Java的MD5加密和解密类

简单MD5 类 

import  java.security.*;  
import  java.security.spec.*;  
  
class  MD5_test {  
 public   final   static  String MD5(String s) {  
  char  hexDigits[] = {  '0' ,  '1' ,  '2' ,  '3' ,  '4' ,  '5' ,  '6' ,  '7' ,  '8' ,  '9' ,  
    'a' ,  'b' ,  'c' ,  'd' ,  'e' ,  'f'  };  
  try  {  
   byte [] strTemp = s.getBytes();  
   MessageDigest mdTemp = MessageDigest.getInstance("MD5" );  
   mdTemp.update(strTemp);  
   byte [] md = mdTemp.digest();  
   int  j = md.length;  
   char  str[] =  new   char [j *  2 ];  
   int  k =  0 ;  
   for  ( int  i =  0 ; i < j; i++) {  
    byte  byte0 = md[i];  
    str[k++] = hexDigits[byte0 >>> 4  &  0xf ];  
    str[k++] = hexDigits[byte0 & 0xf ];  
   }  
   return   new  String(str);  
  } catch  (Exception e) {  
   return   null ;  
  }  
 }  
  
 public   static   void  main(String[] args) {  
  // MD5_Test aa = new MD5_Test();   
  System.out.print(MD5_test.MD5("b" ));  
 }  
}  

加密--解密 MD5类

import java.security.MessageDigest;  
  
  
public class MD5andKL {  
 // MD5加码。32位  
 public static String MD5(String inStr) {  
  MessageDigest md5 = null;  
  try {  
   md5 = MessageDigest.getInstance("MD5");  
  } catch (Exception e) {  
   System.out.println(e.toString());  
   e.printStackTrace();  
   return "";  
  }  
  char[] charArray = inStr.toCharArray();  
  byte[] byteArray = new byte[charArray.length];  
  
  for (int i = 0; i < charArray.length; i++)  
   byteArray[i] = (byte) charArray[i];  
  
  byte[] md5Bytes = md5.digest(byteArray);  
  
  StringBuffer hexValue = new StringBuffer();  
  
  for (int i = 0; i < md5Bytes.length; i++) {  
   int val = ((int) md5Bytes[i]) & 0xff;  
   if (val < 16)  
    hexValue.append("0");  
   hexValue.append(Integer.toHexString(val));  
  }  
  
  return hexValue.toString();  
 }  
  
 // 可逆的加密算法  
 public static String KL(String inStr) {  
  // String s = new String(inStr);  
  char[] a = inStr.toCharArray();  
  for (int i = 0; i < a.length; i++) {  
   a[i] = (char) (a[i] ^ 't');  
  }  
  String s = new String(a);  
  return s;  
 }  
  
 // 加密后解密  
 public static String JM(String inStr) {  
  char[] a = inStr.toCharArray();  
  for (int i = 0; i < a.length; i++) {  
   a[i] = (char) (a[i] ^ 't');  
  }  
  String k = new String(a);  
  return k;  
 }  
   
 // 测试主函数  
 public static void main(String args[]) {  
  String s = new String("a");  
  System.out.println("原始：" + s);  
  System.out.println("MD5后：" + MD5(s));  
  System.out.println("MD5后再加密：" + KL(MD5(s)));  
  System.out.println("解密为MD5后的：" + JM(KL(MD5(s))));  
 }  
}