Does Using the `final` Keyword in Java Impact Performance?

Performance Implications of the Final Keyword in Java

Despite the widespread availability of the final keyword in Java, its use remains relatively uncommon. This article explores whether the use of final in specific scenarios, such as method override prevention and class inheritance prohibition, has performance implications.

Virtual Method Optimization

Generally, using final for virtual methods (methods that can be overridden) does not significantly impact performance. HotSpot, the most popular Java Virtual Machine, monitors method overrides and optimizes executions based on the assumption that non-final methods have not been overridden. When an override is detected, HotSpot can adjust optimizations accordingly.

Design and Readability over Performance

The decision to use final should primarily consider design clarity and readability rather than performance. Performance optimization should be based on actual measurements and not solely on the use of final. In most cases, achieving extra performance by altering code structure compromises readability and design, and the benefits seldom outweigh the drawbacks.

Final Fields for Cross-Thread Visibility

Using final for fields has design advantages beyond performance. Final fields ensure that their values are visible immediately in other threads after a constructor completes. This enhanced inter-thread visibility makes final fields a common practice, especially in multithreaded environments.

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