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public void processFile_nce(String filename){
  // Identify a file by its path
  Path file1 = Paths.get(filename);
 
  // Open the file for writing
  try (BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(Files.newOutputStream(file1)))) {
    // Write to file...
  } catch (IOException e) {
    // Handle error
  } 
  
  // Close the file
  
  /*
   * A race condition here allows for an attacker to switch
   * out the file for another
   */

  // Reopen the file for reading
  Path file2 = Paths.get(filename);
    
  try (BufferedReader br = new BufferedReader(new InputStreamReader(Files.newInputStream(file2)))) {
    String line;
    while ((line = br.readLine()) != null) {
      System.out.println(line);
    }
  } catch (IOException e) {
    // Handle error
  } 
}

public void sameFile_nceprocessFile(String filename){
  // Identify a file by its path
  Path file1 = Paths.get(filename);
  
  // Open the file for writing
  try(BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(Files.newOutputStream(file1)))) {
    // Write to file
  } catch (IOException e) {
    // Handle error
  } 
  
  // ...
  // Reopen the file for reading
  Path file2 = Paths.get(filename);
  if (!Files.isSameFile(file1, file2)) {
    System.out.println("File tampered with");
    // Handle error
  }
  
  try(BufferedReader br = new BufferedReader(new InputStreamReader(Files.newInputStream(file2)))) { 
    String line;
    while ((line = br.readLine()) != null) {
      System.out.println(line);
    }
  } catch (IOException e) {
    // Handle error
  } 
}

public void sameFile_csprocessFile(String filename) throws IOException{
  // Identify a file by its path
  Path file1 = Paths.get(filename);
  BasicFileAttributes attr1 = Files.readAttributes(file1, BasicFileAttributes.class);
  FileTime creation1 = attr1.creationTime();
  FileTime modified1 = attr1.lastModifiedTime();

  // Open the file for writing
  try (BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(Files.newOutputStream(file1)))) {
    // Write to file...
  } catch (IOException e) {
    // Handle error
  } 
  
  // Reopen the file for reading
  Path file2 = Paths.get(filename);
  BasicFileAttributes attr2 = Files.readAttributes(file2, BasicFileAttributes.class);
  FileTime creation2 = attr2.creationTime();
  FileTime modified2 = attr2.lastModifiedTime();
  if ( (!creation1.equals(creation2)) || (!modified1.equals(modified2)) ) {
    System.out.println("File tampered with");
    // Handle error
  }
  
  try(BufferedReader br = new BufferedReader( new InputStreamReader(Files.newInputStream(file2)))){
    String line;
    while ((line = br.readLine()) != null) {
      System.out.println(line);
    }
  } catch (IOException e) {
    // Handle error
  } 
}

public void filekey_csprocessFile(String filename) throws IOException{
  // Identify a file by its path
  Path file1 = Paths.get(filename);
  BasicFileAttributes attr1 = Files.readAttributes(file1, BasicFileAttributes.class);
  Object key1 = attr1.fileKey();
  // Open the file for writing
  try(BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(Files.newOutputStream(file1)))) {
    // Write to file
  } catch (IOException e) {
    // Handle error
  } 
  
  // Reopen the file for reading
  Path file2 = Paths.get(filename);
  BasicFileAttributes attr2 = Files.readAttributes(file2, BasicFileAttributes.class);
  Object key2 = attr2.fileKey();

  if ( !key1.equals(key2) ) {
    System.out.println("File tampered with");
    // handle error
  }

  try(BufferedReader br = new BufferedReader(new InputStreamReader(Files.newInputStream(file2)))) {
    String line;
    while ((line = br.readLine()) != null) {
      System.out.println(line);
    }
  } catch (IOException e) {
    // Handle error
  } 
} 

public void randomAccess_csprocessFile(String filename) throws IOException{
  // Identify a file by its path
  RandomAccessFile file = new RandomAccessFile( filename, "rw");

  // Write to file...

  // Go back to beginning and read contents
  file.seek(0);
  try {
    while (true) {
      String s = file.readUTF();
      System.out.print(s);
    }
  } catch (EOFException x) {
    // Ignore, this breaks out of while loop
  }
  br.close();
}