CODEWITHSUNDEEP
javajava-8
user6601906
user6601906

Reputation:

unable to fetch set from map using java8

what I'm trying to do

Set<A> set=new HashSet();
Map<String,List<String>> map=new HashMap();
    if(map.keySet().contains("key"){
    for(String str: map.get("key")
    {
        for(A a : listOfA)
        {
            if(a.getString().equalsIgnoreCase(str);
            set.add(a);
        }
    }

    }

What I tried

if(map.keySet().contains("key")
{
    listOfA
    .stream()
     .filter(t->t.getString().equalsIgnoreCase(map.get("key")
                                               .stream
                                            .flatMap(c->c.toString()))
     .distinct()
     .collect(Collectors.toSet()):

}

//error The method equalsIgnoreCase(String) in the type String is not applicable for the arguments (Stream)

if(map.keySet().contains("key")
{
    map.get("key").stream().filter(t->t.equals(listOfA.stream().map(a->a.getString()))).collect(Collectors.toSet());
}

and this method returns Set<String>,obviously as output but I want Set<A> as output

so how to solve this, using functional programming

Upvotes: 3

Views: 97

Answers (2)

Holger
Holger

Reputation: 298469

The following solution might scale better if your listOfA is rather large:

List<String> value = map.getOrDefault("key", Collections.emptyList());
Collection<String> c;
if(value.isEmpty()) c=value;
else { c=new TreeSet<>(String.CASE_INSENSITIVE_ORDER); c.addAll(value); }
Set<A> set = listOfA.stream()
                    .filter(a->c.contains(a.getString()))
                    .collect(Collectors.toSet());

Upvotes: 2

Eran
Eran

Reputation: 393986

You can check if any String of map.get("key") is equalsIgnoreCase to getString() of a given A instance by streaming map.get("key") and using anyMatch :

List<String> value = map.get("key");
Set<A> set = null;
if (value != null) {
   set = listOfA.stream()
                .filter(a->value.stream()
                                .anyMatch(s->a.getString().equalsIgnoreCase(s)))
                .collect(Collectors.toSet());
}

Upvotes: 4

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