Sort a Map in Java Based on Values in Decreasing Order

Learn how to sort a map in Java by its values in decreasing order using the Stream API and Comparator interface. Discover effective methods to achieve character frequency counting with clear examples.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Sort map based on values in decreasing order

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Sort a Map in Java Based on Values in Decreasing Order

Sorting data efficiently is a common operation in programming. One such task is sorting a map based on its values. In Java, sorting a map is not as straightforward as sorting an array or a list, especially when it comes to arranging the values in decreasing order. In this post, we will explore how to achieve this using the Java Stream API and the Comparator interface.

The Problem: Sorting a Map

Let's consider a common scenario where you have a string, and you want to count the frequency of each character in that string. For instance, given the string "PriyankaTaneja", you might want to create a map that counts how many times each character appears, and then sort that map by the frequency of the characters in decreasing order.

The Goal

Count the frequency of each character in the string.

Sort the map based on the frequency values such that the characters with the highest frequencies appear first.

The Solution: Using Java Stream API

To accomplish the above-stated goal, we can utilize the following steps:

Step 1: Create the Character Frequency Map

First, we need to traverse the string and populate a HashMap to store each character and its corresponding frequency. Here's how you can do that:

[[See Video to Reveal this Text or Code Snippet]]

In this code snippet:

We convert the string into a character array.

For each character, we either add it to the map with a frequency of one or increment the existing frequency.

Step 2: Sort the Map by Values

Now that we have the frequency map, the next step is to sort this map by its values in decreasing order. We can achieve this using the Java Stream API as follows:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Sorting Code:

Stream the Entry Set: We start by getting the entry set of the map and convert it into a stream.

Collecting the Results: Finally, we collect the sorted entries into a new LinkedHashMap to maintain the order.

Step 3: Display the Sorted Map

The last step is to print the sorted map to see the character frequencies in order. You can do this using:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the steps outlined above, you can easily count character frequencies from a string and sort them in decreasing order using Java's powerful Stream API. This approach is not only efficient but also leverages modern Java features for clearer and more concise code.

With this knowledge, you can tackle various problems where sorting and counting elements dynamically are necessary.

Happy coding!