Is instanceof Really Slow? A Performance Benchmark in Java 1.8

Performance Impact of Using instanceof in Java

Despite its detractors in object-oriented design, the instanceof operator remains a common design choice in applications. While its performance remains a concern, its impact is often debated. To shed light on this topic, a thorough benchmark analysis was conducted.

Benchmark Implementation

A benchmark program was created to evaluate the performance of four different implementations:

• instanceof implementation (as the reference)
• Object-oriented (abstract class with overridden method)
• Custom type implementation
• getClass() == _.class implementation

Results

After 10,000 iterations with 10 forks, the following average times were recorded:

Operation	Runtime in nanoseconds per operation	Relative to instanceof
INSTANCEOF	39,598	100.00%
GETCLASS	39,687	100.22%
TYPE	46,295	116.91%
OO	48,078	121.42%

Analysis

• instanceof and getClass() have negligible performance differences, indicating that instanceof does not incur a significant overhead.
• Using custom type IDs resulted in a moderate performance penalty compared to instanceof.
• The object-oriented approach was the slowest, although the difference was not substantial.

Conclusion

In Java 1.8, the instanceof operator is the fastest option for type checking. It is slightly faster than getClass() and significantly faster than custom type IDs or the object-oriented approach. Given its minimal performance impact, instanceof remains a viable choice for type checking in performance-critical scenarios.

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