Convert Map<String,Object> to Map<String,String>

Question

How can I convert Map<String,Object> to Map<String,String> ?

This does not work:

Map<String,Object> map = new HashMap<String,Object>(); //Object is containing String Map<String,String> newMap =new HashMap<String,String>(map); 

Answer 1

Now that we have Java 8/streams, we can add one more possible answer to the list:

Assuming that each of the values actually are String objects, the cast to String should be safe. Otherwise some other mechanism for mapping the Objects to Strings may be used.

Map<String,Object> map = new HashMap<>(); Map<String,String> newMap = map.entrySet().stream()      .collect(Collectors.toMap(Map.Entry::getKey, e -> (String)e.getValue())); 

Answer 2

If your Objects are containing of Strings only, then you can do it like this:

Map<String,Object> map = new HashMap<String,Object>(); //Object is containing String Map<String,String> newMap =new HashMap<String,String>(); for (Map.Entry<String, Object> entry : map.entrySet()) {        if(entry.getValue() instanceof String){             newMap.put(entry.getKey(), (String) entry.getValue());           }  } 

If every Objects are not String then you can replace (String) entry.getValue() into entry.getValue().toString().