年末整理十四 MD5加密

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
 /** 
     * MD5 加密 
     */  
    public static String getMD5Str(String str) {  
        MessageDigest messageDigest = null;  
  
        try {  
            messageDigest = MessageDigest.getInstance("MD5");           
           
            messageDigest.reset();  
            messageDigest.update(str == null ? "".getBytes("UTF-8") : str.getBytes("UTF-8"));
        } catch (NoSuchAlgorithmException e) {  
            System.out.println("NoSuchAlgorithmException caught!");  
            System.exit(-1);  
        } catch (UnsupportedEncodingException e) {  
            e.printStackTrace();  
        }  
  
        byte[] byteArray = messageDigest.digest();
        StringBuffer md5StrBuff = new StringBuffer();  
  
        for (int i = 0; i < byteArray.length; i++) {              
            if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)  
                md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));  
            else  
                md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));  
        }  
        return md5StrBuff.toString();  
    } 
jdk5 以上都是自帶加密的jar；