FileInputStream getFD() Method in Java with Examples

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());
        }
    }
}

Output:

Is FileDescriptor valid : true

tmp.txt

Note: The programs will run on an online IDE. Please use an offline IDE and change the Name of the file according to your need.