RFR: 8247402: rewrite the implementation requirements for Map::compute()

[John Lin]

On Sat, 17 Oct 2020 02:40:35 GMT, John Lin <github.com+1290376+johnlinp at openjdk.org> wrote:

>> This change is to a normative portion of the specification, and as such will require a CSR.
>
> Hi @pavelrappo & @stuart-marks,
> 
> Thank you for the review. When I first proposed this patch in the mailing list, the patch looked like this:
> 
> # HG changeset patch
> # User John Lin <johnl... at gmail.com>
> # Date 1591923561 -28800
> #      Fri Jun 12 08:59:21 2020 +0800
> # Node ID 03c9b5c9e632a0d6e33a1f13c98bb3b31b1bf659
> # Parent  49a68abdb0ba68351db0f140ddac793b1c391bd5
> 8247402: Rewrite the implementation requirements for Map::compute()
> 
> diff --git a/src/java.base/share/classes/java/util/Map.java
> b/src/java.base/share/classes/java/util/Map.java
> --- a/src/java.base/share/classes/java/util/Map.java
> +++ b/src/java.base/share/classes/java/util/Map.java
> @@ -1113,17 +1113,12 @@ public interface Map<K, V> {
>       * <pre> {@code
>       * V oldValue = map.get(key);
>       * V newValue = remappingFunction.apply(key, oldValue);
> -     * if (oldValue != null) {
> -     *    if (newValue != null)
> -     *       map.put(key, newValue);
> -     *    else
> -     *       map.remove(key);
> -     * } else {
> -     *    if (newValue != null)
> -     *       map.put(key, newValue);
> -     *    else
> -     *       return null;
> +     * if (newValue != null) {
> +     *     map.put(key, newValue);
> +     * } else if (oldValue != null) {
> +     *     map.remove(key);
>       * }
> +     * return newValue;
>       * }</pre>
>       *
>       * <p>The default implementation makes no guarantees about detecting if the
> 
> which didn't change the pseudo-code implementation.
> 
> However, Martin Buchholz reviewed my patch and suggested me to modify it to match the real implementation in HashMap:
> https://www.mail-archive.com/core-libs-dev@openjdk.java.net/msg66197.html
> https://www.mail-archive.com/core-libs-dev@openjdk.java.net/msg66199.html
> https://www.mail-archive.com/core-libs-dev@openjdk.java.net/msg66210.html
> Therefore, I modified my patch and submitted it in the original mailing list and in this PR.
> 
> I don't think creating a CSR is in the scope of JDK-8247402. I'll create another PR with my original patch. Thanks.

I've created https://github.com/openjdk/jdk/pull/714.

-------------

PR: https://git.openjdk.java.net/jdk/pull/451