lock.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"syscall"
)

func main() {
	var err error
	mode := syscall.O_CREAT | syscall.O_RDWR
	lockFile, err := os.OpenFile("test.lock", mode, 0666)
	if err != nil {
		fmt.Print("failed to open lockfile")
	}

	lock := syscall.Flock_t{
		Start:  0,
		Len:    0,
		Type:   syscall.F_WRLCK,
		Whence: io.SeekStart,
	}

	err = syscall.FcntlFlock(lockFile.Fd(), syscall.F_SETLK, &lock)

	if err != nil {
		fmt.Print("failed to acquire lock")
	} else {
		fmt.Print("Press 'Enter' to continue...")
		bufio.NewReader(os.Stdin).ReadBytes('\n')
	}
}

lock.java

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.channels.WritableByteChannel;
import java.nio.file.Files;
import java.io.Console;

public class lock {
  public static void main(final String[] args) throws Exception {
    // Read from file
    Console c = System.console();
    final File inputFile = new File("test.lock");
    FileChannel fc;
    FileLock fl;
    try (final RandomAccessFile raf = new RandomAccessFile(inputFile, "rw")) {
      fc = raf.getChannel();
    c.format("\nPress ENTER to proceed.\n");
    c.readLine();
      fl = fc.tryLock();
    c.format("\nPress ENTER to proceed.\n");
    c.readLine();
      if (fl == null) {
          System.out.println("failed to acquire lock");
        // Failed to acquire lock
      } 
    }

  }

}