jp-baos-tobytearray-copy
Claim
ByteArrayOutputStream.toByteArray() copies; prefer writeTo(out) on a reused BAOS.
How measured
- Source:
J32_RuleEvidenceBatch.jsonl - JDK 27 (27+35), JVM args
-XX:+UseCompactObjectHeaders - before:
toByteArray_4k - after:
writeTo_reuse
Runtime (this evidence file)
| Field | Value |
|---|---|
| When | 2026-10-23 Asia/Shanghai |
| before | 13982.720 ns_per_op, 8224.210 B/op |
| after | 140.556 ns_per_op, 0.002 B/op |
| ratio before/after | ~99.5× |
Lint mapping / policy
Policy error (~99×).
Limits
Microbench on this machine; see scripts/run-static-vs-hotspot.sh. Do not invent ratios. Corpus residual ≠ speedup.