java 简单加密

package Case.Encryption;
import java.util.*;

public abstract class Cipher {
/** 
 * 所有的加密技术的基本操作都是用encrypt（）和decrypt（）方法对消息
 * 进行分解和组合，其中消息是用空格分隔的字符串，除了encrypt（）和decrypt（）
 * 外每个加密类还需要encode（）和decode（）方法对每一个单词按照特定的算法
 * 规则进行编码，。例如Caesar Cipher 和 Transpose Clipher
 *   按照设想由于加密都有相同的方法，因此首先定义一个通用的类Cipher类
 *   封装公用的方法。
 * 
 * */
  public String encrypt(String s){
      
      StringBuffer result=new StringBuffer();
      StringTokenizer words=new StringTokenizer(s);
      while(words.hasMoreTokens()){
          result.append(encode(words.nextToken())+"");
      }
      return result.toString();
  }

  public String decrypt(String s)
  {
      StringBuffer result=new StringBuffer();
      StringTokenizer words=new StringTokenizer(s);
      while(words.hasMoreTokens())
      {
          result.append(decode(words.nextToken())+"");
          
      }
      return result.toString();
      
      
  }
  public abstract String encode(String word);
  public abstract String decode(String woid);
    
}

package Case.Encryption;

public class Caesar extends Cipher{

    @Override
    public String encode(String word) {
        // TODO Auto-generated method stub
        StringBuffer result =new StringBuffer();
        for(int k=0;k<word.length();k++)
        {
            char ch=word.charAt(k);
            ch=(char)(‘a‘+(ch-‘a‘+3)%26);//?正则表达式
            result.append(ch);
        }
        return result.toString();
    }

    @Override
    public String decode(String word) {
        // TODO Auto-generated method stub
        StringBuffer result =new StringBuffer();
        for(int k=0;k<word.length();k++)
        {
            char ch=word.charAt(k);
            ch=(char)(‘a‘+(ch-‘a‘+23)%26);//?正则表达式
            result.append(ch);
        }
        return result.toString();
    }

}

package Case.Encryption;
/**本例采用的是最简单的翻转易位方法，也可以采用其他的易位方法*/
public class Transpose extends Cipher{

    @Override
    public String encode(String word) {
        // TODO Auto-generated method stub
        StringBuffer result =new StringBuffer();
        
        return result.reverse().toString();
    }

    @Override
    public String decode(String word) {
        // TODO Auto-generated method stub
        return encode(word);
    }
    
}

 1 package Case.Encryption;
 2 
 3 public class TestEncrypt {
 4     public static void main(String[] args) {
 5         Caesar caesar =new Caesar();
 6         String plain ="this is the secret message.";
 7         String secret=caesar.encrypt(plain);
 8         String decrypt=caesar.decrypt(secret);
 9         System.out.println("*********Caesar Cipher Encryption**********");
10         System.out.println("PlainText: "+plain);
11         System.out.println("Encrypted: "+secret);
12         System.out.println("Decrypted: "+decrypt);
13         
14         Transpose ts=new Transpose();
15         String tsecret=ts.encrypt(plain);
16         String tdecrypt=ts.decrypt(secret);
17         System.out.println("**********Transpose Cipher Encryption**********");
18         System.out.println("PlainText: "+plain);
19         System.out.println("Encrypted: "+tsecret);
20         System.out.println("Decrypted: "+tdecrypt);
21     }
22 
23 }