Collections and Generics - SCJP Sun Certified Programmer for Java Platform SE6 - page 448

The NavigableMap Interface
The TreeMap class implements the NavigableMap interface, which contains methods
similar to the NavigableSet interface for navigating and searching a map. Here are some
of the methods in NavigableMap :
Map.Entry<K,V> ceilingEntry(K key) returns a key-value mapping associated with
the least key greater than or equal to the given key.
K ceilingKey(K key) returns the least key greater than or equal to the given key.
Map.Entry<K,V> floorEntry(K key) returns a key-value mapping associated with
the greatest key less than or equal to the given key.
K floorKey(K key) returns the greatest key less than or equal to the given key.
NavigableSet<K> descendingKeySet() returns a reverse order NavigableSet view
of the keys contained in this map.
NavigableMap<K,V> descendingMap() returns a reverse order view of the mappings
contained in this map.
NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive, K toKey,
boolean toInclusive) returns a view of the portion of this map whose keys range
from fromKey to toKey .
The interface also defi nes headMap and tailMap methods for obtaining subsets at the
beginning and end of the map. Let's look at an example. The following TreeMap contains
26 character and integer pairs:
TreeMap<Character, Integer> ascii = new TreeMap<Character, Integer>();
int value = 97;
for(char c = 'a'; c <= 'z'; c++) {
ascii.put(c, value++);
}
Study the following code and see if you can determine its result:
12. Map.Entry<Character, Integer> ceiling = ascii.ceilingEntry('h');
13. System.out.println(“ceiling: “ + ceiling);
14. SortedMap<Character, Integer> tailMap = ascii.tailMap('t');
15. Set<Character> tailKeys = tailMap.keySet();
16. for(Character key : tailKeys) {
17. System.out.print(key + “ “);
18. }
19. System.out.println();
20. NavigableSet<Character> keys = ascii.descendingKeySet();