hashmap - java insert in Map<String, Set<String>> -

in c++ can do:

map<string, set<string>> v;  v["aha"].insert("ba");

in java have:

 hashmap<string, set<string>> v = new hashmap<string, set<string>>();

how can insert "ba" v["aha"] c++?

yes try this:

set<string> vs = v.get("b"); if (vs == null) vs = new hashset<string>(); vs.add("v"); v.put("b", vs);

but large

if want add set, , allow possibility key/value pair might not yet exist in map, can use computeifabsent

v.computeifabsent("aha", k -> new hashset<string>()).add("ba")

this key in map, , if missing, add new empty set value, can add stuff straight it.

if you're using version of java before java 8, it's little more code:

set<string> s = v.get("aha"); if (s==null) {     s = new hashset<string>();     v.put("aha", s); } s.add("ba");

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