FULL PRODUCT VERSION :
java version "1.6.0_02"
Java(TM) SE Runtime Environment (build 1.6.0_02-b05)
Java HotSpot(TM) Client VM (build 1.6.0_02-b05, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
JTree isExpanded(TreePath) is unnecessarily recursive. With the default stack size (or any reasonable size) a TreePath to a few thousand entries will lead to StackOverflowException. Trees are used to represent graphs, e.g., reference chains that can easily exceed this depth. isExpanded(TreePath) can be trivially rewritten as a loop.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
In a loop, lengthen a path by adding children to a branch of a tree, one per level, and keep calling isVisible() on the TreePath that represents the deepest child until you get StackOverflowException.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Some degradation in speed, but no exceptions.
ACTUAL -
StackOverflowException when isVisible(TreePath) calls isExpanded(TreePath).

REPRODUCIBILITY :
This bug can be reproduced always.