Java Map<K,V> : Why get(object) not get(K)? [duplicate]

Question

Possible Duplicate:
Java Generics: Why Does Map.get() Ignore Type?

Could someone please explain why with Map defines

V put(K key,V value);
V get(Object key);

Why is get not defined as:

V get(K key)

Similarly, why are these methods typed to Object, and not K and V respectively?

boolean containsKey(Object key); // Why not K?
boolean containsValue(Object value); // Why not V?

Is this a backwards compatibility thing (pre 1.5)?

Answer 1

Good explanations can be found in the answers of

What are the reasons why Map.get(Object key) is not (fully) generic

and

Java Generics: Why Does Map.get() Ignore Type?