Java 8 Streams: Multiple Filters vs. Complex Conditions: Which Performs Better?

Java 8 Streams: Performance of Multiple Filters vs. Complex Conditions

In Java 8, streams offer powerful filtering capabilities. When filtering with multiple conditions, the developer has the option to use multiple filter() operations or a single filter() operation with a complex condition. The question arises: which approach is better for performance?

Multiple Filter Operations

Using multiple filter() operations allows for straightforward and readable code, as demonstrated below:

<code class="java">myList.stream()
    .filter(x -> x.size() > 10)
    .filter(x -> x.isCool())
    ...</code>

Complex Condition

Alternatively, a single filter() operation can be utilized with a complex condition:

<code class="java">myList.stream()
    .filter(x -> x.size() > 10 && x.isCool())
    ...</code>

Performance Comparison

Intuitively, it may seem that the complex condition approach would be more efficient due to its use of a single filter(). However, the reality is not so straightforward.

Hotspot Optimization

The Java Hotspot compiler optimizes code, including stream operations. As such, the underlying code generated for both approaches is highly similar. The performance characteristics are therefore not significantly different.

Object Creation and Method References

Using multiple filter() operations creates more objects and delegating code than using a single filter() operation with a complex condition. However, if method references are used instead of lambda expressions, this overhead can be minimized.

Parallelism

Theoretically, multiple filters could be parallelizable to a greater extent than a single filter. However, this advantage is only relevant for compute-intensive operations and requires a specific implementation that supports parallel processing of subsequent stages.

Conclusion

In practice, there is no clear performance benefit to using either multiple filter() operations or a complex condition. The choice should be guided by readability and the specific context of the code. For complex conditions that are difficult to express with multiple filters, the complex condition approach may be preferred. However, for simple conditions, multiple filters may be more straightforward and maintainable.

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