appendable.append(joiner.separator);
          Entry<?, ?> e = parts.next();
          appendable.append(joiner.toString(e.getKey()));
          appendable.append(keyValueSeparator);
          appendable.append(joiner.toString(e.getValue()));
        }
      }
      return appendable;
    }

    /**
     * Appends the string representation of each entry in {@code entries}, using the previously

        final String tag = element.getTagName();
        buf.append('<');
        buf.append(tag);
        appendAttrs(element.getAttributes(), buf);
        buf.append('>');
        appendChildren(element.getChildNodes(), buf);
        buf.append("</");
        buf.append(tag);
        buf.append('>');
    }

    /**
     * Appends the string representation of a {@link NodeList}.
     *

                tempBuf.append(Arrays.toString((double[]) value));
            } else {
                tempBuf.append('"').append(StringEscapeUtils.escapeJson(value.toString())).append('"');
            }
        } catch (final Exception e) {
            tempBuf.append("null");
        }
        buf.append(tempBuf.toString());
        return buf;
    }

    /**
     * Appends a timestamp to the buffer.
     *

      return "[]";
    }
    StringBuilder builder = new StringBuilder(length() * 5); // rough estimate is fine
    builder.append('[').append(array[start]);

    for (int i = start + 1; i < end; i++) {
      builder.append(", ").append(array[i]);
    }
    builder.append(']');
    return builder.toString();
  }

  /**

      return "[]";
    }
    StringBuilder builder = new StringBuilder(length() * 5); // rough estimate is fine
    builder.append('[').append(array[start]);

    for (int i = start + 1; i < end; i++) {
      builder.append(", ").append(array[i]);
    }
    builder.append(']');
    return builder.toString();
  }

  /**

    }
  }

  @Override
  public Writer append(char c) throws IOException {
    checkNotClosed();
    target.append(c);
    return this;
  }

  @Override
  public Writer append(@Nullable CharSequence charSeq) throws IOException {
    checkNotClosed();
    target.append(charSeq);
    return this;
  }

  @Override

     * The chain starts with the default filter chain and appends each registered filter.
     */
    protected void createFilterChain() {
        FilterChain chain = createDefaultFilterChain();
        for (final Filter element : filterList) {
            chain = appendFilterChain(element, chain);
        }
        filterChain = chain;
    }

    /**
     * Appends a filter to the existing filter chain.
     *

            if (values == null) {
                // nothing
            } else if (values.length == 1) {
                queryBuf.append(' ').append(key).append(":\"").append(values[0]).append('\"');
            } else if (values.length > 1) {
                boolean first = true;
                queryBuf.append(" (");
                for (final String value : values) {
                    if (first) {
                        first = false;

     * @param chain the existing filter chain to append to
     * @return a new filter chain that includes the appended filter
     */
    protected FilterChain appendFilterChain(final Filter filter, final FilterChain chain) {
        return (context, query, boost) -> filter.execute(context, query, boost, chain);
    }

    /**
     * Creates the default filter chain that executes query commands.

     * @return new referral, combining a chain of referrals
     */
    DfsReferralDataInternal combine(DfsReferralData next);

    /**
     * Append another referral to this referral chain
     *
     * @param dr the referral to append
     */
    void append(DfsReferralDataInternal dr);