import java.io.File;  import java.io.FileInputStream;  import java.io.IOException;  import java.nio.MappedByteBuffer;  import java.nio.channels.FileChannel;  import java.security.MessageDigest;  import java.security.NoSuchAlgorithmException;    public class FileMd5Utils {       protected static char hexDigits[] = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};            protected static MessageDigest messageDigest = null;            static{              try{                    messageDigest = MessageDigest.getInstance("MD5");                }catch (NoSuchAlgorithmException e) {                    System.err.println(FileMd5Utils.class.getName()+"初始化失败，MessageDigest不支持MD5Util.");                    e.printStackTrace();                }            }              /**            * 计算文件的MD5            * @param fileName 文件的绝对路径            * @return            * @throws IOException            */            public static String getFileMD5String(String fileName) throws IOException{                File f = new File(fileName);                return getFileMD5String(f);            }              /**            * 计算文件的MD5，重载方法            * @param file 文件对象            * @return            * @throws IOException            */            public static String getFileMD5String(File file) throws IOException{                FileInputStream in = new FileInputStream(file);                FileChannel ch = in.getChannel();                MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());                messageDigest.update(byteBuffer);                return bufferToHex(messageDigest.digest());            }              private static String bufferToHex(byte bytes[]) {               return bufferToHex(bytes, 0, bytes.length);            }              private static 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 static void appendHexPair(byte bt, StringBuffer stringbuffer) {               char c0 = hexDigits[(bt & 0xf0) >> 4];               char c1 = hexDigits[bt & 0xf];               stringbuffer.append(c0);               stringbuffer.append(c1);            }              public static void main(String[] args) throws IOException {                String fileName = "F:\\test01\\1.txt";              String str = "d0970714757783e6cf17b26fb8e2298f";              String str2 = "ea3ed20b6b101a09085ef09c97da1597";              System.out.println(str.equals(str2));              System.out.println(getFileMD5String(fileName));          }    }