Java - RandomAccessFile

This class is used for reading and writing to random access file. A random access file behaves like a large array of bytes. There is a cursor implied to the array called file pointer, by moving the cursor we do the read write operations. If end-of-file is reached before the desired number of byte has been read than EOFException is thrown. It is a type of IOException.

Constructor

Constructor	Description
RandomAccessFile(File file, String mode)	Creates a random access file stream to read from, and optionally to write to, the file specified by the File argument.
RandomAccessFile(String name, String mode)	Creates a random access file stream to read from, and optionally to write to, a file with the specified name.

Method

Modifier and Type	Method	Method
void	close()	It closes this random access file stream and releases any system resources associated with the stream.
FileChannel	getChannel()	It returns the unique FileChannel object associated with this file.
int	readInt()	It reads a signed 32-bit integer from this file.
String	readUTF()	It reads in a string from this file.
void	seek(long pos)	It sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs.
void	writeDouble(double v)	It converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an eight-byte quantity, high byte first.
void	writeFloat(float v)	It converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a four-byte quantity, high byte first.
void	write(int b)	It writes the specified byte to this file.
int	read()	It reads a byte of data from this file.
long	length()	It returns the length of this file.
void	seek(long pos)	It sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs.

Example

import java.io.IOException;
import java.io.RandomAccessFile;

public class RandomAccessFileExample {
	static final String FILEPATH ="myFile.TXT";
	public static void main(String[] args) {
		try {
			System.out.println(new String(readFromFile(FILEPATH, 0, 18)));
			writeToFile(FILEPATH, "I love my country and my people", 31);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	private static byte[] readFromFile(String filePath, int position, int size)
			throws IOException {
		RandomAccessFile file = new RandomAccessFile(filePath, "r");
		file.seek(position);
		byte[] bytes = new byte[size];
		file.read(bytes);
		file.close();
		return bytes;
	}
	private static void writeToFile(String filePath, String data, int position)
			throws IOException {
		RandomAccessFile file = new RandomAccessFile(filePath, "rw");
		file.seek(position);
		file.write(data.getBytes());
		file.close();
	}
}

The myFile.TXT contains text "This class is used for reading and writing to random access file."

after running the program it will contains

This class is used for reading I love my country and my peoplele.

Next Topicjava.util.Scanner

← prev next →