RAF method....

[sonir shah]

import java.io.*;
    public class T022
    {    
        public static void main(String args[]) throws IOException
        {
            File f = new File("test.dat");
            System.out.print(f.length() + " ");            
            RandomAccessFile ra = new RandomAccessFile(f, "rw");
            ra.write(10);
            System.out.println(ra.length());
        }
    }

The output is : 0 1
I am wondering from where did this 0 1 come from..Any explainations ??
Sonir

[Rob Ross]

System.out.print(f.length + " ");
This prints the length of the file f in bytes. Since you just created a brand new file name, the file is empty and is zero bytes long. That's where the first 0 comes from.
Then you write a byte to the file:
ra.write(10);
And you print the new length:
System.out.println(ra.length());
Since you just wrote 1 byte, it's now 1 byte long. That's where the 1 comes from.
Rob

[sonir shah]

Rob
How do you know that write() method will write only 1 byte ..
??
Sonir

[Rob Ross]

Because the JavaDoc for RandomAccessFile tells me so.
public void write(int b)
throws IOException
Writes the specified byte to this file. The write starts at the current file pointer.
JavaDoc is indespensible! It's the offial documentation for all the Java class libraries.

Rob

[sonir shah]

Ok Rob
Will it always write 1, or will it see what is passed into the write() method's argument?..

Sonir

[Junilu Lacar]

Sonir,
The program will always write 1 byte. It does not always write 1. The actual value written will be the 8 low order bits (the rightmost bits) of the value passed to write(). You need to dig into the JavaDocs a little to find this information (I'll leave this to you as an exercise -- which BTW involves mainly just clicking on links and reading).
The program outputs 1 because it is printing the value of ra.length(), not the actual value written.