林自均, pleased to meet you!
This rewrite seems clear and clean.
Would it be even clearer if we did
if (newValue != null) {
map.put(key, newValue);
} else {
map.remove(key);
}
Hmmm, what about the corner case where the map permits null values and
the old value is null?
On Thu, Jun 11, 2020 at 7:45 PM 林自均 <johnl...@gmail.com> wrote:
>
> Hi all,
>
> This is my first time contribution. Please let me know if I did
> something wrong. Thanks. Regards
>
> I'm working on this bug: https://bugs.openjdk.java.net/browse/JDK-8247402
>
> The original problem is that the implementation requirements for
> Map::compute() lacks of return statements for some cases. However, I
> found that there are some other problems in it:
>
> 1. The indents are 3 spaces, while most of the indents are 4 spaces.
> 2. The if-else is overly complicated and can be simplified.
>
> My proposed patch that generated by `hg export -g` is:
>
> # HG changeset patch
> # User John Lin <johnl...@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
>
> Best,
> John Lin
