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POcan't remove first element from jcombobox
 

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  1. POcan't remove first element from jcombobox
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    <p>I cannot remove the first element from jcombobox. my code is as follows,</p> <pre><code>JComboBox cBox= cBox= new JComboBox(); ... while (cBox.getItemCount() &gt; 0) cBox.removeItemAt(0); </code></pre> <p>For a test run, i had 3 items in the cBox. When it gets to removeItemAt(0), the debug goes haywire going in to some File access code which is absolutely not related. Does this twice then gets the below exception. I tried removeAllItems() which directly gets the same exception. However, removeItem(1) works as it should until theres only 1 element left. The exception doesn't crash the app and i can see no items in the combobox after so it worked a little. What exactly am i doing wrong.</p> <pre><code>Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at util.Gui$4.actionPerformed(Gui.java:111) at javax.swing.JComboBox.fireActionEvent(Unknown Source) at javax.swing.JComboBox.contentsChanged(Unknown Source) at javax.swing.AbstractListModel.fireContentsChanged(Unknown Source) at javax.swing.DefaultComboBoxModel.setSelectedItem(Unknown Source) at javax.swing.DefaultComboBoxModel.removeElementAt(Unknown Source) at javax.swing.JComboBox.removeItemAt(Unknown Source) at util.Gui.prepareSubLists(Gui.java:164) at util.Gui$3.actionPerformed(Gui.java:97) at javax.swing.JComboBox.fireActionEvent(Unknown Source) at javax.swing.JComboBox.setSelectedItem(Unknown Source) at javax.swing.JComboBox.setSelectedIndex(Unknown Source) at javax.swing.plaf.basic.BasicComboPopup$Handler.mouseReleased(Unknown Source) at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source) at java.awt.Component.processMouseEvent(Unknown Source) at javax.swing.JComponent.processMouseEvent(Unknown Source) at javax.swing.plaf.basic.BasicComboPopup$1.processMouseEvent(Unknown Source) at java.awt.Component.processEvent(Unknown Source) at java.awt.Container.processEvent(Unknown Source) at java.awt.Component.dispatchEventImpl(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Window.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source) </code></pre>
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    1. USJonas
    1. USmechanicum
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    1. COIt would be useful if you put your actual code here. It could be the while condition as mre says, or any other issues causing NPE somewhere!
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      1. USAshkan Aryan
    2. COthe problem is in the code you are not showing, see the first line of your stacktrace: `at util.Gui$4.actionPerformed(Gui.java:111)`
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      1. USkleopatra
    3. COi had to add a single blank item then delete the rest. It seems incapable of delet all items from the combobox items.
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      1. USmechanicum
 

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