FULL PRODUCT VERSION :
ALIPLR2508:~ user$ java -version
Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF16
??java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
macOS High Sierra
version 10.13.1

EXTRA RELEVANT SYSTEM CONFIGURATION :
MacBook Pro (2016 model)
Processor 2GHz intel core i5
Memory 8 GB 1867 MHz LPDDR3
Graphics Intel Irish Graphics 540 1536 MB

A DESCRIPTION OF THE PROBLEM :
I am trying to access and obtain lock on a file on a shared location in my network.
But the tryLock method on FileChannel fails to obtain lock giving error message "Operation not supported".

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile and run the below program in any MAC environment and try to access a shared file on network.
Note: Please edit the "filePath" variable to a valid file path on shared network.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
We should see the following output:
Lock object obtained
Lock released successfully
ACTUAL -
java.io.IOException: Operation not supported
at sun.nio.ch.FileDispatcherImpl.lock0(Native Method)
at sun.nio.ch.FileDispatcherImpl.lock(FileDispatcherImpl.java:90)
at sun.nio.ch.FileChannelImpl.tryLock(FileChannelImpl.java:1115)
at com.file.lock.FileLock.main(FileLock.java:24)
Operation not supported
Failed to obtain lock

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.util.Scanner;

public class FileLock {

private static RandomAccessFile raf = null;
private static java.nio.channels.FileLock lock = null;
private static FileChannel channel = null;
private static File file = null;

public static void main(String[] args) {

// path for mac which fails to lock
String filePath1 = "/Volumes/accion/Wonderful Life Demo V5.msd";
String filePath = "\\\\ALIPL0343\\Users\\AL1398\\MMData\\MM Scheduling\\Examples\\Wonderful Life Demo V5.msd";
file = new File(filePath);
try {
raf = new RandomAccessFile(file, file.canWrite() ? "rw" : "r");
channel = raf.getChannel();
// This method fails on MAC and works fine on windows
lock = channel.tryLock(0L, Long.MAX_VALUE, file.canWrite() ? false : true);
} catch (FileNotFoundException e1) {
e1.printStackTrace();
System.out.println(e1.getMessage());
} catch (IOException e) {
e.printStackTrace();
System.out.println(e.getMessage());
}

if (null == lock) {
System.out.println("Failed to obtain lock");
} else {
try {
Scanner scan = new Scanner(file);
System.out.println("Lock object obtained");
while (scan.hasNextLine()) {
System.out.println(scan.nextLine());
}
scan.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} finally {
try {
lock.release();
channel.close();
raf.close();
System.out.println("Lock released successfully");
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

}
---------- END SOURCE ----------