@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class MultiInputStream extends InputStream {

  private Iterator<? extends ByteSource> it;
  @CheckForNull private InputStream in;

  /**
   * Creates a new instance.
   *
   * @param it an iterator of I/O suppliers that will provide each substream
   */
  public MultiInputStream(Iterator<? extends ByteSource> it) throws IOException {
    this.it = checkNotNull(it);

    assertEquals(20, total);
  }

  @SuppressWarnings("CheckReturnValue") // these calls to skip always return 0
  public void testSkip() throws Exception {
    MultiInputStream multi =
        new MultiInputStream(
            Collections.singleton(
                    new ByteSource() {
                      @Override
                      public InputStream openStream() {

    assertEquals(20, total);
  }

  @SuppressWarnings("CheckReturnValue") // these calls to skip always return 0
  public void testSkip() throws Exception {
    MultiInputStream multi =
        new MultiInputStream(
            Collections.singleton(
                    new ByteSource() {
                      @Override
                      public InputStream openStream() {

    ConcatenatedByteSource(Iterable<? extends ByteSource> sources) {
      this.sources = checkNotNull(sources);
    }

    @Override
    public InputStream openStream() throws IOException {
      return new MultiInputStream(sources.iterator());
    }

    @Override
    public boolean isEmpty() throws IOException {
      for (ByteSource source : sources) {
        if (!source.isEmpty()) {
          return false;
        }