/**
 * A {@link Reader} that concatenates multiple readers.
 *
 * @author Bin Zhu
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
final class MultiReader extends Reader {
  private final Iterator<? extends CharSource> it;
  private @Nullable Reader current;

  MultiReader(Iterator<? extends CharSource> readers) throws IOException {
    this.it = readers;
    advance();
  }

    ConcatenatedCharSource(Iterable<? extends CharSource> sources) {
      this.sources = checkNotNull(sources);
    }

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

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

    ConcatenatedCharSource(Iterable<? extends CharSource> sources) {
      this.sources = checkNotNull(sources);
    }

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

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