Why does Java's Hashtable's get method take an Object as a parameter?

Question

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

From the JDK Documentation, the put method:

  public V put(K key, V value)

but, the get method:

  public V get(Object key)

Any ideas?

Note: In some code I inherited, there is a bug, where someone used a String as a parameter to the get method of a Hashtable with an Integer key.

Answer 1

This allows any Object which is equivalent to a given key to get the value.

For example, you may have two classes that override the equals method to return true in case of being compared to each-other. Since the objects are equivalent, they should both be able to get the value.

This is the same reason the equals method has an Object parameter.

Answer 2

The get method will take any Object as the key simply because any object is able to be stored in a HashMap (as all objects are a subclass of type Object).

It just checks the .equals method for that Object to return the match in the HashMap.

Answer 3

Semi-duplicate : http://stackoverflow.com/questions/1145121/why-does-this-code-with-generics-compile/1145126#1145126

The link is also a duplicate :P It talks about Map not HashTable but the reasoning is the same.