On Wed, 11 Feb 2026 13:47:17 GMT, jengebr <[email protected]> wrote: >> src/java.base/share/classes/java/util/HashMap.java line 516: >> >>> 514: */ >>> 515: final void putMapEntries(Map<? extends K, ? extends V> m, boolean >>> evict) { >>> 516: if (m.getClass() == Collections.UnmodifiableMap.class) { >> >> I would address that issue in a separate bug. > > What issue? This is an integral part of the performance optimization.
Your PR proposes two optimizations, - HashMap.putAll(HashMap) - HashMap.putAll(UnmodifiableMap(HashMap)) The former have been done numerous time for other collections, the latter is as far as as know new. There are several reasons to not wanting to do the latter , on top of my head: - this is not a symmetrical transformation, - why only have this optimization on HashMap and not ArrayList and/or ArrayDeque ? So It's a separate issue that should be discussed on on the mailist list first. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/28243#discussion_r2794933915
