// newio/FileLocking.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.nio.channels.*;
import java.util.concurrent.*;
import java.io.*;

public class FileLocking {
  public static void main(String[] args) {
    try(
      FileOutputStream fos =
        new FileOutputStream("file.txt");
      FileLock fl = fos.getChannel().tryLock()
    ) {
      if(fl != null) {
        System.out.println("Locked File");
        TimeUnit.MILLISECONDS.sleep(100);
        fl.release();
        System.out.println("Released Lock");
      }
    } catch(IOException | InterruptedException e) {
      throw new RuntimeException(e);
    }
  }
}
/* Output:
Locked File
Released Lock
*/