Java HashMap<String, String> has LinkedHashMap in value

Question

So I have a strange issue with a HashMap and not sure how to access the value. I have a HashMap returned to me from an API that is suppose to be HashMap<String, String>. One of the values is actually a LinkedHashMap. I've tried casting it, but since it is a HashMap that is <String, String> it's giving me an error that it's not possible. Is there anyway to get a LinkedHashMap value out of a HashMap that is <String, String>?

I have tried this with no luck: ((HashMap)userInfo.get("key")).get("key");

     Could not complete request <java.lang.ClassCastException: 
java.util.LinkedHashMap cannot be cast to java.lang.String>java.lang.ClassCastException:

java.util.LinkedHashMap cannot be cast to java.lang.String

This is really ugly looking, but I was actually able to get it out of the HashMap with this:

(HashMap) ((HashMap)((HashMap)userInfo).get("picture")).get("data");

Thanks to Jeroen for sending me down the right path.

You need to provide more code and the error you get, otherwise your question isn't very clear. — vanza
– vanza, Commented Oct 23, 2013 at 15:57
LinkedHashMap is a subclass of HashMap, so why not just use the LinkedHashMap as a HashMap? — Kakalokia
– Kakalokia, Commented Oct 23, 2013 at 15:58
If your library is returning a raw HashMap without generics, it's probably very old and hard to work with. Look for something better. — Matthijs Bierman
– Matthijs Bierman, Commented Oct 23, 2013 at 15:59
Why do you want to cast it? You can call get on a LinkedHashMap just the same... — Henry Keiter
– Henry Keiter, Commented Oct 23, 2013 at 16:01
You can't put a LinkedHashMap as a value in a HashMap<String,String>. It shouldn't be possible, unless the library was using a raw type without generics. — Matthijs Bierman
– Matthijs Bierman, Commented Oct 23, 2013 at 16:25

Jeroen Vannevel · Accepted Answer · 2013-10-23 15:57:22Z

1

Brackets placement.

Try

(((HashMap)userInfo).get("key")).get("key");

You have to cast before you use .get() (assuming your attempt is actually valid and it is just a matter of brackets).

answered Oct 23, 2013 at 15:57

Jeroen Vannevel

44.6k25 gold badges113 silver badges174 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Michael Over a year ago

Does not work, complains about casting since the HashMap this is working on is <String, String>

Michael Over a year ago

Ok I took it one step further and this actually works... even though it is pretty ugly: (HashMap) ((HashMap)((HashMap)userInfo).get("picture")).get("data");

Michael Over a year ago

I'll give you the answer since you sent me down the right path :)

Juha Syrjälä · Accepted Answer · 2013-10-23 16:42:16Z

1

Convert typed map first to untyped map and then check type of each value. Map interface is implemented by HashMap and LinkedHashMap classes so you'll most likely want to use it instead of more specific types.

HashMap<String, String> typedMap = ...
Map untypedMap = (Map) typedMap;
Object mapValue = untypedMap.get("key");

if(mapValue instanceof Map) {
  // handle as Map
}

if(mapValue instanceof String) {
  // handle as String
}

edited Oct 23, 2013 at 16:42

answered Oct 23, 2013 at 16:35

Juha Syrjälä

34.4k33 gold badges137 silver badges191 bronze badges

Comments

OldCurmudgeon · Accepted Answer · 2013-10-23 15:58:30Z

0

If it is a LinkedHashMap and you cast it to a HashMap you will have probelms.

You could instead treat it as a Map:

Map m = userInfo.get("key");

answered Oct 23, 2013 at 15:58

OldCurmudgeon

66k18 gold badges126 silver badges220 bronze badges

2 Comments

Matthijs Bierman Over a year ago

Really? LinkedHashMap extends HashMap!

Michael Over a year ago

Not sure how it would be confusing, in the title and various places it shows it is using generics <String, String> so return value is going to be a string.

Collectives™ on Stack Overflow

Java HashMap<String, String> has LinkedHashMap in value

3 Answers 3

3 Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related