Java FileDescriptor

FileDescriptor class serves as an handle to the underlying machine-specific structure representing an open file, an open socket, or another source or sink of bytes. The handle can be err, in or out.

The FileDescriptor class is used to create a FileInputStream or FileOutputStream to contain it.

Field

Modifier	Type	Field	Description
static	FileDescriptor	err	A handle to the standard error stream.
static	FileDescriptor	in	A handle to the standard input stream.
static	FileDescriptor	out	A handle to the standard output stream.

Constructors

Constructor	Description
FileDescriptor()	Constructs an (invalid) FileDescriptor object.

Method

Modifier and Type	Method	Description
void	sync()	It force all system buffers to synchronize with the underlying device.
boolean	valid()	It tests if this file descriptor object is valid.

Java FileDescriptor Example

import java.io.*;
public class FileDescriptorExample {
	public static void main(String[] args) {
		FileDescriptor fd = null;
		byte[] b = { 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58 };
		try  {
			FileOutputStream fos = new FileOutputStream("Record.txt");
			FileInputStream fis = new FileInputStream("Record.txt");
			fd = fos.getFD();
			fos.write(b);
			fos.flush();
			fd.sync();// confirms data to be written to the disk
			int value = 0;
			// for every available bytes
			while ((value = fis.read()) != -1) {
				char c = (char) value;// converts bytes to char
				System.out.print(c);
			}
			System.out.println("\nSync() successfully executed!!");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output:

0123456789:
Sync() successfully executed!!

Record.txt:

0123456789:

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