import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class Md5Util {   
/**    
* 给指定字符串按照md5算法去加密   
 * @param psd 需要加密的字符串    
* @return  返回字符串     
*/  
 public static String encoder(String psd) {     
 try {        
 //1,指定加密算法类型         
MessageDigest digest = MessageDigest.getInstance("MD5");        
 //2,将需要加密的字符串中转换成byte类型的数组,然后进行随机哈希过程        
 byte[] bs = digest.digest(psd.getBytes());
//       System.out.println(bs.length);         
//3,循环遍历bs,然后让其生成32位字符串,固定写法        
 //4,拼接字符串过程         
StringBuffer stringBuffer = new StringBuffer();        
 for (byte b : bs) {           
 int i = b & 0xff;            
//int类型的i需要转换成16进制字符            
String hexString = Integer.toHexString(i);     i
f(hexString.length()<2){              
 hexString = "0"+hexString;           
 }            
stringBuffer.append(hexString);         
}                 
return stringBuffer.toString();    
  } catch (NoSuchAlgorithmException e) {  
       e.printStackTrace();     
 }      return "";  
 }
}