// Java program to demonstrate NavigableMap 
import java.util.NavigableMap; 
import java.util.TreeMap; 

public class Example 
{ 
	public static void main(String[] args) 
	{ 
		NavigableMap<String, Integer> nm = 
						new TreeMap<String, Integer>(); 
		nm.put("C", 888); 
		nm.put("Y", 999); 
		nm.put("A", 444); 
		nm.put("T", 555); 
		nm.put("B", 666); 
		nm.put("A", 555); 

		System.out.printf("Descending Set : %s%n", 
								nm.descendingKeySet()); 
		System.out.printf("Floor Entry : %s%n", 
								nm.floorEntry("L")); 
		System.out.printf("First Entry : %s%n", 
								nm.firstEntry()); 
		System.out.printf("Last Key : %s%n", 
								nm.lastKey()); 
		System.out.printf("First Key : %s%n", 
								nm.firstKey()); 
		System.out.printf("Original Map : %s%n", nm); 
		System.out.printf("Reverse Map : %s%n", 
								nm.descendingMap()); 
	} 
} 

output:
Descending Set : [Y, T, C, B, A]
Floor Entry : C=888
First Entry : A=555
Last Key : Y
First Key : A
Original Map : {A=555, B=666, C=888, T=555, Y=999}
Reverse Map : {Y=999, T=555, C=888, B=666, A=555}