7195179: ClassCastException for null values in JComboBox

Reviewed-by: alexsch

src/share/classes/javax/swing/plaf/basic/BasicComboBoxUI.java

@@ -971,14 +971,16 @@ public class BasicComboBoxUI extends ComboBoxUI {
                     // cells, if not, this needs to loop through all.
                     value = comboBox.getModel().getElementAt(0);
                 }
-                if (value == null) {
-                    value = " ";
-                } else if (value instanceof String && "".equals(value)) {
-                    value = " ";
-                }
                 Component component = renderer.
                         getListCellRendererComponent(listBox, value, -1,
                                                      false, false);
+                if (component instanceof JLabel) {
+                    JLabel label = (JLabel) component;
+                    String text = label.getText();
+                    if ((text == null) || text.isEmpty()) {
+                        label.setText(" ");
+                    }
+                }
                 if (component instanceof JComponent) {
                     component.setFont(comboBox.getFont());
                 }

test/javax/swing/JComboBox/7195179/Test7195179.java

+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.awt.Component;
+import javax.swing.GroupLayout;
+import javax.swing.JComboBox;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.JList;
+import javax.swing.JPanel;
+import javax.swing.ListCellRenderer;
+import javax.swing.plaf.basic.BasicComboBoxRenderer;
+
+import static javax.swing.SwingUtilities.invokeAndWait;
+
+/*
+ * @test
+ * @bug 7195179
+ * @summary Tests that combobox works with generified renderers
+ * @author Sergey Malenkov
+ */
+
+public class Test7195179 {
+    public static void main(String[] args) throws Exception {
+        invokeAndWait(new Runnable() {
+            @Override
+            public void run() {
+                Integer[] items = {null, 1, 2, 3};
+                JComboBox<Integer> combo = new JComboBox<>(items);
+                JLabel label = new JLabel("choose:");
+                JPanel panel = new JPanel();
+                GroupLayout layout = new GroupLayout(panel);
+                panel.setLayout(layout);
+                label.setLabelFor(combo);
+                combo.setSelectedIndex(0);
+                combo.setRenderer(new ListCellRenderer<Integer>() {
+                    private final BasicComboBoxRenderer renderer = new BasicComboBoxRenderer();
+
+                    @Override
+                    public Component getListCellRendererComponent(JList<? extends Integer> list, Integer value, int index, boolean isSelected, boolean cellHasFocus) {
+                        return this.renderer.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
+                    }
+                });
+                layout.setAutoCreateContainerGaps(true);
+                layout.setAutoCreateGaps(true);
+                layout.setHorizontalGroup(layout.createSequentialGroup()
+                        .addGroup(layout.createParallelGroup().addComponent(label))
+                        .addGroup(layout.createParallelGroup().addComponent(combo)));
+                layout.setVerticalGroup(layout
+                        .createSequentialGroup()
+                        .addGroup(layout
+                                .createParallelGroup(GroupLayout.Alignment.BASELINE)
+                                .addComponent(label)
+                                .addComponent(combo)));
+
+                JFrame frame = new JFrame(getClass().getSimpleName());
+                frame.add(panel);
+                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
+                frame.pack();
+                frame.setVisible(true);
+            }
+        });
+    }
+}