Write a Java program to get the portion of a map whose keys are strictly less than a given key

The program creates a TreeMap object named s1 and adds some key-value pairs to it. Then, it prints out a portion of the TreeMap based on the specified keys using the headMap() method.

The headMap() method returns a view of the portion of the map whose keys are strictly less than the specified key. In this program, the first headMap() method call returns all the key-value pairs whose keys are less than 101, the second headMap() method call returns all the key-value pairs whose keys are less than 103, and the third headMap() method call returns all the key-value pairs in the TreeMap since the key 107 is greater than the greatest key in the TreeMap.

Source Code

import java.util.*;
import java.util.Map.Entry;  
public class GetPortion
{  
	public static void main(String args[])
	{		
		TreeMap<Integer,String> s1 = new TreeMap<Integer,String>();
		s1.put(101, "Joes");
		s1.put(102, "Charles");		
		s1.put(103, "John");
		s1.put(104, "George");
		s1.put(105, "Smith");
 
		System.out.println("Given TreeMap : " + s1);
		System.out.println("Checking the 101 Key(s): " + s1.headMap(101));
		System.out.println("Checking the 103 Key(s): " + s1.headMap(103));
		System.out.println("Checking the 107 Key(s): " + s1.headMap(107));
	}
}

Output

Given TreeMap : {101=Joes, 102=Charles, 103=John, 104=George, 105=Smith}
Checking the 101 Key(s): {}
Checking the 103 Key(s): {101=Joes, 102=Charles}
Checking the 107 Key(s): {101=Joes, 102=Charles, 103=John, 104=George, 105=Smith}