advanced~4h
JMH Benchmarking and Collections Performance
Why naive timing with System.currentTimeMillis() lies to you about real Java performance, how JMH (Java Microbenchmark Harness) measures correctly despite JIT warmup and dead code elimination, and what properly measured benchmarks actually reveal about ArrayList vs LinkedList and HashMap vs TreeMap -- the measurement half of a question the Collections category's 'Choosing the Right Collection' topic already answers from the choosing side.
Learning objectives
- Explain at least two specific ways a naive System.currentTimeMillis() benchmark produces a misleading result
- Explain what JIT warmup and dead code elimination are, in the specific context of why they break naive benchmarks
- Write and run a basic JMH @Benchmark method with a realistic configuration
- Interpret measured throughput and latency differences between ArrayList and LinkedList, and between HashMap and TreeMap
- Explain why this topic's focus (measuring) is distinct from the Collections category's focus (choosing)
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JMH Benchmarking and Collections Performance