HashMap of HashMaps traversal

In Java, I'm trying to retrieve a HashMap<String, Object> that has the Object which is: HashMap<String, Object&g开发者_StackOverflowt;.

I implemented a recursive function that returns either the HashMap<String, Object> found with the given key, or null if the key wasn't found.

Here is the function:

public static HashMap<String, Object> getHashMap(HashMap<String, 
                                      Object> map, String key)
{
    for (Map.Entry<String, Object> entry : map.entrySet()) {
     if (entry.getValue().getClass().getName() == "java.util.HashMap") {
         if (entry.getKey() == key) 
          return (HashMap<String, Object>) entry.getValue();
         return getHashMap((HashMap<String, Object>) entry.getValue(), key);
     }
    }
    return null;
}

It only works for the first item. How do I traverse a Hashmap of HashMaps? What is a better approach?

Instead of returning the value immediately here:

return getHashMap((HashMap<String, Object>) entry.getValue(), key);

you want to first check if it is not null, and return it only then. Otherwise you should just continue searching:

HashMap<String, Object> result = getHashMap((HashMap<String, Object>) entry.getValue(), key);
if (result != null)
  return result;

For one, don't use == for Strings. Instead use the equals method.

For another, I prefer to do instanceof such as if (myObject instanceof java.util.Map) { ... } this way your map doesn't have to be a HashMap if later you decide to change it.

Another approach. Try use HashMap<String, HashMap<String, Object>> main for your 'outer' HashMap, then you'll search for key:

Object value = main.get(key);
if (value == null) {
    for (HashMap<String, Object> inner : main.values()) {
        value = inner.get(key);
        if (value != null) {
            break;
        }
    }
}