* stream;//...public:BufferedStream(Stream* stm):DecoratorStream(stm){}//...
};void Process(){//运行时装配FileStream* s1=new FileStream();CryptoStream* s2=new CryptoStream(s1);BufferedStream* s3=new BufferedStream(s1);BufferedStream* s4=new BufferedStream(s2);
}