JavaLock.java

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.channels.OverlappingFileLockException;

public class FileLockingExample {
    public static void main(String[] args) {
        File file = new File("locked_file.txt");
        try {
            file.createNewFile();
        } catch (IOException e) {
            System.err.println("Error creating file: " + e.getMessage());
            return;
        }
        try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
             FileChannel channel = randomAccessFile.getChannel()) {

            System.out.println("Attempting to acquire lock on: " + file.getAbsolutePath());
            FileLock lock = null;
            try {
                lock = channel.lock(); // This line attempts to acquire the lock.
                if (lock != null) {
                    System.out.println("Lock acquired!\n Performing ops on the locked file...");
                    Thread.sleep(5000); // Simulate some work.
                    System.out.println("Finished file operations.");
                }
            } catch (OverlappingFileLockException e) {
                System.err.println("File is already locked by another process or thread.");
            } catch (IOException | InterruptedException e) {
                 System.err.println("Error during lock operation: " + e.getMessage());
            } finally {
                 if(lock != null) {
                     System.out.println("Attempting to release Lock.");
                     lock.release();
                     System.out.println("Lock released.");
                 }
            }
        } catch (IOException e) {
            System.err.println("Error accessing file: " + e.getMessage());
        }
    }
}