get result from multithread for the same method - multithreading

Question

I would like to parallelize my program to be fast, so my program is like that:
Sim1 sim1 = new Sim1();
for(Entry<Integer, HashSet<String>> entry : map_topics_words.entrySet()) {
Integer k = entry.getKey();
Double sim = sim1.prob(word_m, entry.getValue());
sim_avg.put(k, sim);
score += sim;
}
and prob in the method in class Sim1 like that
public double prob(String w_i, HashSet<String> set_i){
Similarity sim = new Similarity();
double score = 1;
Iterator<String> it = set_i.iterator();
while (it.hasNext()) {
score += sim.computeSim(w_i, it.next());
}
score = score/set_i.size();
return score;
}
and computeSim in the method in classe Similarity like that :
public double computeSim(String w_1, String w_2){
return cmp(w_1,w_2);
}
So I would like to use thread for the first method and thread for the second method, I tried different ways but I failed
Any help, please
Thank you

Answer 1

You can change the first method code as below. We can try this by using Executor framework by submitting the work of prob() method as Callable task so that It can be executed in different thread, and then by using Future we can get the result for that particular call, for this we need to maintain one more map of key and corresponding Future object, Please see below code to understand it better, hope it may help you.
Sim1 sim1 = new Sim1();
Map<Integer, Future<Double>> workerMap = new HashMap<>();
ExecutorService exe = Executors.newCachedThreadPool();
for(Map.Entry<Integer, HashSet<String>> entry : map_topics_words.entrySet()) {
Integer k = entry.getKey();
workerMap.put(k, exe.submit(()->{ //Java 8 lamda
return sim1.prob(word_m, entry.getValue());
}));
}
//This loop is to get the result of prob() method for all the keys and process them further
for(Map.Entry<Integer, HashSet<String>> entry : map_topics_words.entrySet()) {
Integer k = entry.getKey();
try {
Double sim = workerMap.get(k).get();
sim_avg.put(k, sim);
score += sim;
} catch (Exception e) {
e.printStackTrace();
}
}
I will suggest you to google the working of Callable and Future in java, You can see this link also.