FULL PRODUCT VERSION :
jre7u3 - jre7u6

ADDITIONAL OS VERSION INFORMATION :
Windows7

A DESCRIPTION OF THE PROBLEM :
ClassCastException in rendering null value in JComboBox

REGRESSION. Last worked in version 6u31


ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
at info.fingo.asist.ComboBoxTest$IntComboRenderer.getListCellRendererComponent(ComboBoxTest.java:1)
at javax.swing.plaf.basic.BasicComboBoxUI.getBaseline(BasicComboBoxUI.java:979)
at javax.swing.plaf.metal.MetalComboBoxUI.getBaseline(MetalComboBoxUI.java:149)
at javax.swing.JComponent.getBaseline(JComponent.java:2560)
at javax.swing.GroupLayout$ComponentSpring.getBaseline(GroupLayout.java:3075)
at javax.swing.GroupLayout$BaselineGroup.calculateBaselineAndResizeBehavior(GroupLayout.java:2732)
at javax.swing.GroupLayout$BaselineGroup.calculateSize(GroupLayout.java:2708)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1622)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1624)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout.calculateAutopadding(GroupLayout.java:1071)
at javax.swing.GroupLayout.prepare(GroupLayout.java:1059)
at javax.swing.GroupLayout.preferredLayoutSize(GroupLayout.java:878)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1662)
at java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:719)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1662)
at javax.swing.JRootPane$RootLayout.preferredLayoutSize(JRootPane.java:917)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1662)
at java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:719)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at java.awt.Window.pack(Window.java:809)
at info.fingo.asist.ComboBoxTest.main(ComboBoxTest.java:66)
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
at info.fingo.asist.ComboBoxTest$IntComboRenderer.getListCellRendererComponent(ComboBoxTest.java:1)
at javax.swing.plaf.basic.BasicComboBoxUI.getBaseline(BasicComboBoxUI.java:979)
at javax.swing.plaf.metal.MetalComboBoxUI.getBaseline(MetalComboBoxUI.java:149)
at javax.swing.JComponent.getBaseline(JComponent.java:2560)
at javax.swing.GroupLayout$ComponentSpring.getBaseline(GroupLayout.java:3075)
at javax.swing.GroupLayout$BaselineGroup.calculateBaselineAndResizeBehavior(GroupLayout.java:2732)
at javax.swing.GroupLayout$BaselineGroup.calculateSize(GroupLayout.java:2708)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1622)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1624)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$SequentialGroup.setValidSize(GroupLayout.java:2017)
at javax.swing.GroupLayout$Group.setSize(GroupLayout.java:1587)
at javax.swing.GroupLayout.calculateAutopadding(GroupLayout.java:1079)
at javax.swing.GroupLayout.layoutContainer(GroupLayout.java:920)
at java.awt.Container.layout(Container.java:1503)
at java.awt.Container.doLayout(Container.java:1492)
at java.awt.Container.validateTree(Container.java:1688)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validate(Container.java:1623)
at java.awt.Window.dispatchEventImpl(Window.java:2717)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:713)
at java.awt.EventQueue.access$000(EventQueue.java:104)
at java.awt.EventQueue$3.run(EventQueue.java:672)
at java.awt.EventQueue$3.run(EventQueue.java:670)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:686)
at java.awt.EventQueue$4.run(EventQueue.java:684)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:683)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
at info.fingo.asist.ComboBoxTest$IntComboRenderer.getListCellRendererComponent(ComboBoxTest.java:1)
at javax.swing.plaf.basic.BasicComboBoxUI.getBaseline(BasicComboBoxUI.java:979)
at javax.swing.plaf.metal.MetalComboBoxUI.getBaseline(MetalComboBoxUI.java:149)
at javax.swing.JComponent.getBaseline(JComponent.java:2560)
at javax.swing.GroupLayout$ComponentSpring.getBaseline(GroupLayout.java:3075)
at javax.swing.GroupLayout$BaselineGroup.calculateBaselineAndResizeBehavior(GroupLayout.java:2732)
at javax.swing.GroupLayout$BaselineGroup.calculateSize(GroupLayout.java:2708)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1622)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1624)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$SequentialGroup.setValidSize(GroupLayout.java:2017)
at javax.swing.GroupLayout$Group.setSize(GroupLayout.java:1587)
at javax.swing.GroupLayout.calculateAutopadding(GroupLayout.java:1079)
at javax.swing.GroupLayout.layoutContainer(GroupLayout.java:920)
at java.awt.Container.layout(Container.java:1503)
at java.awt.Container.doLayout(Container.java:1492)
at java.awt.Container.validateTree(Container.java:1688)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validate(Container.java:1623)
at java.awt.Window.dispatchEventImpl(Window.java:2717)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:713)
at java.awt.EventQueue.access$000(EventQueue.java:104)
at java.awt.EventQueue$3.run(EventQueue.java:672)
at java.awt.EventQueue$3.run(EventQueue.java:670)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:686)
at java.awt.EventQueue$4.run(EventQueue.java:684)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:683)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------

/**
 * 30-08-2012
 */
package info.fingo.asist;


import java.awt.Component;
import java.io.Serializable;

import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.GroupLayout.ParallelGroup;
import javax.swing.JComboBox;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.ListCellRenderer;
import javax.swing.plaf.basic.BasicComboBoxRenderer;

public class ComboBoxTest
{
public static class IntComboRenderer implements ListCellRenderer<Integer>, Serializable
{

private static final long serialVersionUID = 1L;

protected final BasicComboBoxRenderer wrapped;

public IntComboRenderer()
{
super();
this.wrapped = new BasicComboBoxRenderer();
}

@Override
public Component getListCellRendererComponent( JList<? extends Integer> list, Integer value, int index,
boolean isSelected, boolean cellHasFocus )
{
this.wrapped.getListCellRendererComponent( list, value, index, isSelected, cellHasFocus );

if( value != null )
{
this.wrapped.setText( value.toString() );
}
else
{
this.wrapped.setText( "" );
}
return this.wrapped;
}

}

public static void main( String[] args )
{
JDialog dialog = new JDialog();
dialog.add( createPanel() );
dialog.setModal( true );
dialog.pack();
dialog.setVisible( true );
}

private static JPanel createPanel()
{
// does not work
Integer[] items = new Integer[] { null, 1, 2 };
// works fine
// Integer[] items = new Integer[] { 1, 2 };
JComboBox<Integer> nameTF = new JComboBox<>( items );

nameTF.setSelectedIndex( 0 );
nameTF.setRenderer( new IntComboRenderer() );

JPanel panel = new JPanel();

GroupLayout layout = new GroupLayout( panel );
panel.setLayout( layout );
layout.setAutoCreateContainerGaps( true );
layout.setAutoCreateGaps( true );

GroupLayout.SequentialGroup vGroup = layout.createSequentialGroup();
GroupLayout.SequentialGroup hGroup = layout.createSequentialGroup();
ParallelGroup labelsHG = layout.createParallelGroup();
ParallelGroup componentsHG = layout.createParallelGroup();

JLabel nameLabel = new JLabel( "mapping.instance.dialog_new.field_name" );
labelsHG.addComponent( nameLabel );
componentsHG.addComponent( nameTF );
vGroup.addGroup( layout.createParallelGroup( Alignment.BASELINE ).addComponent( nameLabel ).addComponent(
nameTF ) );

hGroup.addGroup( labelsHG );
hGroup.addGroup( componentsHG );
layout.setHorizontalGroup( hGroup );
layout.setVerticalGroup( vGroup );
return panel;
}

}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Change null handling in BasicComboBoxUI.getBaseline
line:

// if( value == null )
// {
// value = " ";
// }
// else if( value instanceof String && "".equals( value ) )
// {
// value = " ";
// }