OnJava8-Examples/io/FileLocking.java

// io/FileLocking.java
// <20>2015 MindView LLC: see Copyright.txt
import java.nio.channels.*;
import java.util.concurrent.*;
import java.io.*;

public class FileLocking {
  public static void main(String[] args) throws Exception {
    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");
      }
    }
  }
}
/* Output:
Locked File
Released Lock
*/