Map vs Map<K,V>

Question

I'd like to find out why UnmodifiableMap.decorate(Map map) from Apache Commons operates on Map and returns Map instead of Map<K,V> . What's the difference between these two approaches?

Answer 1

I believe the Apache Commons collections predate generics, and haven't been updated for them.

You may wish to look at this unofficial version which is a port of Apache Commons Collections to generics, or at Guava for an alternative library with support for other collections. (There are others, of course.)

Answer 2

I think it is because of some sort of backward compatibility. The Map<K,V> can be used just in Java 5 and above.

Answer 3

Jon is probably right.

You may be able to cast to Map when it's retruned.

Map<K,V> myMap = (Map<K,V>)UnmodifiableMap.decorate(Map map);