Reduce a List of Nested Objects into a Map Using Java 8 Streams

Discover how to efficiently reduce a list of nested objects into a Map in Java 8 Streams. Learn step-by-step solutions and practical tips!
---
This video is based on the question https://stackoverflow.com/q/66544780/ asked by the user 'coder Tester' ( https://stackoverflow.com/u/9649220/ ) and on the answer https://stackoverflow.com/a/66546836/ provided by the user 'ETO' ( https://stackoverflow.com/u/10584605/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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: How to reduce a list of nested objects into a Map

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Reduce a List of Nested Objects into a Map Using Java 8 Streams

In the world of programming, particularly with Java, you may find yourself dealing with complex data structures. One such common scenario is when you have a list of nested objects, and you need to derive meaningful information from them. In this guide, we will navigate through the task of reducing a list of nested objects into a Map using Java 8 Streams.

Understanding the Problem

Imagine you are handling an e-commerce application. You have classes representing Customers, Orders, and Products. Your goal is to find out which customer has spent the most money on orders. Sounds intriguing, right?

Below is a condensed view of the classes we will deal with:

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

Given a list of orders and their respective data, we want to create a Map<Customer, BigDecimal>, where each entry represents a customer and the total amount they have spent. Let’s break down the solution into manageable steps.

Step-by-Step Solution

Step 1: Calculate the Price of an Order Line

The first thing we need is a method to calculate the total price of an OrderLine, which considers both the product's price and its quantity:

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

Step 2: Calculate Total Price of an Order

Next, we need to derive the total price for an entire Order by summing the prices of all its order lines:

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

Step 3: Calculate Total Money Spent Per Customer

Now that we have the total price of each order, we can proceed to create a map that reflects the total money spent by each customer:

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

Step 4: Identify the Customer Who Spent the Most

With a map in hand, we now want to find out which customer has contributed the most money:

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

Keep in mind that topCustomer may be empty if the list of orders happens to be void.

Conclusion

Congratulations! You have successfully learned how to reduce a list of nested objects into a map using Java 8 Streams. By following these structured steps, you can easily analyze overlapping data structures and derive insightful conclusions.

If you have any questions or need clarification on any steps, feel free to drop a comment below! Happy coding!

Видео Reduce a List of Nested Objects into a Map Using Java 8 Streams канала vlogize