读取文件MD5码流

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 MD5Util {

 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 nsaex) {
   System.err.println(MD5Util.class.getName() + "初始化失败，MessageDigest不支持MD5Util。");
   nsaex.printStackTrace();
  }
 }

 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());
 }

 public static String getMD5String(String s) {
  return getMD5String(s.getBytes());
 }

 public static String getMD5String(byte[] bytes) {
  messagedigest.update(bytes);
  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 boolean checkPassword(String password, String md5PwdStr) {
  String s = getMD5String(password);
  return s.equals(md5PwdStr);
 }

 public static void main(String[] args) throws IOException {
  long begin = System.currentTimeMillis();
  File big = new File("D:\\appUpload\\temp\\CMMB_Android_V2012110714-大塔+测试频道.apk");
  String md5 = getFileMD5String(big);

  long end = System.currentTimeMillis();
  System.out.println("md5:" + md5 + " time:" + ((end - begin) / 1000) + "s");
 }

}