List<String> list =
        source.readLines(
            new LineProcessor<List<String>>() {
              final List<String> list = new ArrayList<>();

              @Override
              public boolean processLine(String line) throws IOException {
                list.add(line);
                return true;
              }

              @Override
              public List<String> getResult() {

    List<String> list =
        lines.readLines(
            new LineProcessor<List<String>>() {
              final List<String> list = new ArrayList<>();

              @Override
              public boolean processLine(String line) throws IOException {
                list.add(line);
                return true;
              }

              @Override
              public List<String> getResult() {

    LineProcessor<List<String>> collect =
        new LineProcessor<List<String>>() {
          final List<String> collector = new ArrayList<>();

          @Override
          public boolean processLine(String line) {
            collector.add(line);
            return true;
          }

          @Override
          public List<String> getResult() {
            return collector;
          }

    LineProcessor<List<String>> collectAndLowercaseAndTrim =
        new LineProcessor<List<String>>() {
          final List<String> collector = new ArrayList<>();

          @Override
          public boolean processLine(String line) {
            collector.add(whitespace().trimFrom(line));
            return true;
          }

          @Override
          public List<String> getResult() {
            return collector;

    LineProcessor<List<String>> collectAndLowercaseAndTrim =
        new LineProcessor<List<String>>() {
          final List<String> collector = new ArrayList<>();

          @Override
          public boolean processLine(String line) {
            collector.add(whitespace().trimFrom(line));
            return true;
          }

          @Override
          public List<String> getResult() {
            return collector;

    public <T extends @Nullable Object> T readLines(LineProcessor<T> processor) throws IOException {
      Iterator<String> lines = linesIterator();
      while (lines.hasNext()) {
        if (!processor.processLine(lines.next())) {
          break;
        }
      }
      return processor.getResult();
    }

    @Override
    public String toString() {