FileInputStream getFD() Method in Java with Examples

Last Updated : 01 Dec, 2021

Java.io.FileInputStream.getFD() method is a part of Java.io.FileInputStream class. This method will return the FileDescriptor object associated with the file input stream.

getFD() method is declared as final that means getFD() cannot be overridden in the subclasses
FileDescriptor object that we will get using getFD() method will represent the connection to the actual file in the file system
getFD() method might throw IOException.

Syntax:

public final FileDescriptor getFD() throws IOException

Return Type: getFD() method will return the instance of FileDescriptor associated with this FileInputStream.

Exception: getFD() method might throw IOException if any Input/output exception raises.

How to invoke getFD() method?

Step 1: First, we have to create an instance of Java.io.FileInputStream class

FileInputStream  fileInputStream =new FileInputStream("tmp.txt");

Step 2: To get the instance of FileDescriptor associated with this fileInputStream, we will invoke the getFD() method

FileDescriptor fileDescriptor =fileInputStream.getFD();

Example: Java Program to get an instance of FileDescriptor and then to check it is valid or not

In the below program, we will

use Java.io.FileInputStream.getFD() method to get the object of FileDescriptor
use FileDescriptor valid() method to check if the instance of the file descriptor is valid or not

Java

// Java Program to get an instance
// of FileDescriptor and then to
// check it is valid or not

import java.io.*;
class GFG {
    public static void main(String[] args)
    {
        try {
            // create instance of FileInputStream class
            // user should change name of the file
            FileInputStream fileInputStream
                = new FileInputStream(
                    "C://geeksforgeeks//tmp.txt");

            // if the specified file does not exist
            if (fileInputStream == null) {
                System.out.println(
                    "Cannot find the specified file");
                return;
            }

            // to get the object of FileDescriptor for
            // this specified fileInputStream
            FileDescriptor fileDescriptor
                = fileInputStream.getFD();

            // check if the fileDescriptor is valid or not
            // using it's valid method
            // valid() will return true if valid else false
            System.out.println("Is FileDescriptor valid : "
                               + fileDescriptor.valid());
          
            // will close the file input stream and releases
            // any system resources associated with the
            // stream.
            fileInputStream.close();
        }
        catch (Exception exception) {
            System.out.println(exception.getMessage());
        }
    }
}