*
   * @param sources the sources to concatenate
   * @return a {@code CharSource} containing the concatenated data
   * @since 15.0
   */
  public static CharSource concat(Iterable<? extends CharSource> sources) {
    return new ConcatenatedCharSource(sources);
  }

  /**
   * Concatenates multiple {@link CharSource} instances into a single source. Streams returned from

    String testString = "abcdefgh";
    CharSource source = newCharSource(testString);
    Reader joinedReader = CharSource.concat(source, source).openStream();

    String expectedString = testString + testString;
    assertThat(CharStreams.toString(joinedReader)).isEqualTo(expectedString);
  }

  private static CharSource newCharSource(String text) {
    return new CharSource() {
      @Override
      public Reader openStream() {

    CharSource c1 = CharSource.wrap("abc");
    CharSource c2 = CharSource.wrap("");
    CharSource c3 = CharSource.wrap("de");

    String expected = "abcde";

    assertThat(CharSource.concat(ImmutableList.of(c1, c2, c3)).read()).isEqualTo(expected);
    assertThat(CharSource.concat(c1, c2, c3).read()).isEqualTo(expected);

 * Generates tests of all methods on a {@code CharSource} given various inputs the source is
 * expected to contain.
 *
 * @author Colin Decker
 */
@AndroidIncompatible // TODO(b/230620681): Make this available (even though we won't run it).
@NullUnmarked
public class CharSourceTester extends SourceSinkTester<CharSource, String, CharSourceFactory> {

 * Utility methods and classes for I/O; for example input streams, output streams, readers, writers,
 * and files.
 *
 * <p>At the core of this package are the Source/Sink types: {@link ByteSource ByteSource}, {@link
 * CharSource CharSource}, {@link ByteSink ByteSink} and {@link CharSink CharSink}. They are
 * factories for I/O streams that provide many convenience methods that handle both opening and
 * closing streams for you.
 *

 *
 * @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();
  }

  /** Closes the current reader and opens the next one, if any. */

        factory.tearDown();
      }
    };
  }

  private static class StringSourceFactory implements CharSourceFactory {

    @Override
    public CharSource createSource(String data) throws IOException {
      return CharSource.wrap(data);
    }

    @Override
    public String getExpected(String data) {
      return data;
    }

    @Override

  /** Factory for {@link ByteSink} instances. */
  interface ByteSinkFactory extends SinkFactory<ByteSink, byte[]> {}

  /** Factory for {@link CharSource} instances. */
  interface CharSourceFactory extends SourceFactory<CharSource, String> {}

  /** Factory for {@link CharSink} instances. */
  interface CharSinkFactory extends SinkFactory<CharSink, String> {}

  /** Factory for {@link ByteSink} instances. */
  interface ByteSinkFactory extends SinkFactory<ByteSink, byte[]> {}

  /** Factory for {@link CharSource} instances. */
  interface CharSourceFactory extends SourceFactory<CharSource, String> {}

  /** Factory for {@link CharSink} instances. */
  interface CharSinkFactory extends SinkFactory<CharSink, String> {}

import java.io.Reader;
import org.jspecify.annotations.NullUnmarked;

/**
 * A char source for testing that has configurable options.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class TestCharSource extends CharSource implements TestStreamSupplier {

  private final TestByteSource byteSource;

  public TestCharSource(String content, TestOption... options) {
    this.byteSource = new TestByteSource(content.getBytes(UTF_8), options);