Introduction
Java.io FileDescriptor class is used to access the file or input /output resources. The class instances serve as a machine-specific structure, which represent an open file, socket, another source or sink of bytes.
Mainly the file descriptor is used to create a File I/O stream to hold it. Any application could not create their file descriptors by own.
Declaration
Java.io FileDescriptor class is declared as shown below:
public final class FileDescriptor extends object
Fields
Java.io FileDescriptorclass fields are as follows:
- static FileDescriptor i: This field is used to hold the quality input stream.
- static FileDescriptor o: This field is used to hold the quality output stream.
- static FileDescriptor er: This field is used to hold the quality error stream.
Table
| Constructor | Description |
|---|---|
| FileDescriptor() | This constructor constructs an Java.io FileDescriptor object (invalid). |
Table
| Method | Description |
|---|---|
| void sync() | This method functions with the underlying device all system buffers to synchronize. |
| boolean valid() | This method checks that the file descriptor object is valid or not. |
Description
From the following classes methods are inherited to Java.io FileDescriptor
- Java.io.Object
Examples
Usage of boolean valid() method.
[c]import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.IOException;
public class FileDescriptor
{
public static void main(String[] args) throws IOException
{
FileInputStream fi = null;
FileDescriptor fd = null;
boolean bl = false;
try{
// creating input stream
fi = new FileInputStream("c:/java test.txt");
// It gets file descriptor
fd = fi.getFD();
// testing the validity of file descriptor object
bl = fd.valid();
// print the the file discriptor is valid or not
System.out.print("Is file descriptor valid? "+bl);
}catch(Exception e)
{
// if any error occurs
e.printStackTrace();
}finally
{
// Releases all systems resources
if(fi!=null)
fi.close();
}
}
}[/c]
Output
The result is as follows.
[c]Is file descriptor is valid? true [/c]
Key Points
- Java.io.FileDescriptor class is used to access the file or input/output resources.
- The class instances serve as a machine-specific structure, which represent an open file, socket, another source or sink of bytes.
- Mainly the file descriptor is used to create a File I/O stream to hold it.
- Any application could not create their file descriptors by own.