Random access files in Java

A random-access file is a file in which the user or programmer can read and write data to the file at any location (hence the name random) simultaneously. A random-access file behaves like a large array of bytes. To navigate through the file, there is a file pointer which can be moved to the desired location.
 

The RandomAccessFile in Java is a pre-defined class that belongs to java.io package which allows the programmers to work with random access files. While moving the file pointer, if end of file is reached, it throws an EOFException. The constructors in RandomAccessFile class are given below:

Some of the methods available in the RandomAccessFile class are given below:

Following Java program demonstrates reading and writing to a random-access file using the RandomAccessFile class:

import java.io.*;
public class RandomAccess
{
	public static void main(String[] args) throws Exception
	{
		RandomAccessFile raf = new RandomAccessFile("rand.txt", "rw");
		int size = (int)raf.length();
		System.out.println("File length = " + size + " bytes.");
		
		//Code for reading data from the file
		raf.seek(10);
		byte[] data = new byte[size];
		raf.read(data);
		System.out.println("Content in the file = " + new String(data));
		
		//Code for writing data to the file
		raf.seek(size);
		String s = "New piece of text.";
		raf.write(s.getBytes());
		raf.close();
	}
}

Output for the above program is:

File length = 30 bytes.
Content in the file = sample line of text.

When you open rand.txt and see the content, it will be:

This is a sample line of text.New piece of text.

For more information, visit the following links:

• Java – RandomAccessFile

Suryateja Pericherla

Suryateja Pericherla, at present is a Research Scholar (full-time Ph.D.) in the Dept. of Computer Science & Systems Engineering at Andhra University, Visakhapatnam. Previously worked as an Associate Professor in the Dept. of CSE at Vishnu Institute of Technology, India.

He has 11+ years of teaching experience and is an individual researcher whose research interests are Cloud Computing, Internet of Things, Computer Security, Network Security and Blockchain.

He is a member of professional societies like IEEE, ACM, CSI and ISCA. He published several research papers which are indexed by SCIE, WoS, Scopus, Springer and others.