How to compare two files using MD5?

Hi,all:
How to compare two files to know if they're the same without any difference?I want to use MD5, but I just konw how get a message digest of a string. How to get a message digest of a file? Or there is other method to compare two files?
Thanks advance!

This is starting to sound rather a lot like a homework problem.
An MD5 message digest is simply a 16 byte array. To compare two message digests...
byte[] md5incoming = ...
byte[] md5comparison = ...
if( md5incoming.equals(md5comparison) ) {
   System.out.println("MD5 Checksums match");
}To find out how to generate an MD5 checksum, please look up MessageDigest in the API documentation, and do a google search for "MD5 java"
In a networked scenario, there are two issues - firstly the performance in sending copies of files all over the place (imagine if it's a 10Gb file to be compared over a 14.4K modem link, this would take a while). Secondly, the network link itself might insert an error in the file and you'd get a false miss.
By only sending MD5 digests over the link, you simultaneously reduce the error (shorter files are less likely to be corrupted) and reduce the transmission time (16 bytes takes practically no time to transmit over damp string, let alone any sort of sensible device).
D.

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