On Tue, 29 Jun 2021 19:23:26 GMT, Roger Riggs <rri...@openjdk.org> wrote:
>> src/java.base/share/classes/java/lang/System.java line 337: >> >>> 335: = Collections.synchronizedMap(new WeakHashMap<>()); >>> 336: } >>> 337: >> >> I wonder about the use of a WeakHashMap here. That may work well when the >> source is an interned string (a class name) which will be strongly >> referenced elsewhere and may be garbage collected if the class is unloaded, >> but in the case where it contains the name of the source jar then that >> string will only be referenced by the weak hashmap, and therefore it could >> be garbage collected any time - which would cause the mapping to be removed. >> In that case you cannot guarantee that the warning will be emitted only once. > > Using a HashSet<Class> could use the callerClass as the key and be a stable > reference for having given the message. > or use a ConcurrentHashMap<Class<?>>, boolean> and avoid any separate > synchronization that would be needed with a HashSet or HashMap. If I switch to a "non-weak" set or map, then it seems I can safely use the source string as the key. Will using the Class object as a key prevent them from unloading? ------------- PR: https://git.openjdk.java.net/jdk17/pull/166
