The note about Java 8 Parallel Streams vs ExecutorService

 The Java 8 parallel streams look neat, compact and easy, however, it has limitations you cannot specify the thread number or thread pool.

I did a comparison using the two implementations, I have a list of stock code, and need access the URL to get the name for the code list (3470 code).

For serial retrieval, it needs 900+ seconds.

For parallel streams retrieval, it spends 138 seconds.

For ExecutorService, it spends 45 seconds for 20 threads, 18 seconds for 50 threads, and 5.75 seconds for 200 threads.

//from 900+ seconds to 138 seconds for parallelStream
List<Code> codeList = codeStringList.parallelStream().map( (code)->{
   String name = null;
   try {
      name = SinaDataProvider.getName(code);
   } catch (IOException e) {
      logger.error("Fatal error to get name for "+code+","+e.getMessage());
      e.printStackTrace();
   }
   logger.debug(code+","+name);
   Code codeObj = new Code();
   codeObj.setCode(code);
   //remove blank space from name
   codeObj.setName(name.replaceAll("\\s",""));
   codeObj.setStart_time(yyyyMMdd);
   codeObj.setEnd_time("");
   return codeObj;
}).collect(Collectors.toList());

//45 seconds for 20 threads for ExecutorService 
//18 seconds for 50 threads
//5.75 seconds for 200 threads
ExecutorService executor = Executors.newFixedThreadPool(200);
Collection<Future<Code>> futures = new LinkedList<Future<Code>>();
for(String code:codeStringList){
   futures.add(
         executor.submit(()->{
            String name = null;
            try {
               name = SinaDataProvider.getName(code);
            } catch (IOException e) {
               logger.error("Fatal error to get name for "+code+","+e.getMessage());
               e.printStackTrace();
            }
            logger.debug(code+","+name);
            Code codeObj = new Code();
            codeObj.setCode(code);
            //remove blank space from name
            codeObj.setName(name.replaceAll("\\s",""));
            codeObj.setStart_time(yyyyMMdd);
            codeObj.setEnd_time("");
            return codeObj;
         }));
};
List<Code> codeList = new ArrayList<>();
for (Future<Code> future : futures) {
   try {
      Code codeObj = future.get();
      codeList.add(codeObj);
   } catch (Exception e) {
      throw new RuntimeException(e);
   }
}
executor.shutdown();