How to Create a List with Multiple Properties Using Java Streams

Discover how to efficiently convert entities from one structure to another in Java using Stream API without nested loops.
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How to Create a List with Multiple Properties Using Java Streams

When working with complex data structures in Java, such as custom classes and nested properties, transforming these entities can sometimes present a challenge. In this guide, we will explore how to convert an entity of type P into a structured list of OrderLi using Java Streams.

Understanding the Problem

You have a class structure that consists of several nested classes, specifically:

Class P that contains a list of Lin

Class Lin that holds an object of type Oh and two lists: one for Pr and another for Qty

Class Oh, representing properties related to order data

Your goal is to convert the data structure from the P class into a list of OrderLi, which combines properties from the Oh and directly maps the lists from Lin.

Below is a brief outline of the involved classes:

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

The Challenge

Your challenge involves transforming the instances of Lin to instances of OrderLi without using nested loops. The objective is to create a more streamlined and readable codebase by utilizing Java's powerful Stream API.

Solution: Using Java Stream API

Here's a concise and effective way to perform the transformation with Java Streams. Below is the provided code that does exactly this:

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

Breakdown of the Code

Stream the List: Convert the list of Lin into a Stream with .stream().

Map Transformation: Use the .map() function to transform each Lin into a new OrderLi instance.

Get ohId and size from the Oh object, providing default values if necessary.

The lists for pr and qty are directly accessed from the Lin object.

Advantages of This Approach

Clean and Readable: The use of Streams results in more succinct and maintainable code.

Avoids Nested Loops: By leveraging map transformations, we eliminate the need for multiple looping constructs, enhancing performance.

Safe Null Handling: The Optional class helps mitigate null issues effectively.

Conclusion

Transforming complex nested structures into more useful formats can be streamlined significantly with Java Stream API. Not only does this approach keep your code clean, but it also enhances readability and debugging.

With this guide, you should now be able to convert entities from one structure to another with ease, while taking full advantage of Java's functional programming capabilities.

If you have any questions or need further examples, feel free to reach out!