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Java Random Access Files

The RandomAccessFile class in Java allows you to read from and write to a file at any position. It supports both sequential and random access, making it suitable for tasks like updating records in a file.

1. Creating a RandomAccessFile

Instantiate a RandomAccessFile object by specifying the file and the mode ("r" for read-only, "rw" for read and write).

Example:

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

public class RandomAccessFileExample {
    public static void main(String[] args) {
        try {
            RandomAccessFile raf = new RandomAccessFile("data.txt", "rw");
            // Use raf to read and write
            raf.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2. Reading Data

You can read data using methods like readInt(), readLine(), readUTF(), etc.

Example: Reading from a Specific Position

raf.seek(100); // Move the file pointer to position 100
int data = raf.readInt();

3. Writing Data

Write data using methods like writeInt(), writeUTF(), etc.

Example: Writing at a Specific Position

raf.seek(200); // Move the file pointer to position 200
raf.writeUTF("Hello, World!");

4. Getting the File Pointer

You can get the current position of the file pointer using getFilePointer().

Example:

long position = raf.getFilePointer();
System.out.println("Current file pointer position: " + position);

5. Key Takeaways

  • RandomAccessFile allows reading and writing at arbitrary positions.
  • Supports both sequential and random access.
  • Useful for applications like databases and file-based records.
  • Always close the file to release resources.
  • Be mindful of data types and file formats when using random access.
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