Question

Can anyone help me to figure out difference between
SortedMap, CheckedSortedMap, synchronizedSortedMap.
I am really have trouble in making decision which one to use when?

Thanks in advance.

Answer 1

SortedMap is an interface that is a Map(key-value pairs) with an added contract of being ordered in some defined manner on its keys. Owing to that ordering of keys SortedMap has extra methods like SortedMap<K,V> subMap(K fromKey, K toKey), SortedMap<K,V> headMap(K toKey) ... which ‘normal’ Maps dont have. If you iterate a keyset of a sortedMap you will find a definite order.

A Treemap is an implementation of that interface. If you are creating a new SortedMap object by yourself, its almost always go for TreeSet.

For checkedSortedMap or any other Collections.checkedXXX() methods, Here is a fine discussion on what they all are for: What is the Collections.checkedList() call for in java?

Classes in Collections framework are not synchronized by default. For Maps it means that if you have a map that is shared between two or more threads and one is doing a put(A, value) and another thread is also calling put(A, othervalue) at the same time on the map, strange things can occur. Collections.synchronizedSortedMap(sortedMap) method gives a synchronized map that wraps the given map and with proper locking mechanisms in place.