Effortless Java Map Sorting: Mastering Lambda Expressions

Unlock the Power of Java Maps: Sorting Values with Ease

When working with Java maps, one common challenge is sorting the values in a specific order. Fortunately, with the right techniques, you can master this task and take your coding skills to the next level.

The Problem: Unsorted Maps

Imagine you have a map that stores countries and their respective capitals. Without proper sorting, the output can be confusing and difficult to work with. That’s where the LinkedHashMap comes in – a powerful tool that allows you to sort your map by values.

The Solution: Sorting with Lambda Expressions

To sort a map by values, you need to create a custom method that takes the map as an input and returns a sorted map. This is where the sortMap() method comes into play. Inside this method, you create a list from the map values and use the sort() method of Collections to sort the elements.

The Magic of Lambda Expressions

The key to successful sorting lies in the lambda expression used as a comparator. This expression takes two adjacent elements of the list, extracts their values using the getValue() method, and compares them using the compareTo() method. The result is a sorted list that can be easily converted back into a LinkedHashMap.

Putting it all Together

In the main() method, you can loop through each item in the sorted map and print its key and value. The output will be a beautifully sorted list of countries and their capitals.

Code in Action

Here’s the complete code example:
“`
public class SortMap {
public static void main(String[] args) {
// Create a LinkedHashMap named capitals
LinkedHashMap capitals = new LinkedHashMap<>();
capitals.put(“USA”, “Washington D.C.”);
capitals.put(“France”, “Paris”);
capitals.put(“Japan”, “Tokyo”);

    // Sort the map by values
    LinkedHashMap<String, String> sortedCapitals = sortMap(capitals);

    // Print the sorted map
    for (Map.Entry<String, String> entry : sortedCapitals.entrySet()) {
        System.out.println(entry.getKey() + ": " + entry.getValue());
    }
}

public static LinkedHashMap<String, String> sortMap(LinkedHashMap<String, String> map) {
    List<Map.Entry<String, String>> capitalList = new ArrayList<>(map.entrySet());
    Collections.sort(capitalList, (l1, l2) -> l1.getValue().compareTo(l2.getValue()));
    LinkedHashMap<String, String> result = new LinkedHashMap<>();
    for (Map.Entry<String, String> entry : capitalList) {
        result.put(entry.getKey(), entry.getValue());
    }
    return result;
}

}
“`
With this code, you’ll be able to sort your maps by values in no time!