title: Java Files.copy replace existing deletes file entirely
body: <p>I have some code that is designed to open a local master file, make additions, and save the file both by overwriting the master file and overwriting a write protected copy on an accessible network location. This is done by saving the modified file to a temp file and then copying over the other two files.</p>
  
  <pre><code>String tempFileName= "File.tmp";
  String fileName= "File.xlsm";
  String serverPath="\\\\network path\\";
  File serverFile = new File(serverPath+fileName);
  
  Files.copy(Paths.get(tempFileName),Paths.get(fileName),
     StandardCopyOption.COPY_ATTRIBUTES,StandardCopyOption.REPLACE_EXISTING);
  
  if(serverFile.exists()){serverFile.setWritable(true, false);}
  
  Files.copy(Paths.get(tempFileName),Paths.get(serverPath+fileName),
     StandardCopyOption.COPY_ATTRIBUTES,StandardCopyOption.REPLACE_EXISTING);
  
  serverFile.setWritable(false,false);
  
  Files.delete(Paths.get(tempFileName));
  </code></pre>
  
  <p>This code works well most of the time however, some of the time the code completes successfully without exception but with the network location file deleted.  The local master file is saved and updated correctly but the file that should exist on the network is simply gone.</p>
  
  <p>What makes this more difficult is that i have been unable to reproduce this problem under any controlled circumstances. So i ask you for any guidance on how this could occur from a file copy/overwrite operation.</p>
  
  <p>Thank you</p>
  
  <p>UPDATE:</p>
  
  <p>I had a hunch and checked network access logs to the server file path.  The deletion of the file occurs if and only if the file is being accessed by a user other than the creator but not all of the time.  Again though, this is accessed as read only so a user having the file open should not affect overwriting a new version and most of the time does not. Digging deeper it seems that occasionally if and only if the file is opened by another user and java is trying to overwrite the file an AccessDenied Exception is thrown and the file is deleted.</p>
  
  <p>I believe this must be a bug in setWritable() or Files.copy (or a combination) as the file should not be deleted in any case and isWritable() returns true every time. I have tried other methods for setting/UN-setting read only permissions and have come up empty.  The current work around that I have in place simply catches the exception and loops until the file is deleted and a fresh copy is in place. This works but is really a hack so if anyone has any better solutions/suggestions I welcome them.</p>