MD5 生成文件的MD5码

/** * Copyright 2012 * * All right reserved *  * Created on 2012-8-31下午5:43:58 */package com.test.md5;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import org.apache.log4j.Logger;/** *  * @author xuepeng *  */public class MD5Checksum {private static Logger LOGGER = Logger.getLogger(MD5Checksum.class);private static byte[] createChecksum(String filename) {InputStream fis = null;try {fis = new FileInputStream(filename);byte[] buffer = new byte[1024];MessageDigest complete = MessageDigest.getInstance("MD5");int numRead = -1;while ((numRead = fis.read(buffer)) != -1) {complete.update(buffer, 0, numRead);}return complete.digest();} catch (FileNotFoundException e) {LOGGER.error(e.getMessage(), e);} catch (NoSuchAlgorithmException e) {LOGGER.error(e.getMessage(), e);} catch (IOException e) {LOGGER.error(e.getMessage(), e);} finally {try {if (null != fis) {fis.close();}} catch (IOException e) {LOGGER.error(e.getMessage(), e);}}return null;}// see this How-to for a faster way to convert// a byte array to a HEX stringpublic static String getMD5Checksum(String filename) {if (!new File(filename).isFile()) {LOGGER.error("Error: " + filename+ " is not a valid file.");return null;}byte[] b = createChecksum(filename);if(null == b){LOGGER.error("Error:create md5 string failure!");return null;}StringBuilder result = new StringBuilder();for (int i = 0; i < b.length; i++) {result.append(Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1));}return result.toString();}public static void main(String args[]) {try {long beforeTime = System.currentTimeMillis();String path = "C:\\Users\\user\\Desktop\\work_shedule.txt";String before = "999E42920C54CF7D66190731CD54F0E6".toLowerCase();String md5 = getMD5Checksum(path);System.out.println(md5);System.out.println(md5.equals(before));File file = new File(path);System.out.println(path+ "'s size is : " +file.length()+" bytes, it consumes " + (System.currentTimeMillis() - beforeTime) + " ms.");} catch (Exception e) {LOGGER.error(e.getMessage(), e);}}}