Java Collection Framework - Sorted Map Interface

The Collection Framework provides a special Map interface for maintaining elements in a sorted order called SortedMap.

The interface provides access methods to the ends of the map as well to subsets of the set. Working with a SortedMap is just like a SortedSet, except the sort is done on the map keys. The implementation class provided by the Collection Framework is a TreeMap.

Comparator	comparator() Returns the comparator associated with this sorted map, or null if it uses its keys' natural ordering.
Object	firstKey() Returns the first (lowest) key currently in this sorted map.
SortedMap	headMap(Object toKey) Returns a view of the portion of this sorted map whose keys are strictly less than toKey.
Object	lastKey() Returns the last (highest) key currently in this sorted map.
SortedMap	subMap(Object fromKey, Object toKey) Returns a view of the portion of this sorted map whose keys range from fromKey, inclusive, to toKey, exclusive.
SortedMap	tailMap(Object fromKey) Returns a view of the portion of this sorted map whose keys are greater than or equal to fromKey.