Generics bug or just me being stupid?

Question

Heya, does anyone know why this doesnt work?
   @SuppressWarnings("unchecked")
   private Map.Entry<String, Map<String, Serializable>> safeCast(Map.Entry<String, Serializable> entry)
      if ((entry.getValue() instanceof Map<?, ?>) == false)
         throw new ClassCastException();
      return (Map.Entry<String, Map<String, Serializable>>)entry;
   }Gives me:
MoniterMessage.java:45: inconvertible types
found   : java.util.Map.Entry<java.lang.String,java.io.Serializable>
required: java.util.Map.Entry<java.lang.String,java.util.Map<java.lang.String,ja
va.io.Serializable>>
      return (Map.Entry<String, Map<String, Serializable>>)entry;It is a tree-like structure, a map can contain either Serializable objects or instances of Map. If the entry is an instance of map we want to add it to the folders list etc

Answer 1

@SuppressWarnings("unchecked")
private <T extends Map<String, Serializable>,
Serializable> Map.Entry<String, T>Here, you are creating a type parameter called Serializable. I guess you don't want to do that.
Generics should save you from casting, instanceof, etc. If you want the thing in your map to be both Serializable and Map, say so:
<V extends Map & Serializable, T extends Map<String, V>>(or something like that - I don't have the time to test it right now)