JAVA实现MD5加密

	private static String getMd5(String str) {
		try {
			System.out.println("param--" + str);
			MessageDigest md = MessageDigest.getInstance("MD5");
			md.update(str.getBytes());
			
			byte[] b = md.digest();
			int i;
			StringBuffer buf = new StringBuffer();
			for (int offset = 0; offset < b.length; offset++) {  
				i = b[offset];  
				if (i < 0)  
					i += 256;  
				if (i < 16)  
					buf.append("0");  
				buf.append(Integer.toHexString(i));  
			}
			String md5Str = buf.toString().toUpperCase();
			System.out.println("sign--" + md5Str);
			return md5Str;
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		return null;
	}