@GwtIncompatible
@ElementTypesAreNonnullByDefault
public interface LineProcessor<T extends @Nullable Object> {

  /**
   * This method will be called once for each line.
   *
   * @param line the line read from the input, without delimiter
   * @return true to continue processing, false to stop
   */
  @CanIgnoreReturnValue // some uses know that their processor never returns false
  boolean processLine(String line) throws IOException;