Motivation:
allLeaks is to store the DefaultResourceLeak. When we actually use it, the key is DefaultResourceLeak, and the value is actually a meaningless value.
We only care about the keys of allLeaks and don't care about the values. So Set is more in line with this scenario.
Using Set as a container is more consistent with the definition of a container than Map.
Modification:
Replace allLeaks with set. Create a thread-safe set using 'Collections.newSetFromMap(new ConcurrentHashMap<DefaultResourceLeak<?>, Boolean>()).'
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