Java(TM) 2 Runtime Environment, Standard Edition (build
1.4.0-beta_refresh-b72)
Java HotSpot(TM) Client VM (build 1.4.0-beta_refresh-b72, mixed mode)

Run hprof against on any simple class (HelloWorld.java) and analyze the heap dump. You will find that some objects in the heap dump have no referrers at all. When I say that some objects have no referrers, I mean that there are no objects in the heap dump referencing them. My understanding is that the heap dump should only contain live objects, therefore all objects should have at least one reference to them.

Profiling a simple "Hello World" Java program will illustrate the problem.
I've also attached output from hprof that illustrates the problem. There
are quite a few objects in the attached dump that have no referrers. For
example, look at objects:

8c3ee70
96ddc0
8c44618
8c92440
8ba1448

There is no object in the heap dump referencing them. There are more
objects with no referrers; these are just a few.

Tested with the latest build 76 (merlin-beta2 release) to see if fix for 4363856 will address this issue, but the problem still exists.

I have noticed that it's often (but not always) String objects that do not have any references to them.