Instantiates a new hashmap object,
 i.e. an unordered collection of key-value pairs with mapping
 $$f: keys -> values$$, where only unique key-value pairs
 can be stored.
hashmap(key.class = c("character", "numeric", "integer"))
| key.class | the primitive class type of the keys | 
|---|
returns a new hashmap object
# creates a hashmap<character, SEXP> h <- hashmap() # creates a hashmap<integer, SEXP> h <- hashmap("integer") # creates a hashmap<numeric, SEXP> h <- hashmap("numeric")