The "Leaking WeakHashMap" canned analysis in the NetBeans Profiler, applied to a heap dump made of the NB IDE, turned up (among other violations):

MappedMXBeanType.convertedTypes: java.util.WeakHashMap#103 is wrong: key java.lang.Class#10232 is reachable from value sun.management.MappedMXBeanType$CompositeDataMXBeanType#1

Indeed, MappedMXBeanType.convertedTypes is a WeakHashMap, yet all of the possible value types refer strongly (in fact directly, field 'javaType') to the key type (Class). Since the map is static, if getMappedType is ever called on a class loaded by some user ClassLoader, that loader (including all of its classes and their static fields) will never be collectible.