Java Boxing and Unboxing: The Hidden Performance Cost
Master primitive vs object performance. Learn when autoboxing kills latency and how to avoid allocation overhead.
JOptimize Team
Autoboxing converts primitives to objects automatically. It is convenient but expensive. One Integer allocation costs 100+ nanoseconds. In tight loops this adds up to milliseconds.
When to use Integer vs int, when to use primitive collections, and optimization strategies.
One boxed Integer = 100ns per box. 1M boxes = 100ms overhead in collections.
Solutions: Use primitive collections (FastUtil IntArrayList), avoid boxing in hot loops, use IntStream instead of Stream<Integer>, leverage cached values for -128 to 127.
Trade-off: convenience vs performance. Choose based on profile data and measured allocation rates.
Production rule: Avoid autoboxing in hot paths >1000/sec. Use primitive collections for large datasets. Monitor allocation rate.
Summary: Autoboxing costs 100ns per box. Use primitive collections when performance matters.
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