Java 中，如何获取文件的MD5值呢？如何比较两个文件是否完全相同呢？
Java代码
- /**
- * Get MD5 of one file:hex string,test OK!
- *
- * @param file
- * @return
- */
- public static String getFileMD5(File file) {
- if (!file.exists() || !file.isFile()) {
- return null;
- }
- MessageDigest digest = null;
- FileInputStream in = null;
- byte buffer[] = new byte[1024];
- int len;
- try {
- digest = MessageDigest.getInstance("MD5");
- in = new FileInputStream(file);
- while ((len = in.read(buffer, 0, 1024)) != NEGATIVE_ONE) {
- digest.update(buffer, 0, len);
- }
- in.close();
- } catch (Exception e) {
- e.printStackTrace();
- return null;
- }
- BigInteger bigInt = new BigInteger(1, digest.digest());
- return bigInt.toString(16);
- }
- /***
- * Get MD5 of one file！test ok!
- *
- * @param filepath
- * @return
- */
- public static String getFileMD5(String filepath) {
- File file = new File(filepath);
- return getFileMD5(file);
- }
- /**
- * MD5 encrypt,test ok
- *
- * @param data
- * @return byte[]
- * @throws Exception
- */
- public static byte[] encryptMD5(byte[] data) throws Exception {
- MessageDigest md5 = MessageDigest.getInstance(SystemUtil.KEY_MD5);
- md5.update(data);
- return md5.digest();
- }
- public static byte[] encryptMD5(String data) throws Exception {
- return encryptMD5(data.getBytes(SystemUtil.CHARSET_ISO88591));
- }
- /***
- * compare two file by Md5
- *
- * @param file1
- * @param file2
- * @return
- */
- public static boolean isSameMd5(File file1,File file2){
- String md5_1=SystemUtil.getFileMD5(file1);
- String md5_2=SystemUtil.getFileMD5(file2);
- return md5_1.equals(md5_2);
- }
- /***
- * compare two file by Md5
- *
- * @param filepath1
- * @param filepath2
- * @return
- */
- public static boolean isSameMd5(String filepath1,String filepath2){
- File file1=new File(filepath1);
- File file2=new File(filepath2);
- return isSameMd5(file1, file2);
- }
测试（使用junit）：
Java代码
- @Test
- public void test_getFileMD5() throws Exception{
- String filepath="D:\\download\\3_尚学堂_UML概览.avi";
- // File file=new File(filepath);
- String md5_1=SystemUtil.getFileMD5(filepath);
- System.out.println(md5_1);
- byte[]bytes=FileUtils.readBytes4file(filepath);
- byte[]md5=SystemUtil.encryptMD5(bytes);
- String md5_2=SystemUtil.toHexString(md5);
- System.out.println(md5_2);
- Assert.assertEquals(md5_1, md5_2);
- }
