code: public static <T> Stream<T> parallelConcatt(final Collection<? extends Iterator<? extends T>> c, final int readThreadNum) {
          return parallelConcatt(c, readThreadNum, calculateQueueSize(c.size()));
      }
docs: Put the stream in try-catch to stop the back-end reading thread if error happens
  <br />
  <code>
  try (Stream<Integer> stream = Stream.parallelConcat(a,b, ...)) {
  stream.forEach(N::println);
  }
  </code>
  
  @param c
  @param readThreadNum
  @return