Скачать или смотреть How to Elegantly Handle Empty Lists in Java 8 Using Lambdas java, lambda, java-stream

Discover how to simplify your Java 8 code by gracefully handling empty lists with lambdas. Learn the elegant solution in just one line!
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This video is based on the question https://stackoverflow.com/q/63385900/ asked by the user 'user1748379' ( https://stackoverflow.com/u/1748379/ ) and on the answer https://stackoverflow.com/a/63386288/ provided by the user 'Bohemian' ( https://stackoverflow.com/u/256196/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling Empty Lists in Java 8 Laminas

In Java programming, particularly when working with collections, one common pitfall is dealing with empty lists. Attempting to operate on an empty list often leads to run-time errors, which can halt your program and create frustrating debugging sessions. This blog aims to present an elegant, compact solution for handling empty lists when using Java 8 and lambdas.

The Challenge

Consider the following Java code snippet:

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

Here, we fetch a list of Model1 objects from the data access object (dao) and then convert it to a list of Model2 objects. If list1 is empty, it throws an exception, resulting in an undesirable error state. The goal is to combine lines 2 and 3 into a single, elegant line that maintains the same functionality while gracefully handling the empty list scenario.

The Solution

Using Optional in Java provides a powerful way to deal with potentially absent values in a cleaner manner. Below, we will refine the original code into a more concise single line.

Step-by-Step Breakdown

The solution is to wrap the list in an Optional and filter it based on its non-empty condition. Here's how we can do this:

Wrap the List in an Optional: This provides a container that may or may not hold a non-empty value.

Filter the List: Check if the list is not empty using !isEmpty(). If it is empty, it will trigger an exception.

Stream and Map: If the list is valid, we can convert it to the desired type using the map function.

Here's the elegant one-liner that effectively implements this logic:

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

Explanation of the Code

Optional.of(dao.list()): Creates an Optional from the list fetched from dao.

.filter(c -> !c.isEmpty()): Filters out the empty lists, allowing for a graceful exception if it fails the check.

.orElseThrow(Exception::new): Throws an exception if the list is empty.

.stream(): Initiates a stream to allow method chaining for further operations.

.map(this::buildModel2): Transforms each Model1 object into a Model2 object.

.collect(toList()): Collects the transformed objects into a new list.

Conclusion

By utilizing Java 8’s Optional, you can avoid the run-time errors associated with empty lists while maintaining clear and concise code. This approach not only enhances readability but also keeps your codebase elegant and manageable. Whether you're a seasoned Java developer or just starting, mastering such patterns will significantly improve your ability to handle collections in a streamlined fashion.

Take advantage of this powerful feature in Java 8 and elevate your coding practices!