MD5加密、加密后在加密和解密

public class test {

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( "china" );   
  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))));   
}   

}