CODEWITHSUNDEEP
javadictionarycasting
KoichiSenada
KoichiSenada

Reputation: 183

How to cast a Map<?,?> into a typed Map in Java?

Assume we have multiple different untyped Map<?,?> maps of unknown type keys and unknown type values and it is known that there are Map<String,Object> and Map<Integer,Object> maps among them.

Whether is there a way to check and distinct and safely cast them into appropriate typed maps?

Upvotes: 1

Views: 1634

Answers (2)

banjara
banjara

Reputation: 3890

try

if(((Map.Entry)map.entrySet().iterator().next()).getKey().getClass().getName().equals("java.lang.Integer")){
            System.out.println("Map<Integer,Object>");
        }else{
            System.out.println("Map<String,Object>");
        }

Upvotes: 1

Tom Johnson
Tom Johnson

Reputation: 220

Due to type erasure, it's not possible to determine the type parameters of a generic class at runtime. However, if the maps are populated, and you know that each Map is either a Map(String, Object) or a Map(Integer, Object), you could simply inspect the first key from each Map and cast accordingly.

What's the use-case for this?

Upvotes: 1

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