*
   * @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);
    advance();
  }

  @Override
  public void close() throws IOException {
    if (in != null) {
      try {
        in.close();
      } finally {
        in = null;
      }
    }
  }

    this.it = readers;
    advance();
  }

  /** Closes the current reader and opens the next one, if any. */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {
      current = it.next().openStream();
    }
  }

  @Override
  public int read(char[] cbuf, int off, int len) throws IOException {
    checkNotNull(cbuf);

   *
   * <p>Prefer this method instead of manually casting an exception's cause. For example, {@code
   * (IOException) e.getCause()} throws a {@link ClassCastException} that discards the original
   * exception {@code e} if the cause is not an {@link IOException}, but {@code
   * Throwables.getCauseAs(e, IOException.class)} keeps {@code e} as the {@link
   * ClassCastException}'s cause.
   *

   *
   * <p>Prefer this method instead of manually casting an exception's cause. For example, {@code
   * (IOException) e.getCause()} throws a {@link ClassCastException} that discards the original
   * exception {@code e} if the cause is not an {@link IOException}, but {@code
   * Throwables.getCauseAs(e, IOException.class)} keeps {@code e} as the {@link
   * ClassCastException}'s cause.
   *

    String separator = "\r\n";
    sink.writeLines(lines, separator);

    assertContainsExpectedLines(separator);
  }

  private void assertContainsExpectedString() throws IOException {
    assertEquals(expected, factory.getSinkContents());
  }

  private void assertContainsExpectedLines(String separator) throws IOException {

   * Reads all bytes from a URL into a byte array.
   *
   * @param url the URL to read from
   * @return a byte array containing all the bytes from the URL
   * @throws IOException if an I/O error occurs
   */
  public static byte[] toByteArray(URL url) throws IOException {
    return asByteSource(url).read();
  }

  /**
   * Reads all characters from a URL into a {@link String}, using the given character set.
   *

    assertTrue(spy.closed);
  }

  public void testCloseIsFinal() throws IOException {
    StringBuilder builder = new StringBuilder();
    Writer writer = new AppendableWriter(builder);

    writer.write("Hi");
    writer.close();

    assertThrows(IOException.class, () -> writer.write(" Greg"));

    assertThrows(IOException.class, () -> writer.flush());

    // close()ing already closed writer is allowed

      @Override
      public int read(CharBuffer cbuf) throws IOException {
        return reader.read(cbuf);
      }
    };
  }

  private static Reader getChunkedReader(String input, final int chunk) {
    return new FilterReader(new StringReader(input)) {
      @Override
      public int read(char[] cbuf, int off, int len) throws IOException {
        return super.read(cbuf, off, Math.min(chunk, len));
      }

  @Override
  public void mark(int readlimit) {}

  /**
   * reset() is not supported for HashingInputStream.
   *
   * @throws IOException this operation is not supported
   */
  @Override
  public void reset() throws IOException {
    throw new IOException("reset not supported");
  }

  /**
   * Returns the {@link HashCode} based on the data read from this stream. The result is unspecified

  }

  public void testWrite() throws IOException {
    sink.write(data);

    assertContainsExpectedBytes();
  }

  public void testWriteFrom_inputStream() throws IOException {
    sink.writeFrom(new ByteArrayInputStream(data));

    assertContainsExpectedBytes();
  }

  private void assertContainsExpectedBytes() throws IOException {
    assertArrayEquals(expected, factory.getSinkContents());