java.nio.file.SimpleFileVisitor Class in Java

The java.nio.file.SimpleFileVisitor Class is used to visit all the files in a directory and to re-throw I/O exceptions whenever an I/O error occurs.

Class declaration :

public class SimpleFileVisitor<T>
extends Object
implements FileVisitor<T>

Constructor:

• protected SimpleFileVIsitor(): Creates a new object of SimpleFileVisitor class.

Method:

1.public FileVisitResult preVisitDirectory(T directory, BasicFileAttributes attributes): This method is invoked for this directory before the entries in the are visited. This method returns to CONTINUE unless overridden.

Parameters:
directory- reference to this directory.
attributes- attributes of this directory.

Returns: the file visit result.

Throws: I/O Exception.

2.public FileVisitResult postVisitDirectory(T directory, IOException e): This method is invoked for this directory after the entries in the are visited. This method returns to CONTINUE unless overridden.

Parameters:
directory- reference to this directory.
e- NULL if there is no error in this directory's 
iteration,else the I/O exception.

Returns: the file visit result.

Throws: I/O Exception.

3.public FileVisitResult visitFile(T file, BasicFileAttributes attributes): This method is invoked for this file before in a directory. This method returns to CONTINUE unless overridden.

Parameters:
file- reference to this file.
attributes- attributes of this file.

Returns: the file visit result.

Throws: I/O Exception 

4.public FileVisitResult visitFileFailed(T file, IOException exception): This method is invoked for a file that could not be visited. This method re-throws the I/O exception unless overridden. This was the exception that prevented the file from being visited.

Parameters:
file - reference to this file.
exc - exception that prevented the file from being visited.

Returns: the file visit result.

Throws: I/O Exception 

// Java program to demonstrate working of simpleFileVisitor
// class

import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.*;

public class FileVisitorDemo
    extends SimpleFileVisitor<Path> {
    public FileVisitResult
    visitFile(Path file, BasicFileAttributes atts)
        throws IOException
    {
        if (file.getFileName().toString().endsWith(
                ".txt")) { // delete files ending with .txt
            Files.delete(file);
        } // return result of the operation
        return FileVisitResult.CONTINUE;
    }
    // Method to print message if file visit was not
    // successful
    public FileVisitResult visitFileFailed(Path file,
                                           IOException e)
        throws IOException
    {
        System.err.println("File could not be visited");
        return FileVisitResult.CONTINUE;
    }
    public static void main(String args[]) throws Exception
    {
        FileVisitorDemo visitor = new FileVisitorDemo();
        try {
            // visiting all files at
            // "/Users/abhinavjain194/desktop/visit"
            Files.walkFileTree(
                Paths.get(
                    "/Users/abhinavjain194/desktop/visit"),
                visitor);
        }
        catch (Exception e) { // printing error if occurred
            System.err.print(e.toString());
        }
    }
}

Before running the program

After running the program