FULL PRODUCT VERSION :
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b18)
Java HotSpot(TM) 64-Bit Server VM (build 25.66-b18, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.10240]

A DESCRIPTION OF THE PROBLEM :
Using filestream.flush - data is not physically written to disc

ADDITIONAL REGRESSION INFORMATION:
I'd guess the problem is related to running on Windows 10 - is this platform not supported yet ?

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :

Build the code example in the "source code" box below.
Check you have a c:\temp directory created.
Run the code.
Open a dos window, cd c:\temp and run the "dir" command a number of times
Check the size of the file TestFile.log, it should slowly increase.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -

I'd expect to see the file size gradually increasing, however it stays at zero until the program is interrupted and exits.
ACTUAL -
File size stays at zero, confirmed with "dir" command in dos window

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package any.old.package;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

public class TestFileAccess {

public static void main(String[] args) throws InterruptedException, IOException {

File f = new File("C:\\TEMP\\TestFile.log");
FileWriter out = new FileWriter (f);
for (;;) {
out.write("Hello, World");
out.flush();
Thread.sleep(10);
}
}
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
close the file writer stream and reopen it with append mode.