Here I am using Javaparallel stream to iterate through a List and calling a REST call with each list element as input. I need to add all the results of the REST call to a collection for which I am using an ArrayList
. The code given below is working fine except that the non-thread-safety of ArrayList would cause incorrect results, and adding needed synchronization would cause contention, undermining the benefit of parallelism.
Can someone please suggest me a proper way of using parallel stream for my case.
public void myMethod() {
List<List<String>> partitions = getInputData();
final List<String> allResult = new ArrayList<String>();
partitions.parallelStream().forEach(serverList -> callRestAPI(serverList, allResult);
}
private void callRestAPI(List<String> serverList, List<String> allResult) {
List<String> result = //Do a REST call.
allResult.addAll(result);
}
You can do the operation with map
instead of forEach
- that will guarantee thread safety (and is cleaner from a functional programming perspective):
List<String> allResult = partitions.parallelStream()
.map(this::callRestAPI)
.flatMap(List::stream) //flattens the lists
.collect(toList());
And your callRestAPI
method:
private List<String> callRestAPI(List<String> serverList) {
List<String> result = //Do a REST call.
return result;
}
I wouldn't shy away from synchronising access to your ArrayList
. Given that you're accessing a remote service via Rest, I suspect the cost of synchronisation would be negligible . I would measure the effect before you spend time optimising.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.