FULL PRODUCT VERSION :
java version "1.8.0_112"
Java(TM) SE Runtime Environment (build 1.8.0_112-b15)
Java HotSpot(TM) Client VM (build 25.112-b15, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
A logical error in java.nio.file.FileTreeWalker:

reaching the maxDepth and the current entry being a directory causes FileVisitor.visitFile to be called instead of the directory-methods.

The problematic code (starting at line 285):

        // at maximum depth or file is not a directory
        int depth = stack.size();
        if (depth >= maxDepth || !attrs.isDirectory()) {
            return new Event(EventType.ENTRY, entry, attrs);
        }


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
in Files.walkFileTree with a max-depth and having only directories in maxDepth's subfolders.


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.io.IOException;
import java.io.PrintStream;
import java.io.UncheckedIOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.HashSet;

public class TestFTW {

  static void testFileTreeWalker() {
    try {
      final PrintStream verbose = System.out;
      verbose.println(
        "java version " + System.getProperty("java.version", "unknown"));
      Files.createDirectories(Paths.get(".\\subtest\\subtest1"));
      final Path start = Paths.get(".\\subtest");
      Files.walkFileTree(start, new HashSet<>(), 1,
        new SimpleFileVisitor<Path>() {
          @Override
          public FileVisitResult preVisitDirectory(final Path dir,
            final BasicFileAttributes attrs) throws IOException {
            verbose.println("preVisitDirectory: " + dir);
            if (dir.equals(start))
              return FileVisitResult.CONTINUE;
            verbose.println("preVisitDirectory: doing something");
            return FileVisitResult.CONTINUE;
          }

          @Override
          public FileVisitResult postVisitDirectory(final Path dir,
            final IOException exc) throws IOException {
            verbose.println("postVisitDirectory: " + dir);
            if (dir.equals(start))
              return FileVisitResult.CONTINUE;
            verbose.println("postVisitDirectory: doing something");
            return FileVisitResult.CONTINUE;
          }

          @Override
          public FileVisitResult visitFile(final Path file,
            final BasicFileAttributes attrs) throws IOException {
            verbose.println("visitFile: " + file);
            if (Files.isDirectory(file)) {
              throw new IllegalStateException("java error in visitFile: " + file
                + " is directory not a regular file - attrs.isDirectory() = "
                + attrs.isDirectory() + ", attrs.isRegularFile() = "
                + attrs.isRegularFile());
            }
            verbose.println("visitFile: doing something");
            return FileVisitResult.CONTINUE;
          }

          @Override
          public FileVisitResult visitFileFailed(final Path file,
            final IOException exc) throws IOException {
            throw exc;
          }
        });
    } catch (final IOException e) {
      throw new UncheckedIOException(e);
    }
  }

  public static void main(final String[] args) {
    testFileTreeWalker();
  }
}

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

CUSTOMER SUBMITTED WORKAROUND :
All FileVisitors have to check the attributes in FileVisitor.visitFile().