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 floorEntryimport 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
