RFR(JDK11/NIO) 8202285: (fs) Add a method to Files for comparing file contents

Daniel Fuchs daniel.fuchs at oracle.com
Fri Apr 27 10:58:56 UTC 2018

Hi Joe,

On the specification side, I think I would reword the API
documentation to first explain how the method checks the
content of the two files.

The fact that it doesn't check the actual content if
the two files are 'the same' is kind of an optimization.

So I would suggest to invert the order of the two paragraph
in the documentation, and combine them into one - something like:

1536      * <p>
           * This method first calls {@link 
#isSameFile(java.nio.file.Path, java.nio.file.Path) isSameFile(path, 
path2)} to determine whether the two files are the same.
1537      * If {@code isSameFile(path, path2)} returns false, this 
method will proceed
1538      * to read the files and compare them byte by byte to determine 
if they contain
1539      * the same contents.
           * Otherwise, this method will return true without further
           * processing.

On the implementation side I don't think it's reasonable to call
readAllBytes() and hold the content of the two files in memory
for comparing their content, especially if it's to discover that
the first byte differs.

Some lock-step reading of the two files would seem more appropriate.

best regards,

-- daniel

On 27/04/2018 05:51, Joe Wang wrote:
> Hi,
> Considering extending isSameFile to add isSameContent to Files. Please 
> review.
> JBS: https://bugs.openjdk.java.net/browse/JDK-8202285
> webrev: http://cr.openjdk.java.net/~joehw/jdk11/8202285/webrev/
> specdiff: 
> http://cr.openjdk.java.net/~joehw/jdk11/8202285/specdiff/java/nio/file/Files.html 
> Thanks,
> Joe

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