Java get file MD5 check code

Thunder Download the core idea is to verify the MD5 value of the file, two files if the MD5 is the same file.

When a user requests to download a file, it MD5 the URL that owns the file based on the file retained in the database.

Hooks a user request to this URL and mimics a false breakpoint continuation request, stitching a normal file from several URLs.

Check the information, Java can also implement the file MD5 check code acquisition, the code is as follows:

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) {
Span style= "FONT-SIZE:18PX;" >    system.err.println (MD5Util.class.getName () + "initialization failed, MessageDigest does not support 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);
&NBSP;&NBSP;&NBSP;}
   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 ();

2ea3e66ac37df7610f5bd322ec4ffe48 670M 11s Kuri dual-core 1.66G 2G memory
File Big = new file ("e:/new folder. rar");

String md5=getfilemd5string (BIG);

Long end = System.currenttimemillis ();
SYSTEM.OUT.PRINTLN ("MD5:" +md5+ "Time:" + ((end-begin)/1000) + "s");
}

}

Reprinted from: http://blog.sina.com.cn/s/blog_53d3c24a0100mpm1.html

Java get file MD5 check code