Java Basic Tutorial

Java Flow Control

Java Array

Java Object-Oriented (I)

Java Object-Oriented (II)

Java Object-Oriented (III)

Java Exception Handling

Java List

Java Queue (Queue)

Java Map Collection

Java Set Collection

Java Input/Output (I/O)

Java Reader/Writer

Java other topics

Java Method Overloading Comprehensive Java Examples

Java program to sort a map by value

Comprehensive Java Examples

In this program, you will learn how to sort a given mapping by value in Java.

Example: Sort map by value

import java.util.*;
public class SortMap {
　　　　public static void main(String[] args) {
　　　　　　　　LinkedHashMap<String, String> capitals = new LinkedHashMap<>();
　　　　　　　　capitals.put("Nepal", "Kathmandu");
　　　　　　　　capitals.put("India", "New Delhi");
　　　　　　　　capitals.put("United States", "Washington");
　　　　　　　　capitals.put("England", "London");
　　　　　　　　capitals.put("Australia", "Canberra");
　　　　　　　　Map<String, String> result = sortMap(capitals);
　　　　　　　　for (Map.Entry<String, String> entry : result.entrySet())
　　　　　　　　{
　　　　　　　　　　　　System.out.print("Key: ",　+　entry.getKey());
　　　　　　　　　　　　System.out.println(" Value: ",　+　entry.getValue());
　　　　　　　　}
　　　　}
　　　　public static LinkedHashMap<String, String> sortMap(LinkedHashMap<String, String> map) {
　　　　　　　　List<Map.Entry<String, String>> capitalList = new LinkedList<>(map.entrySet());
　　　　　　　　Collections.sort(capitalList, (o1, o2)　-> o1.getValue().compareTo(o2);
　　　　　　　　LinkedHashMap<String, String> result = new LinkedHashMap<>();
　　　　　　　　for (Map.Entry<String, String> entry : capitalList)
　　　　　　　　{
　　　　　　　　　　　　result.put(entry.getKey(), entry.getValue());
　　　　　　　　}
　　　　　　　　return result;
　　　　}
}

When running the program, the output is:

Key: Australia Value: Canberra
Key: Nepal Value: Kathmandu
Key: England Value: London
Key: India Value: New Delhi
Key: United States Value: Washington

In the above program, we convert the LinkedHashMap country/The regions and their respective capitals are stored in the variable capitals.

We have a method sortMap() that takes a doubly linked list and returns a sorted doubly linked list.

Within the method, we convert the hash map to a list capitalList. Then, we use the sort() method, which accepts a list and a comparator.

In our instance, the comparator is (o1,o2)-> o1.getValue().compareTo(o2.getValue()) two lists o1and o2lambda expression for comparing the values.

After the operation, we get the sorted list capitalList. Then, we simply convert the list to a LinkedHashMap result and return it.

Returning to the main() method, we iterate over each item in the map and print its key and value.

Comprehensive Java Examples

Java Method Overloading Comprehensive Java Examples