Program: How to get sorted sub-map from TreeMap?

Below example shows how to get range of elements from sorted user defined objects by using comparator object. You can include you own custom sorting logic with compare method. By passing comparator object to the TreeMap, you can sort the keys based on the logic provided inside the compare method. Once the keys are sorted, you can call subMap() method to get range of elements based on key.

package com.java2novice.treemap;

import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;

public class MySubTreeMap {
	
	public static void main(String a[]){
		//the treemap sorts by key
		TreeMap<String, String> hm = new TreeMap<String, String>(new MyCompr());
		//add key-value pair to TreeMap
		hm.put("java", "language");
		hm.put("computer", "machine");
		hm.put("india","country");
		hm.put("mango","fruit");
		hm.put("game","cricket");
		System.out.println("TreeMap Entries:");
		System.out.println(hm);
		Map<String, String> subMap1 = hm.subMap("game", "java");
		System.out.println("Sub-Map enties:");
		System.out.println(subMap1);
		//how to get lower boundary also part of sub-map
		Map<String, String> subMap2 = hm.subMap("game", true, "java", true);
		System.out.println("Sub-Map enties:");
		System.out.println(subMap2);
		//how to omit upper boundary in the sub-map
		Map<String, String> subMap3 = hm.subMap("game", false, "java", true);
		System.out.println("Sub-Map enties:");
		System.out.println(subMap3);
	}
}

class MyCompr implements Comparator<String>{

	@Override
	public int compare(String str1, String str2) {
		return str1.compareTo(str2);
	}
	
}

TreeMap Entries:
{computer=machine, game=cricket, india=country, java=language, mango=fruit}
Sub-Map enties:
{game=cricket, india=country}
Sub-Map enties:
{game=cricket, india=country, java=language}
Sub-Map enties:
{india=country, java=language}