}
    },
    NEW {
      @Override
      long copy(Readable from, Appendable to) throws IOException {
        return CharStreams.copy(from, to);
      }
    };

    abstract long copy(Readable from, Appendable to) throws IOException;
  }

  enum TargetSupplier {
    STRING_WRITER {
      @Override
      Appendable get(int sz) {
        return new StringWriter(sz);
      }
    },
    STRING_BUILDER {

  private static class SpyAppendable implements Appendable, Flushable, Closeable {
    boolean flushed;
    boolean closed;
    final StringBuilder result = new StringBuilder();

    @Override
    public Appendable append(CharSequence csq) {
      result.append(csq);
      return this;
    }

    @Override
    public Appendable append(char c) {
      result.append(c);
      return this;
    }

/**
 * Writer that places all output on an {@link Appendable} target. If the target is {@link Flushable}
 * or {@link Closeable}, flush()es and close()s will also be delegated to the target.
 *
 * @author Alan Green
 * @author Sebastian Kanthak
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
final class AppendableWriter extends Writer {
  private final Appendable target;
  private boolean closed;

  /**