FULL PRODUCT VERSION :
java version "1.8.0_152"
Java(TM) SE Runtime Environment (build 1.8.0_152-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.152-b16, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
macOS High Sierra (10.13.3)

A DESCRIPTION OF THE PROBLEM :
The following test demonstrates the bug. I believe this bug is also in JDK 7, but I have not confirmed.



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
I ran the attached test case, which demonstrates that I cannot move non-empty directory across file system. If the source directory is empty, then the move succeeds.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expected test to succeed
ACTUAL -
java.nio.file.DirectoryNotEmptyException: mySrc

at sun.nio.fs.UnixFileSystemProvider.implDelete(UnixFileSystemProvider.java:242)
at sun.nio.fs.AbstractFileSystemProvider.delete(AbstractFileSystemProvider.java:103)
at java.nio.file.Files.delete(Files.java:1126)
at java.nio.file.CopyMoveHelper.moveToForeignTarget(CopyMoveHelper.java:158)
at java.nio.file.Files.move(Files.java:1398)
at test.file.move.MoveDirectoryAcrossFileSystems.test(MoveDirectoryAcrossFileSystems.java:26)
...

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package test.file.move;

import com.google.common.jimfs.Configuration;
import com.google.common.jimfs.Jimfs;
import org.apache.commons.io.FileUtils;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Test;

import java.nio.channels.FileChannel;
import java.nio.file.*;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class MoveDirectoryAcrossFileSystems {
  Path src = Paths.get("mySrc");

  FileSystem fs = Jimfs.newFileSystem(Configuration.unix());
  Path dest = fs.getPath("/dest");

  @Test
  public void test() throws Exception {
    Files.createDirectory(src);
    FileChannel.open(src.resolve("file"), StandardOpenOption.WRITE, StandardOpenOption.CREATE_NEW).close();
    assertEquals(dest, Files.move(src, dest));

    assertFalse(Files.exists(src));
    assertTrue(Files.exists(dest.resolve("file")));
  }

  @AfterEach
  public void cleanup() {
    FileUtils.deleteQuietly(src.toFile());
    FileUtils.deleteQuietly(dest.toFile());
  }
}

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

CUSTOMER SUBMITTED WORKAROUND :
I have not found one, but I would expect to be able to code a move across file system manually.