Strange compile error in java -


this question has answer here:

i'm trying pass variable of type:

hashmap<foo, hashset<bar>>

to method, expects:

map<foo, set<bar>>

i think should work, i'm getting following compile error:

java: method setmenu in class com.xx.client.layout.layout cannot applied given types;    required: java.util.map<com.xx.shared.model.usertype,java.util.set<com.xx.shared.dto.model.menuitemdto>>    found: java.util.hashmap<com.xx.shared.model.usertype,java.util.hashset<com.xx.shared.dto.model.menuitemdto>>    reason: actual argument java.util.hashmap<com.xx.shared.model.usertype,java.util.hashset<com.xx.shared.dto.model.menuitemdto>>   cannot converted   java.util.map<com.xx.shared.model.usertype,java.util.set<com.xx.shared.dto.model.menuitemdto>>   method invocation conversion

to attempt convince you, given 

hashmap<foo, hashset<bar>> mymap;

you expect do

hashset<bar> ahashset = mymap.get(afoo);

but if had

public void somemethod(map<foo, set<bar>> amapparameter) {...}

and expected

somemethod(mymap);

to work, somemethod do

public void somemethod(map<foo, set<bar>> amapparameter) {     amapparameter.put(afoo, new treeset<>()); }

your original

hashset<bar> ahashset = mymap.get(afoo);

would fail classcastexception.

compile time type safety has guarantee doesn't happen. therefore compiler doesn't allow method call.

related:


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