6709913: BasicComboBoxUI.isPopupVisible returns NullPointerException

Reviewed-by: serb

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

@@ -905,17 +905,19 @@ public class BasicComboBoxUI extends ComboBoxUI {
      * Tells if the popup is visible or not.
      */
     public boolean isPopupVisible( JComboBox<?> c ) {
-        return popup.isVisible();
+        return popup != null && popup.isVisible();
     }
 
     /**
      * Hides the popup.
      */
     public void setPopupVisible( JComboBox<?> c, boolean v ) {
-        if ( v ) {
-            popup.show();
-        } else {
-            popup.hide();
+        if (popup != null) {
+            if (v) {
+                popup.show();
+            } else {
+                popup.hide();
+            }
         }
     }
 

test/jdk/javax/swing/plaf/basic/BasicComboBoxUI/BasicComboNPE.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2020, 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.
+ */
+
+/* @test
+   @bug 6709913
+   @summary Verifies BasicComboBoxUI.isPopupVisible does not return NPE
+   @run main BasicComboNPE
+ */
+import javax.swing.SwingUtilities;
+import javax.swing.JComboBox;
+import javax.swing.UIManager;
+import javax.swing.UnsupportedLookAndFeelException;
+import javax.swing.ComboBoxModel;
+import java.awt.IllegalComponentStateException;
+
+public class BasicComboNPE extends JComboBox
+{
+    public static void main(String[] args) {
+        for (UIManager.LookAndFeelInfo laf : UIManager.getInstalledLookAndFeels()) {
+            try {
+                System.out.println("Test for LookAndFeel " + laf.getClassName());
+                UIManager.setLookAndFeel(laf.getClassName());
+                new BasicComboNPE().getModel();
+            } catch (IllegalComponentStateException | ClassNotFoundException | InstantiationException |
+                     IllegalAccessException | UnsupportedLookAndFeelException e ) {
+               //System.out.println(e);
+            }
+        }
+
+    }
+
+    @Override
+    public ComboBoxModel getModel()
+    {
+        setPopupVisible(true);
+        isPopupVisible();
+        return super.getModel();
+    }
+}