assertEquals("gz", Files.getFileExtension("blah.tar.gz"));
    assertEquals("", Files.getFileExtension("/"));
    assertEquals("", Files.getFileExtension("."));
    assertEquals("", Files.getFileExtension(".."));
    assertEquals("", Files.getFileExtension("..."));
    assertEquals("", Files.getFileExtension("blah"));
    assertEquals("", Files.getFileExtension("blah."));
    assertEquals("", Files.getFileExtension(".blah."));

        FileOutputStream out = new FileOutputStream(file);
        try {
          out.write(initialBytes);
        } finally {
          out.close();
        }
        return Files.asByteSink(file, FileWriteMode.APPEND);
      }
      return Files.asByteSink(file);
    }

    @Override
    public byte[] getExpected(byte[] bytes) {
      if (initialBytes == null) {
        return checkNotNull(bytes);
      } else {

/**
 * Unit test for {@link Files#createTempDir}.
 *
 * @author Chris Nokleberg
 */

@SuppressWarnings("deprecation") // tests of a deprecated method
public class FilesCreateTempDirTest extends TestCase {
  public void testCreateTempDir() throws IOException {
    if (JAVA_IO_TMPDIR.value().equals("/sdcard")) {
      assertThrows(IllegalStateException.class, Files::createTempDir);
      return;
    }

    util.concurrent tests under Guava.

    The problem is that GWT responds poorly to two .gwt.xml files in the same
    Java package; see https://goo.gl/pRV3Yn for details.

    The summary is that it ignores one file in favor of the other.
    util.concurrent, like nearly all our packages, has two .gwt.xml files: one
    for prod and one for tests. However, unlike our other packages, as of this

      (a) You must give any other recipients of the Work or
          Derivative Works a copy of this License; and

      (b) You must cause any modified files to carry prominent notices
          stating that You changed the files; and

      (c) You must retain, in the Source form of any Derivative Works
          that You distribute, all copyright, patent, trademark, and

 * nullness annotations in particular will outweigh the costs. (And it's worth noting that we have
 * released multiple ListenableFuture.class files that are not byte-for-byte compatible even from
 * the beginning, thanks to using different `-source -target` values for compiling our `-jre` and
 * `-android` "flavors.")
 *

 *
 * <p>{@link java.nio.file.Path} users will find similar utilities in {@link MoreFiles} and the
 * JDK's {@link java.nio.file.Files} class.
 *
 * @author Chris Nokleberg
 * @author Colin Decker
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class Files {

  private Files() {}

  /**

        // Permissions needed by the junit test harness
        new RuntimePermission("accessDeclaredMembers"),
        new PropertyPermission("*", "read"),
        new java.io.FilePermission("<<ALL FILES>>", "read"));
  }

  /** Sleeps until the given time has elapsed. Throws AssertionFailedError if interrupted. */
  void sleep(long millis) {
    try {
      delay(millis);
    } catch (InterruptedException ie) {

    assertEquals("gz", Files.getFileExtension("blah.tar.gz"));
    assertEquals("", Files.getFileExtension("/"));
    assertEquals("", Files.getFileExtension("."));
    assertEquals("", Files.getFileExtension(".."));
    assertEquals("", Files.getFileExtension("..."));
    assertEquals("", Files.getFileExtension("blah"));
    assertEquals("", Files.getFileExtension("blah."));
    assertEquals("", Files.getFileExtension(".blah."));

                .build());
    Files.createDirectories(fs.getPath("dir/b/i/j/l"));
    Files.createFile(fs.getPath("dir/a"));
    Files.createFile(fs.getPath("dir/c"));
    Files.createSymbolicLink(fs.getPath("dir/d"), fs.getPath("b/i"));
    Files.createDirectory(fs.getPath("dir/e"));
    Files.createSymbolicLink(fs.getPath("dir/f"), fs.getPath("/dontdelete"));
    Files.createFile(fs.getPath("dir/b/g"));