Name: krC82822 Date: 02/14/2001


java version "1.3.0_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0_01)
Java HotSpot(TM) Client VM (build 1.3.0_01, mixed mode)

When our application starts up, its display contains an empty JTree, that is a
tree with no nodes. Its TreeModel is null. This is perfectly valid, and causes
no problems in normal use.
We are using a test tool that relies on the accessibility features to discover
the GUI component hierarchy, in the same way as the Monkey program from the
Accessibility toolkit. When we invoke Monkey's "refresh trees" function and an
empty tree is showing, it fails with a NullPointerException, like this:

java.lang.NullPointerException:
at javax.swing.JTree$AccessibleJTree.<init>(JTree.java:3247)
at javax.swing.JTree.getAccessibleContext(JTree.java:3221)
at ComponentNode.<init>(ComponentNode.java:53)
at Monkey.addComponentNodes(Monkey.java:153)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.addComponentNodes(Monkey.java:158)
at Monkey.createComponentTree(Monkey.java:197)
at Monkey.refreshTrees(Monkey.java:94)
at Monkey$1.actionPerformed(Monkey.java:118)
at javax.swing.AbstractButton.fireActionPerformed
(AbstractButton.java:1450)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed
(AbstractButton.java:1504)
at javax.swing.DefaultButtonModel.fireActionPerformed
(DefaultButtonModel.java:378)
at javax.swing.DefaultButtonModel.setPressed
(DefaultButtonModel.java:250)
at javax.swing.AbstractButton.doClick(AbstractButton.java:279)
at
javax.swing.plaf.basic.BasicMenuItemUI$MouseInputHandler.mouseReleased
(BasicMenuItemUI.java:886)
at java.awt.Component.processMouseEvent(Component.java:3717)
at java.awt.Component.processEvent(Component.java:3546)
at java.awt.Container.processEvent(Container.java:1164)
at java.awt.Component.dispatchEventImpl(Component.java:2595)
at java.awt.Container.dispatchEventImpl(Container.java:1213)
at java.awt.Component.dispatchEvent(Component.java:2499)
at java.awt.LightweightDispatcher.retargetMouseEvent
(Container.java:2451)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2216)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2125)
at java.awt.Container.dispatchEventImpl(Container.java:1200)
at java.awt.Window.dispatchEventImpl(Window.java:912)
at java.awt.Component.dispatchEvent(Component.java:2499)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:319)
at java.awt.EventDispatchThread.pumpOneEvent
(EventDispatchThread.java:103)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:84)

The constructor for AccessibleJTree does not cater for the tree model to be
null, although other parts of JTree (notably setModel()) make explicit checks
for this. Line 3247 in JTree.java, in the constructor for AccessibleJTree,
needs to be changed from this:

            JTree.this.getModel().addTreeModelListener(this);

to this:

            TreeModel treeModel = JTree.this.getModel();
            if (treeModel != null)
                treeModel.addTreeModelListener(this);
(Review ID: 116937)
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