Java 8 Streams: Multiple Filters vs. Complex Condition

Under the hood: Filters & Conditions

A Peek at Performance

You need to understand method references for better coding performance. Joining up filters using these references can lead to cleaner and more efficient code. Although performance differences between employing multiple filters or bundling all conditions into a single filter are usually minimal, it's important to bear in mind the cost of creating temporary objects and the efficiency of the JVM's HotSpot optimizer in complex conditions.

There are performance improvements in later Java versions too, with Java 11 providing better stream performance, for example. So, the condition complexity and Java version are two factors to consider when choosing your filter strategy.

Readability vs Performance

Engineered for readability, multiple filters are your best friend. Using and to join predicates can be a life-saver in maintaining readability while not sacrificing too much of the performance. However, if you see that performance is taking a significant hit, it might be wiser to opt for single complex conditions, provided it doesn't turn your code into a maze that's impossible to navigate.

On most days though, readability should trump performance concerns. Good code is like good humour, it needs to be easily understood!

Evaluating with Big Data

If your code is dealing with large datasets, play safe: conduct a performance test before deciding. If the stream contains a small number of items, then multiple filters or a complex condition may not make much of a difference. But when dealing with large or complex objects, a single filter with a complex condition may be more performant.

Code Wars : Multiple Filters vs Complex Conditions

Multiple Filters: The Heroes

When dealing with decoupled logic, or when each filter can standalone, use multiple filters. They are also particularly useful when incremental filtering is required.

list.stream()
    .filter(item -> item.conditionA()) // Filter A, giving first judgment
    .filter(item -> item.conditionB()) // Filter B, making the final call
    .collect(Collectors.toList());
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In situations where you are working with parallel streams, multiple filters can turn out to be more efficient. However, do apply wisdom when slapping filters before going parallel. Too many cooks (filters) may spoil the broth (performance).

Complex Conditions: The Champs

Complex conditions excel in scenarios where the logic is interdependent or where achieving superior performance is a must. When conditions are tightly coupled, there's less journeying up and down the data pipeline if we use complex conditions. However, make sure the benefits are worth the additional complexity.

In simpler parallel streams, a single filter results in less thread contention.

list.stream()
    .filter(item -> item.conditionA() && item.conditionB()) // Checking A and B in one shot
    .collect(Collectors.toList());
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