public class MD5Check { /** * 默认的密码字符串组合,用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合 */ protected char hexDigits[] = { ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘ }; protected MessageDigest messagedigest = null;
{ try { messagedigest = MessageDigest.getInstance("MD5"); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } } public String getFileMD5String(File file) throws IOException { InputStream fis; fis = new FileInputStream(file); byte[] buffer = new byte[1024]; int numRead = 0; while ((numRead = fis.read(buffer)) > 0) { messagedigest.update(buffer, 0, numRead); } fis.close(); return bufferToHex(messagedigest.digest()); }
public String getFileMD5String(InputStream in) throws IOException { byte[] buffer = new byte[1024]; int numRead = 0; while ((numRead = in.read(buffer)) > 0) { messagedigest.update(buffer, 0, numRead); } in.close(); return bufferToHex(messagedigest.digest()); } private String bufferToHex(byte bytes[]) { return bufferToHex(bytes, 0, bytes.length); } private String bufferToHex(byte bytes[], int m, int n) { StringBuffer stringbuffer = new StringBuffer(2 * n); int k = m + n; for (int l = m; l < k; l++) { appendHexPair(bytes[l], stringbuffer); } return stringbuffer.toString(); } private void appendHexPair(byte bt, StringBuffer stringbuffer) { char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换 // 为逻辑右移,将符号位一起右移,此处未发现两种符号有何不同 char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换 stringbuffer.append(c0); stringbuffer.append(c1); } }