接口的实例研究

来看一个使用接口的实例，创建一个接口Icipher，用来指定一个加密和字符串的方法。

接口定义：

namespace Cipher{ public interface ICipher { //加密 string encode(string str); //解密 string decode(string str); }}

下面两个类实现了Icipher。

/*简单的易位代码，通过将每个字符都向高位一定一位来加密字符串*/ public class SimpleCipher:ICipher { public string encode(string str) { string ciphertext = ""; for (int i = 0; i < str.Length; ++i) { Console.WriteLine(i.ToString()+" "+(str[i] + 1).ToString()); ciphertext = ciphertext + (char)(str[i] + 1); } return ciphertext; } public string decode(string str) { string plaintext = ""; for (int i = 0; i < str.Length; ++i) { plaintext = plaintext + (char)(str[i] - 1); } return plaintext; }

/*通过将每个字符与一个16位的密钥进行XOR（异或）运算加密字符串*/ public class BitCipher : ICipher { ushort key; public BitCipher(ushort k) { key = k; } public string encode(string str) { string ciphertext = ""; for (int i = 0; i < str.Length; ++i) { ciphertext = ciphertext + (char)(str[i] ^ key); } return ciphertext; } public string decode(string str) { string plaintext = ""; for (int i = 0; i < str.Length; ++i) { plaintext = plaintext + (char)(str[i] ^ key); } return plaintext; }

 

虽然SimpleCipher和BitCipher在实现上完全不同，但他们都实现了ICipher接口。下面示范了两个类的用法：

static void Main(string[] args) { ICipher ciphRef; BitCipher bit = new BitCipher(27); SimpleCipher sc = new SimpleCipher(); string plain; string coded; ciphRef = sc; Console.WriteLine("Using simple cipher."); plain = "testing"; coded = ciphRef.encode(plain); Console.WriteLine("Cipher text:"+coded); plain = ciphRef.decode(coded); Console.WriteLine("Plain text:"+plain); ciphRef = bit; Console.WriteLine("/nUsing bitwise cipher."); plain = "testing"; coded = ciphRef.encode(plain); Console.WriteLine("Cipher text:"+coded); plain = ciphRef.decode(coded); Console.WriteLine("Plain text:"+plain); }

创建加密接口的好处在于，无论加密方法如何实现，只要类中实现了该接口，就可以以相同的方式访问它。