Runtime exception when continuously updating a JList

Question

Hello,
my program has a JList to display some information and updates the content of this JList while the program is running. The JList is put in a JScrollPane and uses DefaultListModel to store its elements(the elements are all String objects).
Initially the JList is empty. After the program starts, new elements will be continuously added into DefaultListModel with the addElement(Object obj) method. Once there are 50 elements in the JList, the program removes the first element (index=0) before adding a new element to the JList.
The program seems to work fine, except it randomly generates ArrayIndexOutOfBoundsException at runtime, which is really annoying. Can someone help me to solve this problem? Many thanks.
Part of the program is listed below:
DefaultListModel tupleListModel=new DefaultListModel();
JList tupleList=new JList(tupleListModel);
JScrollPane sp1=new JScrollPane(tupleList);
for(int i=0;i<50;i++)
        tupleListModel.addElement(op.nextTuple().toString());
while(true){
         tupleListModel.remove(0);
         tupleListModel.addElement(op.nextTuple().toString());
}One of the runtime error message is:
java.lang.ArrayIndexOutOfBoundsException: 49 >= 49
at java.util.Vector.elementAt(Vector.java:431)
at javax.swing.DefaultListModel.getElementAt(DefaultListModel.java:70)
at javax.swing.plaf.basic.BasicListUI.updateLayoutState(BasicListUI.java:1147)
at javax.swing.plaf.basic.BasicListUI.maybeUpdateLayoutState(BasicListUI.java:1098)
at javax.swing.plaf.basic.BasicListUI.getPreferredSize(BasicListUI.java:281)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1275)
at javax.swing.ScrollPaneLayout.layoutContainer(ScrollPaneLayout.java:769)
at java.awt.Container.layout(Container.java:1020)
at java.awt.Container.doLayout(Container.java:1010)
at java.awt.Container.validateTree(Container.java:1092)
at java.awt.Container.validate(Container.java:1067)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:353)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:116)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
The other one is:
java.lang.ArrayIndexOutOfBoundsException: 49
at javax.swing.plaf.basic.BasicListUI.updateLayoutState(BasicListUI.java:1155)
at javax.swing.plaf.basic.BasicListUI.maybeUpdateLayoutState(BasicListUI.java:1098)
at javax.swing.plaf.basic.BasicListUI.getPreferredSize(BasicListUI.java:281)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1275)
at javax.swing.JList.getScrollableTracksViewportWidth(JList.java:2147)
at javax.swing.ScrollPaneLayout.layoutContainer(ScrollPaneLayout.java:786)
at java.awt.Container.layout(Container.java:1020)
at java.awt.Container.doLayout(Container.java:1010)
at java.awt.Container.validateTree(Container.java:1092)
at java.awt.Container.validate(Container.java:1067)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:353)

Answer 1

It's removing an item in the middle of trying to figure out what the preferred size of the jlist is. I would be that BasicListUI.updateLayoutState() has code in it something like thisint numItems = model.getSize();
for (int i=0; i<numItems; i++) {
String text = model..getElementAt(i).toString();  // bad time for the size to change
}If the size changes, the loop will still iterate to what used to be the size. Try using SwingUtilities.invokeLater() when to update the list so that the changes will happen on the event thread.