Reduce memory overhead caused by default collection sizes

[Legioth]

There are various collections that are usually not used at all or with
only a small number of items. Allocating the default sizes for such
collections wastes quite some memory: HashSet and HashMap allocate for
16 items by default, ArrayList for 10 items and IdentityHashMap for 32.

Reduces BasicElementView memory use from 429706 to 419682 bytes and the
memory use in BeverageBuddy with an edit dialog open from 262257 to
251569 bytes.

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This change is 

[caalador]

Reviewed 5 of 5 files at r1.
Reviewable status: all discussions resolved, 0 of 1 LGTMs obtained, and 1 stale

[pekam]

Reviewed 4 of 5 files at r1.
Reviewable status: 2 unresolved discussions, 1 of 1 LGTMs obtained

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flow-server/src/main/java/com/vaadin/flow/component/ComponentEventBus.java, line 155 at r1 (raw file):

        }

        componentEventData.computeIfAbsent(eventType, t -> new ArrayList<>())

This ArrayList could also have initial capacity.
Most commonly it will contain only one item, since it's rare to add multiple listeners for the same event type.

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flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/ElementListenerMap.java, line 356 at r1 (raw file):

listeners.containsKey(eventType)

This returns always true, (because of the above listenerList != null check), so what's the point of having it in here?

assert would make more sense if you want to include this check anyway.

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flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/ElementPropertyMap.java, line 151 at r1 (raw file):

        propertyListeners.add(listener);
        return () -> propertyListeners.remove(listener);

I guess removal could also be optimized like in ElementListenerMap?

But that's not as common case, with not as big benefits, so not blocking.

[Legioth]

Reviewable status: 2 unresolved discussions, 0 of 1 LGTMs obtained, and 1 stale

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flow-server/src/main/java/com/vaadin/flow/component/ComponentEventBus.java, line 155 at r1 (raw file):

Previously, pekam (Pekka Maanpää) wrote…

This ArrayList could also have initial capacity.
Most commonly it will contain only one item, since it's rare to add multiple listeners for the same event type.

Done.

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flow-server/src/main/java/com/vaadin/flow/internal/nodefeature/ElementListenerMap.java, line 356 at r1 (raw file):

Previously, pekam (Pekka Maanpää) wrote…

listeners.containsKey(eventType)

This returns always true, (because of the above listenerList != null check), so what's the point of having it in here?

assert would make more sense if you want to include this check anyway.

Done.

[vaadin-bot]

SonarQube analysis reported 5 issues

Note: The following issues were found on lines that were not modified in the pull request. Because these issues can't be reported as line comments, they are summarized here:

1. Binder.java#L765: Remove usage of generic wildcard type.
2. ElementListenerMap.java#L386: Rename "listeners" which hides the field declared at line 59.
3. Binder.java#L709: "public" is redundant in this context.
4. ComponentEventBus.java#L202: Remove useless curly braces around statement
5. ElementListenerMap.java#L344: Move this method into "DomEventListenerWrapper".

[pekam]

Reviewed 2 of 2 files at r2.
Reviewable status: all discussions resolved, 0 of 1 LGTMs obtained, and 2 stale