- Ordered map:
- Entries stored in the map is ordered by the key value
- Example:
- A dictionary....
- Additional operations:
- firstEntry():
- Return the entry with the
smallest key value
Return null is the map is empty
- Return the entry with the
smallest key value
- lastEntry():
- Return the entry with the
largest key value
Return null is the map is empty
- Return the entry with the
largest key value
- ceilingEntry(Key k):
- Return the entry with the
smallest key value that
is ≥ k
Graphically: (round up from key k)
k Stored keys: | V ------------+---------+--------+------+----+---- ^ | ceilingEntry(k)
- Return the entry with the
smallest key value that
is ≥ k
- floorEntry(Key k):
- Return the entry with the
largest key value that
is ≤ k
Graphically: (round down from key k)
k Stored keys: | V ------------+---------+--------+------+----+---- ^ | floorEntry(k)
- Return the entry with the
largest key value that
is ≤ k
- upperEntry(Key k):
- Return the entry with the
smallest key value that
is > k
Graphically: (go up from key k)
k Stored keys: | V ------------+---------+--------+------+----+---- ^ | upperEntry(k)Note: upperEntry(k) == ceilingEntry(k) if k is not a key in the map
- Return the entry with the
smallest key value that
is > k
- lowerEntry(Key k):
- Return the entry with the
largest key value that
is < k
Graphically: (go down from key k)
k Stored keys: | V ------------+---------+--------+------+----+---- ^ | lowerEntry(k)Note: lowerEntry(k) == floorEntry(k) if k is not a key in the map
- Return the entry with the
largest key value that
is < k
- firstEntry():
- Java has implmented the
Ordered Map data structure.
The functionality of the Ordered Map is specified by the following interface:
java.util Interface NavigableMap<K,V> Type Parameters: K - the type of keys maintained by this map V - the type of mapped values All Known Implementing Classes: ConcurrentSkipListMap, TreeMapSee: click here
- Example program:
public class OrderedMap1 { public static void main( String[] args ) { NavigableMap<Integer, String> S = new TreeMap&;Integer, String>(); S.put( 12, "a" ); S.put( 30, "b" ); S.put( 40, "d" ); S.put( 19, "c" ); S.put( 49, "e" ); S.put( 33, "x" ); S.put( 35, "y" ); S.put( 37, "z" ); System.out.println( S ); System.out.println(); // Map manipulation System.out.println( "S.firstEntry() = " + S.firstEntry() ); System.out.println( "S.lastEntry() = " + S.lastEntry() ); System.out.println(); System.out.println( "S.ceilingEntry(30) = " + S.ceilingEntry(30) ); System.out.println( "S.floorEntry(30) = " + S.floorEntry(30) ); System.out.println( "S.higherEntry(30) = " + S.higherEntry(30) ); System.out.println( "S.lowerEntry(30) = " + S.lowerEntry(30) ); System.out.println(); System.out.println( "S.ceilingEntry(31) = " + S.ceilingEntry(31) ); System.out.println( "S.floorEntry(31) = " + S.floorEntry(31) ); } }Output:
{12=a, 19=c, 30=b, 33=x, 35=y, 37=z, 40=d, 49=e} S.firstEntry() = 12=a S.lastEntry( ) = 49=e S.ceilingEntry(30) = 30=b (>= 30) S.floorEntry(30) = 30=b (<= 30) S.higherEntry(30) = 33=x (> 30) S.lowerEntry(30) = 19=c (< 30) S.ceilingEntry(31) = 33=x (>= 31) S.floorEntry(31) = 30=b (<= 31)
- Example Program:
(Demo above code)
- Prog file: click here
How to run the program:
- Right click on link(s) and
save in a scratch directory
- To compile: javac OrderedMap1.java
- To run: java OrderedMap1