multithreading - Parallel stream creates only one thread and gives result as fast as normal stream -

below code try process lines read file in parallel stream , in normal stream. surprisingly, parallel stream gives no improvements on normal stream . missing here ?

files.walk(paths.get(tweetfilepath + localdate.now())).foreach(             filepath -> {                 if (files.isregularfile(filepath) && !filepath.tostring().endswith(".ds_store")) {                     long starttime = system.currenttimemillis();                     try {                          files.lines(filepath).parallel().foreach(line -> {                                 try {                                     system.out.println(line);                                  } catch (exception e) {                                     system.out.println("not able crunch"+ e);                                 }                          });                     } catch (exception e) {                         system.out.println("bad line in file ");                     }finally {                         system.out.println("total time required:" + (system.currenttimemillis() - starttime));                      }                    }             }); 

looks currently, files.lines reads file linearly, parallel call cannot split source stream sub-streams parallel processing.

see here details. relevant section quoted below:

what if source based on io?

currently, jdk io-based stream sources (for example bufferedreader.lines()) geared sequential use, processing elements one-by-one arrive. opportunities exist supporting highly efficient bulk processing of buffered io, these require custom development of stream sources, spliterators, and/or collectors. common forms may supported in future jdk releases.