Re: How to check two text files have the same content or not?

From:
Eric Sosman <Eric.Sosman@sun.com>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 03 Sep 2008 13:25:24 -0400
Message-ID:
<1220462663.212352@news1nwk>
www wrote:

Hi,

I need a method to check two text files whether or not have the same
content. The file is small, about 10 lines. But I don't like to compare
them line by line or jam all lines into one line and compare that line.
I thought there should be some way easier.

I googled and have written the following method. But it does not work
correctly. Even the two files have different content, the method returns
true.

Thank you very much for your help.

    /**
     * Check two files' content are the same or not. The two files are
allowed to be in different locations. If their
     * content inside are the same, return true; otherwise, return false.
     * <p>
     * Note: is possible that the replacement does not alter the checksum?
     */
    public static boolean checkTwoFilesEqual(final File fileA, final
File fileB) throws IOException
    {
        final CheckedInputStream cisA = new CheckedInputStream(new
FileInputStream(fileA), new CRC32());
        final CheckedInputStream cisB = new CheckedInputStream(new
FileInputStream(fileB), new CRC32());

        if(cisA.getChecksum().getValue() == cisB.getChecksum().getValue())
        {
            return true;
        }

        //not equal
        return false;
    }


     The checksum is computed from the bytes that have been read. You
never read any bytes, so both checksums remain in their initial state,
no matter what the files contain.

     To make the checksums reflect the bytes in the files, you need
to read each stream all the way to the end. And as long as you're
reading the actual bytes, why settle for an answer that can only
be "definitely unequal" or "maybe equal?" Forget about the checksums
and compare the bytes themselves.

     Also, it's considered good manners to close streams when you're
finished with them ...

--
Eric.Sosman@sun.com

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