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 * Copyright (c) 2000, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 *
 * 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).
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 * 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,
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 *
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package java.awt;

import java.awt.event.KeyEvent;
import sun.awt.AppContext;
import java.awt.event.InputEvent;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;
import java.io.Serializable;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.lang.reflect.Field;

An AWTKeyStroke represents a key action on the
keyboard, or equivalent input device. AWTKeyStrokes
can correspond to only a press or release of a
particular key, just as KEY_PRESSED and
KEY_RELEASED KeyEvents do;
alternately, they can correspond to typing a specific Java character, just
as KEY_TYPED KeyEvents do.
In all cases, AWTKeyStrokes can specify modifiers
(alt, shift, control, meta, altGraph, or a combination thereof) which must be present
during the action for an exact match.

AWTKeyStrokes are immutable, and are intended
to be unique. Client code should never create an
AWTKeyStroke on its own, but should instead use
a variant of getAWTKeyStroke. Client use of these factory
methods allows the AWTKeyStroke implementation
to cache and share instances efficiently.
Author:
Arnaud Weber, David Mendenhall
See Also:
getAWTKeyStroke
Since:
1.4/**
 * An <code>AWTKeyStroke</code> represents a key action on the
 * keyboard, or equivalent input device. <code>AWTKeyStroke</code>s
 * can correspond to only a press or release of a
 * particular key, just as <code>KEY_PRESSED</code> and
 * <code>KEY_RELEASED</code> <code>KeyEvent</code>s do;
 * alternately, they can correspond to typing a specific Java character, just
 * as <code>KEY_TYPED</code> <code>KeyEvent</code>s do.
 * In all cases, <code>AWTKeyStroke</code>s can specify modifiers
 * (alt, shift, control, meta, altGraph, or a combination thereof) which must be present
 * during the action for an exact match.
 * <p>
 * <code>AWTKeyStrokes</code> are immutable, and are intended
 * to be unique. Client code should never create an
 * <code>AWTKeyStroke</code> on its own, but should instead use
 * a variant of <code>getAWTKeyStroke</code>. Client use of these factory
 * methods allows the <code>AWTKeyStroke</code> implementation
 * to cache and share instances efficiently.
 *
 * @see #getAWTKeyStroke
 *
 * @author Arnaud Weber
 * @author David Mendenhall
 * @since 1.4
 */
public class AWTKeyStroke implements Serializable {
    static final long serialVersionUID = -6430539691155161871L;

    private static Map<String, Integer> modifierKeywords;
    
Associates VK_XXX (as a String) with code (as Integer). This is
done to avoid the overhead of the reflective call to find the
constant.
/**
     * Associates VK_XXX (as a String) with code (as Integer). This is
     * done to avoid the overhead of the reflective call to find the
     * constant.
     */
    private static VKCollection vks;

    //A key for the collection of AWTKeyStrokes within AppContext.
    private static Object APP_CONTEXT_CACHE_KEY = new Object();
    //A key withing the cache
    private static AWTKeyStroke APP_CONTEXT_KEYSTROKE_KEY = new AWTKeyStroke();

    /*
     * Reads keystroke class from AppContext and if null, puts there the
     * AWTKeyStroke class.
     * Must be called under locked AWTKeyStro
     */
    private static Class<AWTKeyStroke> getAWTKeyStrokeClass() {
        Class<AWTKeyStroke> clazz = (Class)AppContext.getAppContext().get(AWTKeyStroke.class);
        if (clazz == null) {
            clazz = AWTKeyStroke.class;
            AppContext.getAppContext().put(AWTKeyStroke.class, AWTKeyStroke.class);
        }
        return clazz;
    }

    private char keyChar = KeyEvent.CHAR_UNDEFINED;
    private int keyCode = KeyEvent.VK_UNDEFINED;
    private int modifiers;
    private boolean onKeyRelease;

    static {
        /* ensure that the necessary native libraries are loaded */
        Toolkit.loadLibraries();
    }

    
Constructs an AWTKeyStroke with default values.
The default values used are:

Property
Default Value

   
Key Char
   
KeyEvent.CHAR_UNDEFINED


   
Key Code
   
KeyEvent.VK_UNDEFINED


   
Modifiers
   
none


   
On key release?
   
false


AWTKeyStrokes should not be constructed
by client code. Use a variant of getAWTKeyStroke
instead.
See Also:
getAWTKeyStroke/**
     * Constructs an <code>AWTKeyStroke</code> with default values.
     * The default values used are:
     * <table border="1" summary="AWTKeyStroke default values">
     * <tr><th>Property</th><th>Default Value</th></tr>
     * <tr>
     *    <td>Key Char</td>
     *    <td><code>KeyEvent.CHAR_UNDEFINED</code></td>
     * </tr>
     * <tr>
     *    <td>Key Code</td>
     *    <td><code>KeyEvent.VK_UNDEFINED</code></td>
     * </tr>
     * <tr>
     *    <td>Modifiers</td>
     *    <td>none</td>
     * </tr>
     * <tr>
     *    <td>On key release?</td>
     *    <td><code>false</code></td>
     * </tr>
     * </table>
     *
     * <code>AWTKeyStroke</code>s should not be constructed
     * by client code. Use a variant of <code>getAWTKeyStroke</code>
     * instead.
     *
     * @see #getAWTKeyStroke
     */
    protected AWTKeyStroke() {
    }

    
Constructs an AWTKeyStroke with the specified
values. AWTKeyStrokes should not be constructed
by client code. Use a variant of getAWTKeyStroke
instead.
Params:
keyChar – the character value for a keyboard key
keyCode – the key code for this AWTKeyStroke
modifiers – a bitwise-ored combination of any modifiers
onKeyRelease – true if this
       AWTKeyStroke corresponds
       to a key release; false otherwise
See Also:
getAWTKeyStroke/**
     * Constructs an <code>AWTKeyStroke</code> with the specified
     * values. <code>AWTKeyStroke</code>s should not be constructed
     * by client code. Use a variant of <code>getAWTKeyStroke</code>
     * instead.
     *
     * @param keyChar the character value for a keyboard key
     * @param keyCode the key code for this <code>AWTKeyStroke</code>
     * @param modifiers a bitwise-ored combination of any modifiers
     * @param onKeyRelease <code>true</code> if this
     *        <code>AWTKeyStroke</code> corresponds
     *        to a key release; <code>false</code> otherwise
     * @see #getAWTKeyStroke
     */
    protected AWTKeyStroke(char keyChar, int keyCode, int modifiers,
                           boolean onKeyRelease) {
        this.keyChar = keyChar;
        this.keyCode = keyCode;
        this.modifiers = modifiers;
        this.onKeyRelease = onKeyRelease;
    }

    
Registers a new class which the factory methods in
AWTKeyStroke will use when generating new
instances of AWTKeyStrokes. After invoking this
method, the factory methods will return instances of the specified
Class. The specified Class must be either AWTKeyStroke
or derived from AWTKeyStroke, and it must have a
no-arg constructor. The constructor can be of any accessibility,
including private. This operation
flushes the current AWTKeyStroke cache.
Params:
subclass – the new Class of which the factory methods should create
       instances
Throws:
IllegalArgumentException – if subclass is null,
        or if subclass does not have a no-arg constructor
ClassCastException – if subclass is not
        AWTKeyStroke, or a class derived from
        AWTKeyStroke/**
     * Registers a new class which the factory methods in
     * <code>AWTKeyStroke</code> will use when generating new
     * instances of <code>AWTKeyStroke</code>s. After invoking this
     * method, the factory methods will return instances of the specified
     * Class. The specified Class must be either <code>AWTKeyStroke</code>
     * or derived from <code>AWTKeyStroke</code>, and it must have a
     * no-arg constructor. The constructor can be of any accessibility,
     * including <code>private</code>. This operation
     * flushes the current <code>AWTKeyStroke</code> cache.
     *
     * @param subclass the new Class of which the factory methods should create
     *        instances
     * @throws IllegalArgumentException if subclass is <code>null</code>,
     *         or if subclass does not have a no-arg constructor
     * @throws ClassCastException if subclass is not
     *         <code>AWTKeyStroke</code>, or a class derived from
     *         <code>AWTKeyStroke</code>
     */
    protected static void registerSubclass(Class<?> subclass) {
        if (subclass == null) {
            throw new IllegalArgumentException("subclass cannot be null");
        }
        synchronized (AWTKeyStroke.class) {
            Class<AWTKeyStroke> keyStrokeClass = (Class)AppContext.getAppContext().get(AWTKeyStroke.class);
            if (keyStrokeClass != null && keyStrokeClass.equals(subclass)){
                // Already registered
                return;
            }
        }
        if (!AWTKeyStroke.class.isAssignableFrom(subclass)) {
            throw new ClassCastException("subclass is not derived from AWTKeyStroke");
        }

        Constructor ctor = getCtor(subclass);

        String couldNotInstantiate = "subclass could not be instantiated";

        if (ctor == null) {
            throw new IllegalArgumentException(couldNotInstantiate);
        }
        try {
            AWTKeyStroke stroke = (AWTKeyStroke)ctor.newInstance((Object[]) null);
            if (stroke == null) {
                throw new IllegalArgumentException(couldNotInstantiate);
            }
        } catch (NoSuchMethodError e) {
            throw new IllegalArgumentException(couldNotInstantiate);
        } catch (ExceptionInInitializerError e) {
            throw new IllegalArgumentException(couldNotInstantiate);
        } catch (InstantiationException e) {
            throw new IllegalArgumentException(couldNotInstantiate);
        } catch (IllegalAccessException e) {
            throw new IllegalArgumentException(couldNotInstantiate);
        } catch (InvocationTargetException e) {
            throw new IllegalArgumentException(couldNotInstantiate);
        }

        synchronized (AWTKeyStroke.class) {
            AppContext.getAppContext().put(AWTKeyStroke.class, subclass);
            AppContext.getAppContext().remove(APP_CONTEXT_CACHE_KEY);
            AppContext.getAppContext().remove(APP_CONTEXT_KEYSTROKE_KEY);
        }
    }

    /* returns noarg Constructor for class with accessible flag. No security
       threat as accessible flag is set only for this Constructor object,
       not for Class constructor.
     */
    private static Constructor getCtor(final Class clazz)
    {
        Constructor ctor = AccessController.doPrivileged(new PrivilegedAction<Constructor>() {
            public Constructor run() {
                try {
                    Constructor ctor = clazz.getDeclaredConstructor((Class[]) null);
                    if (ctor != null) {
                        ctor.setAccessible(true);
                    }
                    return ctor;
                } catch (SecurityException e) {
                } catch (NoSuchMethodException e) {
                }
                return null;
            }
        });
        return (Constructor)ctor;
    }

    private static synchronized AWTKeyStroke getCachedStroke
        (char keyChar, int keyCode, int modifiers, boolean onKeyRelease)
    {
        Map<AWTKeyStroke, AWTKeyStroke> cache = (Map)AppContext.getAppContext().get(APP_CONTEXT_CACHE_KEY);
        AWTKeyStroke cacheKey = (AWTKeyStroke)AppContext.getAppContext().get(APP_CONTEXT_KEYSTROKE_KEY);

        if (cache == null) {
            cache = new HashMap<>();
            AppContext.getAppContext().put(APP_CONTEXT_CACHE_KEY, cache);
        }

        if (cacheKey == null) {
            try {
                Class<AWTKeyStroke> clazz = getAWTKeyStrokeClass();
                cacheKey = (AWTKeyStroke)getCtor(clazz).newInstance((Object[]) null);
                AppContext.getAppContext().put(APP_CONTEXT_KEYSTROKE_KEY, cacheKey);
            } catch (InstantiationException e) {
                assert(false);
            } catch (IllegalAccessException e) {
                assert(false);
            } catch (InvocationTargetException e) {
                assert(false);
            }
        }
        cacheKey.keyChar = keyChar;
        cacheKey.keyCode = keyCode;
        cacheKey.modifiers = mapNewModifiers(mapOldModifiers(modifiers));
        cacheKey.onKeyRelease = onKeyRelease;

        AWTKeyStroke stroke = (AWTKeyStroke)cache.get(cacheKey);
        if (stroke == null) {
            stroke = cacheKey;
            cache.put(stroke, stroke);
            AppContext.getAppContext().remove(APP_CONTEXT_KEYSTROKE_KEY);
        }
        return stroke;
    }

    
Returns a shared instance of an AWTKeyStroke
that represents a KEY_TYPED event for the
specified character.
Params:
keyChar – the character value for a keyboard key
Returns:
an AWTKeyStroke object for that key/**
     * Returns a shared instance of an <code>AWTKeyStroke</code>
     * that represents a <code>KEY_TYPED</code> event for the
     * specified character.
     *
     * @param keyChar the character value for a keyboard key
     * @return an <code>AWTKeyStroke</code> object for that key
     */
    public static AWTKeyStroke getAWTKeyStroke(char keyChar) {
        return getCachedStroke(keyChar, KeyEvent.VK_UNDEFINED, 0, false);
    }

    
Returns a shared instance of an AWTKeyStroke that represents a KEY_TYPED event for the specified Character object and a set of modifiers. Note that the first parameter is of type Character rather than char. This is to avoid inadvertent clashes with calls to getAWTKeyStroke(int keyCode, int modifiers).
The modifiers consist of any combination of following:

java.awt.event.InputEvent.SHIFT_DOWN_MASK
java.awt.event.InputEvent.CTRL_DOWN_MASK
java.awt.event.InputEvent.META_DOWN_MASK
java.awt.event.InputEvent.ALT_DOWN_MASK
java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK

The old modifiers listed below also can be used, but they are
mapped to _DOWN_ modifiers. 

java.awt.event.InputEvent.SHIFT_MASK
java.awt.event.InputEvent.CTRL_MASK
java.awt.event.InputEvent.META_MASK
java.awt.event.InputEvent.ALT_MASK
java.awt.event.InputEvent.ALT_GRAPH_MASK

also can be used, but they are mapped to _DOWN_ modifiers.
Since these numbers are all different powers of two, any combination of
them is an integer in which each bit represents a different modifier
key. Use 0 to specify no modifiers.
Params:
keyChar – the Character object for a keyboard character
modifiers – a bitwise-ored combination of any modifiers
Throws:
IllegalArgumentException – if keyChar is
      null
See Also:
InputEvent
Returns:
an AWTKeyStroke object for that key/**
     * Returns a shared instance of an {@code AWTKeyStroke}
     * that represents a {@code KEY_TYPED} event for the
     * specified Character object and a set of modifiers. Note
     * that the first parameter is of type Character rather than
     * char. This is to avoid inadvertent clashes with
     * calls to <code>getAWTKeyStroke(int keyCode, int modifiers)</code>.
     *
     * The modifiers consist of any combination of following:<ul>
     * <li>java.awt.event.InputEvent.SHIFT_DOWN_MASK
     * <li>java.awt.event.InputEvent.CTRL_DOWN_MASK
     * <li>java.awt.event.InputEvent.META_DOWN_MASK
     * <li>java.awt.event.InputEvent.ALT_DOWN_MASK
     * <li>java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK
     * </ul>
     * The old modifiers listed below also can be used, but they are
     * mapped to _DOWN_ modifiers. <ul>
     * <li>java.awt.event.InputEvent.SHIFT_MASK
     * <li>java.awt.event.InputEvent.CTRL_MASK
     * <li>java.awt.event.InputEvent.META_MASK
     * <li>java.awt.event.InputEvent.ALT_MASK
     * <li>java.awt.event.InputEvent.ALT_GRAPH_MASK
     * </ul>
     * also can be used, but they are mapped to _DOWN_ modifiers.
     *
     * Since these numbers are all different powers of two, any combination of
     * them is an integer in which each bit represents a different modifier
     * key. Use 0 to specify no modifiers.
     *
     * @param keyChar the Character object for a keyboard character
     * @param modifiers a bitwise-ored combination of any modifiers
     * @return an <code>AWTKeyStroke</code> object for that key
     * @throws IllegalArgumentException if <code>keyChar</code> is
     *       <code>null</code>
     *
     * @see java.awt.event.InputEvent
     */
    public static AWTKeyStroke getAWTKeyStroke(Character keyChar, int modifiers)
    {
        if (keyChar == null) {
            throw new IllegalArgumentException("keyChar cannot be null");
        }
        return getCachedStroke(keyChar.charValue(), KeyEvent.VK_UNDEFINED,
                               modifiers, false);
    }

    
Returns a shared instance of an AWTKeyStroke,
given a numeric key code and a set of modifiers, specifying
whether the key is activated when it is pressed or released.

The "virtual key" constants defined in
java.awt.event.KeyEvent can be
used to specify the key code. For example:

java.awt.event.KeyEvent.VK_ENTER
java.awt.event.KeyEvent.VK_TAB
java.awt.event.KeyEvent.VK_SPACE

Alternatively, the key code may be obtained by calling
java.awt.event.KeyEvent.getExtendedKeyCodeForChar.
The modifiers consist of any combination of:

java.awt.event.InputEvent.SHIFT_DOWN_MASK
java.awt.event.InputEvent.CTRL_DOWN_MASK
java.awt.event.InputEvent.META_DOWN_MASK
java.awt.event.InputEvent.ALT_DOWN_MASK
java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK

The old modifiers 

java.awt.event.InputEvent.SHIFT_MASK
java.awt.event.InputEvent.CTRL_MASK
java.awt.event.InputEvent.META_MASK
java.awt.event.InputEvent.ALT_MASK
java.awt.event.InputEvent.ALT_GRAPH_MASK

also can be used, but they are mapped to _DOWN_ modifiers.
Since these numbers are all different powers of two, any combination of
them is an integer in which each bit represents a different modifier
key. Use 0 to specify no modifiers.
Params:
keyCode – an int specifying the numeric code for a keyboard key
modifiers – a bitwise-ored combination of any modifiers
onKeyRelease – true if the AWTKeyStroke
       should represent a key release; false otherwise
See Also:
KeyEvent
InputEvent
Returns:
an AWTKeyStroke object for that key/**
     * Returns a shared instance of an <code>AWTKeyStroke</code>,
     * given a numeric key code and a set of modifiers, specifying
     * whether the key is activated when it is pressed or released.
     * <p>
     * The "virtual key" constants defined in
     * <code>java.awt.event.KeyEvent</code> can be
     * used to specify the key code. For example:<ul>
     * <li><code>java.awt.event.KeyEvent.VK_ENTER</code>
     * <li><code>java.awt.event.KeyEvent.VK_TAB</code>
     * <li><code>java.awt.event.KeyEvent.VK_SPACE</code>
     * </ul>
     * Alternatively, the key code may be obtained by calling
     * <code>java.awt.event.KeyEvent.getExtendedKeyCodeForChar</code>.
     *
     * The modifiers consist of any combination of:<ul>
     * <li>java.awt.event.InputEvent.SHIFT_DOWN_MASK
     * <li>java.awt.event.InputEvent.CTRL_DOWN_MASK
     * <li>java.awt.event.InputEvent.META_DOWN_MASK
     * <li>java.awt.event.InputEvent.ALT_DOWN_MASK
     * <li>java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK
     * </ul>
     * The old modifiers <ul>
     * <li>java.awt.event.InputEvent.SHIFT_MASK
     * <li>java.awt.event.InputEvent.CTRL_MASK
     * <li>java.awt.event.InputEvent.META_MASK
     * <li>java.awt.event.InputEvent.ALT_MASK
     * <li>java.awt.event.InputEvent.ALT_GRAPH_MASK
     * </ul>
     * also can be used, but they are mapped to _DOWN_ modifiers.
     *
     * Since these numbers are all different powers of two, any combination of
     * them is an integer in which each bit represents a different modifier
     * key. Use 0 to specify no modifiers.
     *
     * @param keyCode an int specifying the numeric code for a keyboard key
     * @param modifiers a bitwise-ored combination of any modifiers
     * @param onKeyRelease <code>true</code> if the <code>AWTKeyStroke</code>
     *        should represent a key release; <code>false</code> otherwise
     * @return an AWTKeyStroke object for that key
     *
     * @see java.awt.event.KeyEvent
     * @see java.awt.event.InputEvent
     */
    public static AWTKeyStroke getAWTKeyStroke(int keyCode, int modifiers,
                                               boolean onKeyRelease) {
        return getCachedStroke(KeyEvent.CHAR_UNDEFINED, keyCode, modifiers,
                               onKeyRelease);
    }

    
Returns a shared instance of an AWTKeyStroke,
given a numeric key code and a set of modifiers. The returned
AWTKeyStroke will correspond to a key press.

The "virtual key" constants defined in
java.awt.event.KeyEvent can be
used to specify the key code. For example:

java.awt.event.KeyEvent.VK_ENTER
java.awt.event.KeyEvent.VK_TAB
java.awt.event.KeyEvent.VK_SPACE

The modifiers consist of any combination of:

java.awt.event.InputEvent.SHIFT_DOWN_MASK
java.awt.event.InputEvent.CTRL_DOWN_MASK
java.awt.event.InputEvent.META_DOWN_MASK
java.awt.event.InputEvent.ALT_DOWN_MASK
java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK

The old modifiers 

java.awt.event.InputEvent.SHIFT_MASK
java.awt.event.InputEvent.CTRL_MASK
java.awt.event.InputEvent.META_MASK
java.awt.event.InputEvent.ALT_MASK
java.awt.event.InputEvent.ALT_GRAPH_MASK

also can be used, but they are mapped to _DOWN_ modifiers.
Since these numbers are all different powers of two, any combination of
them is an integer in which each bit represents a different modifier
key. Use 0 to specify no modifiers.
Params:
keyCode – an int specifying the numeric code for a keyboard key
modifiers – a bitwise-ored combination of any modifiers
See Also:
KeyEvent
InputEvent
Returns:
an AWTKeyStroke object for that key/**
     * Returns a shared instance of an <code>AWTKeyStroke</code>,
     * given a numeric key code and a set of modifiers. The returned
     * <code>AWTKeyStroke</code> will correspond to a key press.
     * <p>
     * The "virtual key" constants defined in
     * <code>java.awt.event.KeyEvent</code> can be
     * used to specify the key code. For example:<ul>
     * <li><code>java.awt.event.KeyEvent.VK_ENTER</code>
     * <li><code>java.awt.event.KeyEvent.VK_TAB</code>
     * <li><code>java.awt.event.KeyEvent.VK_SPACE</code>
     * </ul>
     * The modifiers consist of any combination of:<ul>
     * <li>java.awt.event.InputEvent.SHIFT_DOWN_MASK
     * <li>java.awt.event.InputEvent.CTRL_DOWN_MASK
     * <li>java.awt.event.InputEvent.META_DOWN_MASK
     * <li>java.awt.event.InputEvent.ALT_DOWN_MASK
     * <li>java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK
     * </ul>
     * The old modifiers <ul>
     * <li>java.awt.event.InputEvent.SHIFT_MASK
     * <li>java.awt.event.InputEvent.CTRL_MASK
     * <li>java.awt.event.InputEvent.META_MASK
     * <li>java.awt.event.InputEvent.ALT_MASK
     * <li>java.awt.event.InputEvent.ALT_GRAPH_MASK
     * </ul>
     * also can be used, but they are mapped to _DOWN_ modifiers.
     *
     * Since these numbers are all different powers of two, any combination of
     * them is an integer in which each bit represents a different modifier
     * key. Use 0 to specify no modifiers.
     *
     * @param keyCode an int specifying the numeric code for a keyboard key
     * @param modifiers a bitwise-ored combination of any modifiers
     * @return an <code>AWTKeyStroke</code> object for that key
     *
     * @see java.awt.event.KeyEvent
     * @see java.awt.event.InputEvent
     */
    public static AWTKeyStroke getAWTKeyStroke(int keyCode, int modifiers) {
        return getCachedStroke(KeyEvent.CHAR_UNDEFINED, keyCode, modifiers,
                               false);
    }

    
Returns an AWTKeyStroke which represents the
stroke which generated a given KeyEvent.

This method obtains the keyChar from a KeyTyped
event, and the keyCode from a KeyPressed or
KeyReleased event. The KeyEvent modifiers are
obtained for all three types of KeyEvent.
Params:
anEvent – the KeyEvent from which to
     obtain the AWTKeyStroke
Throws:
NullPointerException – if anEvent is null
Returns:
the AWTKeyStroke that precipitated the event/**
     * Returns an <code>AWTKeyStroke</code> which represents the
     * stroke which generated a given <code>KeyEvent</code>.
     * <p>
     * This method obtains the keyChar from a <code>KeyTyped</code>
     * event, and the keyCode from a <code>KeyPressed</code> or
     * <code>KeyReleased</code> event. The <code>KeyEvent</code> modifiers are
     * obtained for all three types of <code>KeyEvent</code>.
     *
     * @param anEvent the <code>KeyEvent</code> from which to
     *      obtain the <code>AWTKeyStroke</code>
     * @throws NullPointerException if <code>anEvent</code> is null
     * @return the <code>AWTKeyStroke</code> that precipitated the event
     */
    public static AWTKeyStroke getAWTKeyStrokeForEvent(KeyEvent anEvent) {
        int id = anEvent.getID();
        switch(id) {
          case KeyEvent.KEY_PRESSED:
          case KeyEvent.KEY_RELEASED:
            return getCachedStroke(KeyEvent.CHAR_UNDEFINED,
                                   anEvent.getKeyCode(),
                                   anEvent.getModifiers(),
                                   (id == KeyEvent.KEY_RELEASED));
          case KeyEvent.KEY_TYPED:
            return getCachedStroke(anEvent.getKeyChar(),
                                   KeyEvent.VK_UNDEFINED,
                                   anEvent.getModifiers(),
                                   false);
          default:
            // Invalid ID for this KeyEvent
            return null;
        }
    }

    
Parses a string and returns an AWTKeyStroke.
The string must have the following syntax:
   <modifiers>* (<typedID> | <pressedReleasedID>)
   modifiers := shift | control | ctrl | meta | alt | altGraph
   typedID := typed <typedKey>
   typedKey := string of length 1 giving Unicode character.
   pressedReleasedID := (pressed | released) key
   key := KeyEvent key code name, i.e. the name following "VK_".

If typed, pressed or released is not specified, pressed is assumed. Here
are some examples:
    "INSERT" => getAWTKeyStroke(KeyEvent.VK_INSERT, 0);
    "control DELETE" => getAWTKeyStroke(KeyEvent.VK_DELETE, InputEvent.CTRL_MASK);
    "alt shift X" => getAWTKeyStroke(KeyEvent.VK_X, InputEvent.ALT_MASK | InputEvent.SHIFT_MASK);
    "alt shift released X" => getAWTKeyStroke(KeyEvent.VK_X, InputEvent.ALT_MASK | InputEvent.SHIFT_MASK, true);
    "typed a" => getAWTKeyStroke('a');

Params:
s – a String formatted as described above
Throws:
IllegalArgumentException – if s is null,
       or is formatted incorrectly
Returns:
an AWTKeyStroke object for that String/**
     * Parses a string and returns an <code>AWTKeyStroke</code>.
     * The string must have the following syntax:
     * <pre>
     *    &lt;modifiers&gt;* (&lt;typedID&gt; | &lt;pressedReleasedID&gt;)
     *
     *    modifiers := shift | control | ctrl | meta | alt | altGraph
     *    typedID := typed &lt;typedKey&gt;
     *    typedKey := string of length 1 giving Unicode character.
     *    pressedReleasedID := (pressed | released) key
     *    key := KeyEvent key code name, i.e. the name following "VK_".
     * </pre>
     * If typed, pressed or released is not specified, pressed is assumed. Here
     * are some examples:
     * <pre>
     *     "INSERT" =&gt; getAWTKeyStroke(KeyEvent.VK_INSERT, 0);
     *     "control DELETE" =&gt; getAWTKeyStroke(KeyEvent.VK_DELETE, InputEvent.CTRL_MASK);
     *     "alt shift X" =&gt; getAWTKeyStroke(KeyEvent.VK_X, InputEvent.ALT_MASK | InputEvent.SHIFT_MASK);
     *     "alt shift released X" =&gt; getAWTKeyStroke(KeyEvent.VK_X, InputEvent.ALT_MASK | InputEvent.SHIFT_MASK, true);
     *     "typed a" =&gt; getAWTKeyStroke('a');
     * </pre>
     *
     * @param s a String formatted as described above
     * @return an <code>AWTKeyStroke</code> object for that String
     * @throws IllegalArgumentException if <code>s</code> is <code>null</code>,
     *        or is formatted incorrectly
     */
    public static AWTKeyStroke getAWTKeyStroke(String s) {
        if (s == null) {
            throw new IllegalArgumentException("String cannot be null");
        }

        final String errmsg = "String formatted incorrectly";

        StringTokenizer st = new StringTokenizer(s, " ");

        int mask = 0;
        boolean released = false;
        boolean typed = false;
        boolean pressed = false;

        synchronized (AWTKeyStroke.class) {
            if (modifierKeywords == null) {
                Map<String, Integer> uninitializedMap = new HashMap<>(8, 1.0f);
                uninitializedMap.put("shift",
                                     Integer.valueOf(InputEvent.SHIFT_DOWN_MASK
                                                     |InputEvent.SHIFT_MASK));
                uninitializedMap.put("control",
                                     Integer.valueOf(InputEvent.CTRL_DOWN_MASK
                                                     |InputEvent.CTRL_MASK));
                uninitializedMap.put("ctrl",
                                     Integer.valueOf(InputEvent.CTRL_DOWN_MASK
                                                     |InputEvent.CTRL_MASK));
                uninitializedMap.put("meta",
                                     Integer.valueOf(InputEvent.META_DOWN_MASK
                                                     |InputEvent.META_MASK));
                uninitializedMap.put("alt",
                                     Integer.valueOf(InputEvent.ALT_DOWN_MASK
                                                     |InputEvent.ALT_MASK));
                uninitializedMap.put("altGraph",
                                     Integer.valueOf(InputEvent.ALT_GRAPH_DOWN_MASK
                                                     |InputEvent.ALT_GRAPH_MASK));
                uninitializedMap.put("button1",
                                     Integer.valueOf(InputEvent.BUTTON1_DOWN_MASK));
                uninitializedMap.put("button2",
                                     Integer.valueOf(InputEvent.BUTTON2_DOWN_MASK));
                uninitializedMap.put("button3",
                                     Integer.valueOf(InputEvent.BUTTON3_DOWN_MASK));
                modifierKeywords =
                    Collections.synchronizedMap(uninitializedMap);
            }
        }

        int count = st.countTokens();

        for (int i = 1; i <= count; i++) {
            String token = st.nextToken();

            if (typed) {
                if (token.length() != 1 || i != count) {
                    throw new IllegalArgumentException(errmsg);
                }
                return getCachedStroke(token.charAt(0), KeyEvent.VK_UNDEFINED,
                                       mask, false);
            }

            if (pressed || released || i == count) {
                if (i != count) {
                    throw new IllegalArgumentException(errmsg);
                }

                String keyCodeName = "VK_" + token;
                int keyCode = getVKValue(keyCodeName);

                return getCachedStroke(KeyEvent.CHAR_UNDEFINED, keyCode,
                                       mask, released);
            }

            if (token.equals("released")) {
                released = true;
                continue;
            }
            if (token.equals("pressed")) {
                pressed = true;
                continue;
            }
            if (token.equals("typed")) {
                typed = true;
                continue;
            }

            Integer tokenMask = (Integer)modifierKeywords.get(token);
            if (tokenMask != null) {
                mask |= tokenMask.intValue();
            } else {
                throw new IllegalArgumentException(errmsg);
            }
        }

        throw new IllegalArgumentException(errmsg);
    }

    private static VKCollection getVKCollection() {
        if (vks == null) {
            vks = new VKCollection();
        }
        return vks;
    }
    
Returns the integer constant for the KeyEvent.VK field named
key. This will throw an
IllegalArgumentException if key is
not a valid constant.
/**
     * Returns the integer constant for the KeyEvent.VK field named
     * <code>key</code>. This will throw an
     * <code>IllegalArgumentException</code> if <code>key</code> is
     * not a valid constant.
     */
    private static int getVKValue(String key) {
        VKCollection vkCollect = getVKCollection();

        Integer value = vkCollect.findCode(key);

        if (value == null) {
            int keyCode = 0;
            final String errmsg = "String formatted incorrectly";

            try {
                keyCode = KeyEvent.class.getField(key).getInt(KeyEvent.class);
            } catch (NoSuchFieldException nsfe) {
                throw new IllegalArgumentException(errmsg);
            } catch (IllegalAccessException iae) {
                throw new IllegalArgumentException(errmsg);
            }
            value = Integer.valueOf(keyCode);
            vkCollect.put(key, value);
        }
        return value.intValue();
    }

    
Returns the character for this AWTKeyStroke.
See Also:
getAWTKeyStroke(char)
KeyEvent.getKeyChar
Returns:
a char value/**
     * Returns the character for this <code>AWTKeyStroke</code>.
     *
     * @return a char value
     * @see #getAWTKeyStroke(char)
     * @see KeyEvent#getKeyChar
     */
    public final char getKeyChar() {
        return keyChar;
    }

    
Returns the numeric key code for this AWTKeyStroke.
See Also:
getAWTKeyStroke(int, int)
KeyEvent.getKeyCode
Returns:
an int containing the key code value/**
     * Returns the numeric key code for this <code>AWTKeyStroke</code>.
     *
     * @return an int containing the key code value
     * @see #getAWTKeyStroke(int,int)
     * @see KeyEvent#getKeyCode
     */
    public final int getKeyCode() {
        return keyCode;
    }

    
Returns the modifier keys for this AWTKeyStroke.
See Also:
getAWTKeyStroke(int, int)
Returns:
an int containing the modifiers/**
     * Returns the modifier keys for this <code>AWTKeyStroke</code>.
     *
     * @return an int containing the modifiers
     * @see #getAWTKeyStroke(int,int)
     */
    public final int getModifiers() {
        return modifiers;
    }

    
Returns whether this AWTKeyStroke represents a key release.
See Also:
getAWTKeyStroke(int, int, boolean)
Returns:
true if this AWTKeyStroke
         represents a key release; false otherwise/**
     * Returns whether this <code>AWTKeyStroke</code> represents a key release.
     *
     * @return <code>true</code> if this <code>AWTKeyStroke</code>
     *          represents a key release; <code>false</code> otherwise
     * @see #getAWTKeyStroke(int,int,boolean)
     */
    public final boolean isOnKeyRelease() {
        return onKeyRelease;
    }

    
Returns the type of KeyEvent which corresponds to
this AWTKeyStroke.
See Also:
KeyEvent
Returns:
KeyEvent.KEY_PRESSED,
        KeyEvent.KEY_TYPED,
        or KeyEvent.KEY_RELEASED/**
     * Returns the type of <code>KeyEvent</code> which corresponds to
     * this <code>AWTKeyStroke</code>.
     *
     * @return <code>KeyEvent.KEY_PRESSED</code>,
     *         <code>KeyEvent.KEY_TYPED</code>,
     *         or <code>KeyEvent.KEY_RELEASED</code>
     * @see java.awt.event.KeyEvent
     */
    public final int getKeyEventType() {
        if (keyCode == KeyEvent.VK_UNDEFINED) {
            return KeyEvent.KEY_TYPED;
        } else {
            return (onKeyRelease)
                ? KeyEvent.KEY_RELEASED
                : KeyEvent.KEY_PRESSED;
        }
    }

    
Returns a numeric value for this object that is likely to be unique,
making it a good choice as the index value in a hash table.
Returns:
an int that represents this object/**
     * Returns a numeric value for this object that is likely to be unique,
     * making it a good choice as the index value in a hash table.
     *
     * @return an int that represents this object
     */
    public int hashCode() {
        return (((int)keyChar) + 1) * (2 * (keyCode + 1)) * (modifiers + 1) +
            (onKeyRelease ? 1 : 2);
    }

    
Returns true if this object is identical to the specified object.
Params:
anObject – the Object to compare this object to
Returns:
true if the objects are identical/**
     * Returns true if this object is identical to the specified object.
     *
     * @param anObject the Object to compare this object to
     * @return true if the objects are identical
     */
    public final boolean equals(Object anObject) {
        if (anObject instanceof AWTKeyStroke) {
            AWTKeyStroke ks = (AWTKeyStroke)anObject;
            return (ks.keyChar == keyChar && ks.keyCode == keyCode &&
                    ks.onKeyRelease == onKeyRelease &&
                    ks.modifiers == modifiers);
        }
        return false;
    }

    
Returns a string that displays and identifies this object's properties.
The String returned by this method can be passed
as a parameter to getAWTKeyStroke(String) to produce
a key stroke equal to this key stroke.
See Also:
getAWTKeyStroke(String)
Returns:
a String representation of this object/**
     * Returns a string that displays and identifies this object's properties.
     * The <code>String</code> returned by this method can be passed
     * as a parameter to <code>getAWTKeyStroke(String)</code> to produce
     * a key stroke equal to this key stroke.
     *
     * @return a String representation of this object
     * @see #getAWTKeyStroke(String)
     */
    public String toString() {
        if (keyCode == KeyEvent.VK_UNDEFINED) {
            return getModifiersText(modifiers) + "typed " + keyChar;
        } else {
            return getModifiersText(modifiers) +
                (onKeyRelease ? "released" : "pressed") + " " +
                getVKText(keyCode);
        }
    }

    static String getModifiersText(int modifiers) {
        StringBuilder buf = new StringBuilder();

        if ((modifiers & InputEvent.SHIFT_DOWN_MASK) != 0 ) {
            buf.append("shift ");
        }
        if ((modifiers & InputEvent.CTRL_DOWN_MASK) != 0 ) {
            buf.append("ctrl ");
        }
        if ((modifiers & InputEvent.META_DOWN_MASK) != 0 ) {
            buf.append("meta ");
        }
        if ((modifiers & InputEvent.ALT_DOWN_MASK) != 0 ) {
            buf.append("alt ");
        }
        if ((modifiers & InputEvent.ALT_GRAPH_DOWN_MASK) != 0 ) {
            buf.append("altGraph ");
        }
        if ((modifiers & InputEvent.BUTTON1_DOWN_MASK) != 0 ) {
            buf.append("button1 ");
        }
        if ((modifiers & InputEvent.BUTTON2_DOWN_MASK) != 0 ) {
            buf.append("button2 ");
        }
        if ((modifiers & InputEvent.BUTTON3_DOWN_MASK) != 0 ) {
            buf.append("button3 ");
        }

        return buf.toString();
    }

    static String getVKText(int keyCode) {
        VKCollection vkCollect = getVKCollection();
        Integer key = Integer.valueOf(keyCode);
        String name = vkCollect.findName(key);
        if (name != null) {
            return name.substring(3);
        }
        int expected_modifiers =
            (Modifier.PUBLIC | Modifier.STATIC | Modifier.FINAL);

        Field[] fields = KeyEvent.class.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            try {
                if (fields[i].getModifiers() == expected_modifiers
                    && fields[i].getType() == Integer.TYPE
                    && fields[i].getName().startsWith("VK_")
                    && fields[i].getInt(KeyEvent.class) == keyCode)
                {
                    name = fields[i].getName();
                    vkCollect.put(name, key);
                    return name.substring(3);
                }
            } catch (IllegalAccessException e) {
                assert(false);
            }
        }
        return "UNKNOWN";
    }

    
Returns a cached instance of AWTKeyStroke (or a subclass of
AWTKeyStroke) which is equal to this instance.
Returns:
a cached instance which is equal to this instance/**
     * Returns a cached instance of <code>AWTKeyStroke</code> (or a subclass of
     * <code>AWTKeyStroke</code>) which is equal to this instance.
     *
     * @return a cached instance which is equal to this instance
     */
    protected Object readResolve() throws java.io.ObjectStreamException {
        synchronized (AWTKeyStroke.class) {
            if (getClass().equals(getAWTKeyStrokeClass())) {
                return  getCachedStroke(keyChar, keyCode, modifiers, onKeyRelease);
            }
        }
        return this;
    }

    private static int mapOldModifiers(int modifiers) {
        if ((modifiers & InputEvent.SHIFT_MASK) != 0) {
            modifiers |= InputEvent.SHIFT_DOWN_MASK;
        }
        if ((modifiers & InputEvent.ALT_MASK) != 0) {
            modifiers |= InputEvent.ALT_DOWN_MASK;
        }
        if ((modifiers & InputEvent.ALT_GRAPH_MASK) != 0) {
            modifiers |= InputEvent.ALT_GRAPH_DOWN_MASK;
        }
        if ((modifiers & InputEvent.CTRL_MASK) != 0) {
            modifiers |= InputEvent.CTRL_DOWN_MASK;
        }
        if ((modifiers & InputEvent.META_MASK) != 0) {
            modifiers |= InputEvent.META_DOWN_MASK;
        }

        modifiers &= InputEvent.SHIFT_DOWN_MASK
            | InputEvent.ALT_DOWN_MASK
            | InputEvent.ALT_GRAPH_DOWN_MASK
            | InputEvent.CTRL_DOWN_MASK
            | InputEvent.META_DOWN_MASK
            | InputEvent.BUTTON1_DOWN_MASK
            | InputEvent.BUTTON2_DOWN_MASK
            | InputEvent.BUTTON3_DOWN_MASK;

        return modifiers;
    }

    private static int mapNewModifiers(int modifiers) {
        if ((modifiers & InputEvent.SHIFT_DOWN_MASK) != 0) {
            modifiers |= InputEvent.SHIFT_MASK;
        }
        if ((modifiers & InputEvent.ALT_DOWN_MASK) != 0) {
            modifiers |= InputEvent.ALT_MASK;
        }
        if ((modifiers & InputEvent.ALT_GRAPH_DOWN_MASK) != 0) {
            modifiers |= InputEvent.ALT_GRAPH_MASK;
        }
        if ((modifiers & InputEvent.CTRL_DOWN_MASK) != 0) {
            modifiers |= InputEvent.CTRL_MASK;
        }
        if ((modifiers & InputEvent.META_DOWN_MASK) != 0) {
            modifiers |= InputEvent.META_MASK;
        }

        return modifiers;
    }

}

class VKCollection {
    Map<Integer, String> code2name;
    Map<String, Integer> name2code;

    public VKCollection() {
        code2name = new HashMap<>();
        name2code = new HashMap<>();
    }

    public synchronized void put(String name, Integer code) {
        assert((name != null) && (code != null));
        assert(findName(code) == null);
        assert(findCode(name) == null);
        code2name.put(code, name);
        name2code.put(name, code);
    }

    public synchronized Integer findCode(String name) {
        assert(name != null);
        return (Integer)name2code.get(name);
    }

    public synchronized String findName(Integer code) {
        assert(code != null);
        return (String)code2name.get(code);
    }
}