HashMapSortingByValues.java

package com.dojo.java8.tutorials.hashmap;

import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.stream.Collectors;

public class HashMapSortingByValues {

	public static void main(String[] args) {
		// create the map of primitives
		HashMap<Integer, String> empIdVsName = new HashMap<>();
		empIdVsName.put(99, "Tom");
		empIdVsName.put(5, "Abby");
		empIdVsName.put(2, "Sam");
		empIdVsName.put(3, "Roger");
		empIdVsName.put(7, "Tim");
		//empIdVsName.put(null, "Harry");

		System.out.println("default output: " + empIdVsName);
		// sorted api- make use of Map.Entry.comparingByValue
		LinkedHashMap<Integer, String> empIdVsName_sorted = empIdVsName
				.entrySet()
				.stream()
				.sorted(Map.Entry.comparingByValue())
				.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, 
						(oldValue, newValue) -> oldValue, LinkedHashMap::new));

		System.out.println("sorted by values in asc order: " + empIdVsName_sorted);

		empIdVsName_sorted = empIdVsName
				.entrySet()
				.stream()
				.sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
				.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, 
						(oldValue, newValue) -> oldValue, LinkedHashMap::new));

		System.out.println("sorted by values in desc order: " + empIdVsName_sorted);
	}
	
	//output
	//default output: {2=Sam, 99=Tom, 3=Roger, 5=Abby, 7=Tim}
	//sorted by values in asc order: {5=Abby, 3=Roger, 2=Sam, 7=Tim, 99=Tom}
	//sorted by values in desc order: {99=Tom, 7=Tim, 2=Sam, 3=Roger, 5=Abby}
}