--- a/src/share/classes/com/sun/java/swing/plaf/windows/WindowsRootPaneUI.java	Mon Apr 10 16:17:00 2017 +0530
+++ b/src/share/classes/com/sun/java/swing/plaf/windows/WindowsRootPaneUI.java	Tue Feb 07 19:54:46 2017 +0300
@@ -165,8 +165,11 @@
         }
 
         public boolean postProcessKeyEvent(KeyEvent ev) {
-            if(ev.isConsumed()) {
-                // do not manage consumed event
+            if(ev.isConsumed() && ev.getKeyCode() != KeyEvent.VK_ALT) {
+                // mnemonic combination, it's consumed, but we need
+                // set altKeyPressed to false, otherwise after selection
+                // component by mnemonic combination a menu will be open
+                altKeyPressed = false;
                 return false;
             }
             if (ev.getKeyCode() == KeyEvent.VK_ALT) {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/com/sun/java/swing/plaf/windows/Test8173145.java	Tue Feb 07 19:54:46 2017 +0300
@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2017, 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 8173145
+   @summary Menu is activated after using mnemonic Alt/Key combination
+   @modules java.desktop/com.sun.java.swing.plaf.windows
+   @run main Test8173145
+*/
+
+import java.awt.*;
+import java.awt.event.KeyEvent;
+import java.lang.reflect.InvocationTargetException;
+
+import javax.swing.*;
+
+public class Test8173145 {
+
+    private volatile static JButton btn;
+    private volatile static boolean uiCreated;
+
+    public static void main(String[] args) throws InvocationTargetException, InterruptedException, AWTException {
+        SwingUtilities.invokeAndWait(new Runnable() {
+            @Override
+            public void run() {
+                try {
+                    uiCreated = createGUI();
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+            }
+        });
+
+        if (uiCreated) {
+            test();
+        } else {
+            //no windows l&f, skip the test
+        }
+    }
+
+    private static void test() {
+        final Robot robot;
+        try {
+            robot = new Robot();
+        } catch (AWTException e) {
+            throw new RuntimeException(e);
+        }
+        robot.setAutoDelay(100);
+        robot.waitForIdle();
+
+        robot.keyPress(KeyEvent.VK_ALT);
+        robot.keyPress(KeyEvent.VK_M);
+        robot.keyRelease(KeyEvent.VK_M);
+        robot.keyRelease(KeyEvent.VK_ALT);
+
+        Component focusOwner = KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner();
+
+        if (focusOwner != btn) {
+            throw new RuntimeException("Wrong focus owner");
+        }
+    }
+
+    private static boolean createGUI() {
+        try {
+            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
+        } catch (Exception e) {
+            return false;
+        }
+        JFrame f = new JFrame();
+
+        JPanel panel = new JPanel();
+        btn = new JButton("Mmmmm");
+        btn.setMnemonic(KeyEvent.VK_M);
+        btn.setDisplayedMnemonicIndex(0);
+        panel.add(btn);
+
+        JTextField tf = new JTextField();
+        tf.setColumns(10);
+        panel.add(tf);
+
+        f.setJMenuBar(getMenuBar());
+        f.add(panel);
+        f.pack();
+        f.setVisible(true);
+        tf.requestFocus();
+        return true;
+    }
+
+    static JMenuBar getMenuBar() {
+        JMenuBar menuBar;
+        JMenu menu;
+
+        menuBar = new JMenuBar();
+
+        menu = new JMenu("Menu");
+        menuBar.add(menu);
+
+        JMenuItem mi = new JMenuItem("test");
+        menu.add(mi);
+
+        return menuBar;
+    }
+}