here a bug found in JDK 7.45 on Windows. I'm running Groovy 2.2.1 on the top of the JVM.

JavaPathDotTest.java

import org.junit.Test

import java.nio.file.FileVisitResult
import java.nio.file.Path
import java.nio.file.Paths

/***
 * Bug with directory starting by '.'
 * 
 * Here is test to reproduce this issue.
 *  - Windows 7 / 64 bits
 *  - JVM 7.45
 */
class JavaBug
{

  @Test
  void fileWithDot()
  {
    Path path = Paths.get("path/to/.git");
    
    // This test should fail because the directory name is: .git
    assert !path.fileName.startsWith(".");
    
    // This test passed when the directory name is converted to String
    assert path.fileName.toString().startsWith(".");
  }
}