RFR: 8282178: Replace simple iterations of Map.entrySet with Map.forEach calls

[liach]

On Wed, 23 Feb 2022 22:33:42 GMT, liach <duke at openjdk.java.net> wrote:

> Replaces simple `for (Map.Entry<K, V> entry : map.entrySet())` with `map.forEach((k, v) ->)` calls. This change is better for thread-safety and reduces allocation for some map implementations.
> 
> A more in-depth description of benefits is available at https://mail.openjdk.java.net/pipermail/core-libs-dev/2022-February/086201.html and at the JBS issue itself.
> 
> A [jmh comparison](https://jmh.morethan.io/?sources=https://gist.githubusercontent.com/liach/0c0f79f0c0b9b78f474d65cda2c5f7b5/raw/4f2a160c51164aefdfac6ab5a19bdbc8c65f5fcf/base-results.json,https://gist.githubusercontent.com/liach/0c0f79f0c0b9b78f474d65cda2c5f7b5/raw/4f2a160c51164aefdfac6ab5a19bdbc8c65f5fcf/head-results.json) on the performance of the existing `HashMapBench` shows that the performance of `putAll` for `HashMap` has not significantly changed.

In a short summary, on mailing list, stuart says this doesn't benefit concurrent maps; Remi proposed to deprecate the synchronized collections for the peculiarities of iteration; kevin said that this change improves code clarity.

Hence, I still believe changing to foreach calls in putAll can potentially benefit adding from maps that have expensive iterators and entry wrappers.

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PR: https://git.openjdk.java.net/jdk/pull/7601