}

  /**
   * Guaranteed to throw an exception and leave the map unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull
  public final Entry<K, V> pollFirstEntry() {
    throw new UnsupportedOperationException();
  }

    return FS.getRootDirectories().iterator().next();
  }

  private Path tempDir;

  @Override
  protected void setUp() throws Exception {
    tempDir = Files.createTempDirectory("MoreFilesTest");
  }

  @Override
  protected void tearDown() throws Exception {
    if (tempDir != null) {
      // delete tempDir and its contents
      Files.walkFileTree(
          tempDir,

   *
   * @throws NoSuchFileException if the file does not exist <i>(optional specific exception)</i>
   * @throws NotDirectoryException if the file could not be opened because it is not a directory
   *     <i>(optional specific exception)</i>
   * @throws IOException if an I/O error occurs
   */
  public static ImmutableList<Path> listFiles(Path dir) throws IOException {

   *
   * @throws NoSuchFileException if the file does not exist <i>(optional specific exception)</i>
   * @throws NotDirectoryException if the file could not be opened because it is not a directory
   *     <i>(optional specific exception)</i>
   * @throws IOException if an I/O error occurs
   */
  public static ImmutableList<Path> listFiles(Path dir) throws IOException {

  }

  public void testCopyTo_appendable() throws IOException {
    StringBuilder builder = new StringBuilder();

    assertEquals(STRING.length(), source.copyTo(builder));
    assertTrue(source.wasStreamOpened() && source.wasStreamClosed());

    assertEquals(STRING, builder.toString());
  }

  public void testCopyTo_charSink() throws IOException {
    TestCharSink sink = new TestCharSink();

   * it does.
   *
   * @throws IOException if an I/O error occurs while reading from this source or if {@code
   *     processor} throws an {@code IOException}
   * @since 16.0
   */
  @CanIgnoreReturnValue // some processors won't return a useful result
  @ParametricNullness
  public <T extends @Nullable Object> T readLines(LineProcessor<T> processor) throws IOException {
    checkNotNull(processor);

  final ImmutableSet<V> createValues() {
    throw new AssertionError("should never be called");
  }

  /**
   * Guaranteed to throw an exception and leave the bimap unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull

   * writer each time it is called.
   *
   * <p>The caller is responsible for ensuring that the returned writer is closed.
   *
   * @throws IOException if an I/O error occurs while opening the writer
   */
  public abstract Writer openStream() throws IOException;

  /**
   * Opens a new buffered {@link Writer} for writing to this sink. The returned stream is not

    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull

  @DoNotCall("Always throws UnsupportedOperationException")
  public final void putCoalescing(Range<K> range, V value) {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override