Java 8 Streams API: Laziness and Performance Optimization

We have had a quick overview of the Java 8 Streams API in our prevous post. We looked into the power and simplicity of the Java 8 Streams API, the Intermediate and the Terminal Operations over the streams, and different ways to build streams (e.g. from collections or numerical ranges, etc.). In continuation of the same discussion, in this post, we will move ahead with the streams and have a look at the most important property of Java 8 Streams — laziness. If you are new to the concept of Java 8 streams, please go back and read Understanding Java 8 Streams API.

Laziness Improves Performance?

This is a really tricky question. If the laziness is utilized in the correct manner, the answer is 'yes.' Consider you are on an online shopping site and you searched for a particular type of a product. Usually, most of the websites will show the matching products immediately and a 'loading more' message at the bottom. Finally, all of the search results will be loaded in parts, as described. The intent behind doing this is to keep the user interested by immediately showing him some of the results. While the user is browsing through the loaded products, the rest of the products are being loaded. This is because the site is delaying the complete loading of the entire product list. Consider, if the site does eager loading or early loading of all of the products, the response time would increase and the user might get distracted to something else.

While you are dealing with bigger data or infinite streams, the laziness is a real boon. When the data is processed, we are not sure how the processed data will be used. The eager processing will always process the entire amount of data at the cost of performance and the client might end up utilizing a very small chunk of it. Or, depending upon some condition, the client may not even need to utilize that data. The lazy processing is based on a 'process-only, on-demand' strategy.

Laziness and Java 8 Streams

The current trends are all about big data, parallel processing, and being in real time. A large number of systems are being re-designed to sustain the future challenges of the consistently growing amount of data and high expectations of the performance and scalability. No wonder, if the processing model of the Java Collections API is being empowered in order to meet the future expectations, the Java 8 Streams API is fully based on the 'process-only, on-demand' strategy and, hence, supports laziness. 

In the Java 8 Streams API, the intermediate operations are lazy and their internal processing model is optimized to make it capable of being processed with a large amount of data and high performance.

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