Tracking down a leak in my application I found that tens of thousands of BindingHelperObserver and WeakReference objcts were accumulating, all rooted in an indeterminate ProgressBar that wasn't even visible.

Using jvisualvm to compare heap dumps at various points (after forcing GC), I see the following chain of objects:

WeakReference
BindingHelperObserver
InvalidationListener[]
ExpressionHelper$Generic
Node$NodeTransformation$2
Node$NodeTransformation
StackPane
ProgressBarSkin
ProgressBar

or

WeakReference
BindingHelperObserver
InvalidationListener[]
ExpressionHelper$Generic
ProgressBarSkin$1
ProgressBarSkin
ProgressBar


(The one with the NodeTransformation appears to be related to the animated style of the indeterminate ProgressBar.)

After changing my application to force the invisible progress bar to have a progress value of 0.0 (it was initially left at the default of -1.0), I could no longer reproduce the leak.