Finding greatest number less than given value is used in many a places and having that feature in a map based container is always a plus. Java.util.TreeMap also offers this functionality using floor() function. There are 2 variants, both are discussed below.
1. floorEntry() : It returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.
Parameters: key : This is the key to be matched. Return Value: It returns an entry with the greatest key less than or equal to key, or null if there is no such key. Exception: ClassCastException : This exception is thrown if the specified key cannot be compared with the keys currently in the map. NullPointerException : This exception is thrown if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.
// Java code to demonstrate the working // of floorEntry() import java.io.*;
import java.util.*;
public class floorEntry {
public static void main(String[] args)
{
// Declaring the tree map of Integer and String
TreeMap<Integer, String> tmp = new TreeMap<Integer, String>();
// assigning the values in the tree map
// using put()
tmp.put( 10 , "ten" );
tmp.put( 7 , "seven" );
tmp.put( 19 , "nineteen" );
tmp.put( 3 , "three" );
// use of floorEntry()
// displays the floor value of 6
// prints 3=three
System.out.println( "The greatest key-value less than 6 is : " + tmp.floorEntry( 6 ));
}
} |
Output:
The greatest key-value less than 6 is : 3=three
2. floorKey() : It returns the greatest key less than or equal to the given key, or null if there is no such key.
Parameters: key : This is the key to be matched. Return Value: It returns an entry with the greatest key less than or equal to key, or null if there is no such key. Exception: ClassCastException : This exception is thrown if the specified key cannot be compared with the keys currently in the map. NullPointerException : This exception is thrown if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.
// Java code to demonstrate the working // of floorKey() import java.io.*;
import java.util.*;
public class floorKey {
public static void main(String[] args)
{
// Declaring the tree map of Integer and String
TreeMap<Integer, String> tmp = new TreeMap<Integer, String>();
// assigning the values in the tree map
// using put()
tmp.put( 10 , "ten" );
tmp.put( 7 , "seven" );
tmp.put( 19 , "nineteen" );
tmp.put( 3 , "three" );
// use of floorKey()
// displays the floor key of
// prints 3
System.out.println( "The greatest key less than 6 is : "
+ tmp.floorKey( 6 ));
}
} |
Output:
The greatest key less than 6 is : 3
Practical Application : The possible applications of this functions are aplenty. Starting from maximum distance with given petrol or possible dishes with given ingredients. Former one is discussed in code below.
// Java code to demonstrate the application // of floorKey() and floorEntry import java.io.*;
import java.util.*;
public class floorappli {
public static void main(String[] args)
{
// Declaring the tree map of Integer and String
TreeMap<Integer, String> destin = new TreeMap<Integer, String>();
// assigning the km with destination
// from beginning
// using put()
destin.put( 10 , "Delhi" );
destin.put( 7 , "Gurgaon" );
destin.put( 19 , "Noida" );
destin.put( 3 , "Ring Road" );
// Entering the available Petrol (consider 1km/litre)
int petr = 12 ;
// Maximum place you can reach
System.out.println( "The maximum place you can reach with given petrol : "
+ destin.floorEntry(petr));
}
} |
Output:
The maximum place you can reach with given petrol : 10=Delhi