src/java.desktop/share/classes/java/awt/AWTKeyStroke.java

/*
 * Copyright (c) 2000, 2025, 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
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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
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package java.awt;

import java.awt.event.InputEvent;
import java.awt.event.KeyEvent;
import java.io.Serial;
import java.io.Serializable;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;

import sun.awt.AppContext;
import sun.swing.SwingAccessor;

/**
 * An {@code AWTKeyStroke} represents a key action on the
 * keyboard, or equivalent input device. {@code AWTKeyStroke}s
 * can correspond to only a press or release of a
 * particular key, just as {@code KEY_PRESSED} and
 * {@code KEY_RELEASED KeyEvent}s do;
 * alternately, they can correspond to typing a specific Java character, just
 * as {@code KEY_TYPED KeyEvent}s do.
 * In all cases, {@code AWTKeyStroke}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} are immutable, and are intended
 * to be unique. Client code should never create an
 * {@code AWTKeyStroke} on its own, but should instead use
 * a variant of {@code getAWTKeyStroke}. Client use of these factory
 * methods allows the {@code AWTKeyStroke} implementation
 * to cache and share instances efficiently.
 *
 * @see #getAWTKeyStroke
 *
 * @author Arnaud Weber
 * @author David Mendenhall
 * @since 1.4
 */
public class AWTKeyStroke implements Serializable {

    /**
     * Use serialVersionUID from JDK 1.4 for interoperability.
     */
    @Serial
    private 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.
     */
    private static VKCollection vks;

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

    /**
     * @serial The character value for a keyboard key.
     */
    private char keyChar = KeyEvent.CHAR_UNDEFINED;

    /**
     * @serial The key code for this {@code AWTKeyStroke}.
     */
    private int keyCode = KeyEvent.VK_UNDEFINED;

    /**
     * @serial The bitwise-ored combination of any modifiers.
     */
    private int modifiers;

    /**
     * @serial {@code true} if this {@code AWTKeyStroke} corresponds to a key release;
     * {@code false} otherwise.
     */
    private boolean onKeyRelease;

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

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

    /**
     * Constructs an {@code AWTKeyStroke} with the specified
     * values. {@code AWTKeyStroke}s should not be constructed
     * by client code. Use a variant of {@code getAWTKeyStroke}
     * instead.
     *
     * @param keyChar the character value for a keyboard key
     * @param keyCode the key code for this {@code AWTKeyStroke}
     * @param modifiers a bitwise-ored combination of any modifiers
     * @param onKeyRelease {@code true} if this
     *        {@code AWTKeyStroke} corresponds
     *        to a key release; {@code false} 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;
    }

    /**
     * The method has no effect and is only left present to avoid introducing
     * a binary incompatibility.
     *
     * @param subclass the new Class of which the factory methods should create
     *        instances
     * @deprecated
     */
    @Deprecated
    protected static void registerSubclass(Class<?> subclass) {
    }

    private static synchronized AWTKeyStroke getCachedStroke
        (char keyChar, int keyCode, int modifiers, boolean onKeyRelease)
    {
        @SuppressWarnings("unchecked")
        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) {
            cacheKey = SwingAccessor.getKeyStrokeAccessor().create();
            AppContext.getAppContext().put(APP_CONTEXT_KEYSTROKE_KEY, cacheKey);
        }

        cacheKey.keyChar = keyChar;
        cacheKey.keyCode = keyCode;
        cacheKey.modifiers = mapNewModifiers(mapOldModifiers(modifiers));
        cacheKey.onKeyRelease = onKeyRelease;

        AWTKeyStroke stroke = 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 {@code AWTKeyStroke}
     * that represents a {@code KEY_TYPED} event for the
     * specified character.
     *
     * @param keyChar the character value for a keyboard key
     * @return an {@code AWTKeyStroke} object for that key
     */
    public static AWTKeyStroke getAWTKeyStroke(char keyChar) {
        return getCachedStroke(keyChar, KeyEvent.VK_UNDEFINED, 0, false);
    }

    /**
     * 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)}.
     *
     * 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} object for that key
     * @throws IllegalArgumentException if {@code keyChar} is
     *       {@code null}
     *
     * @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 {@code AWTKeyStroke},
     * 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} can be
     * used to specify the key code. For example:<ul>
     * <li>{@code java.awt.event.KeyEvent.VK_ENTER}
     * <li>{@code java.awt.event.KeyEvent.VK_TAB}
     * <li>{@code java.awt.event.KeyEvent.VK_SPACE}
     * </ul>
     * Alternatively, the key code may be obtained by calling
     * {@code java.awt.event.KeyEvent.getExtendedKeyCodeForChar}.
     *
     * 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} if the {@code AWTKeyStroke}
     *        should represent a key release; {@code false} 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 {@code AWTKeyStroke},
     * given a numeric key code and a set of modifiers. The returned
     * {@code AWTKeyStroke} will correspond to a key press.
     * <p>
     * The "virtual key" constants defined in
     * {@code java.awt.event.KeyEvent} can be
     * used to specify the key code. For example:<ul>
     * <li>{@code java.awt.event.KeyEvent.VK_ENTER}
     * <li>{@code java.awt.event.KeyEvent.VK_TAB}
     * <li>{@code java.awt.event.KeyEvent.VK_SPACE}
     * </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} 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 {@code AWTKeyStroke} which represents the
     * stroke which generated a given {@code KeyEvent}.
     * <p>
     * This method obtains the keyChar from a {@code KeyTyped}
     * event, and the keyCode from a {@code KeyPressed} or
     * {@code KeyReleased} event. The {@code KeyEvent} modifiers are
     * obtained for all three types of {@code KeyEvent}.
     *
     * @param anEvent the {@code KeyEvent} from which to
     *      obtain the {@code AWTKeyStroke}
     * @throws NullPointerException if {@code anEvent} is null
     * @return the {@code AWTKeyStroke} that precipitated the event
     */
    @SuppressWarnings("deprecation")
    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 {@code AWTKeyStroke}.
     * 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} object for that String
     * @throws IllegalArgumentException if {@code s} is {@code null},
     *        or is formatted incorrectly
     */
    @SuppressWarnings("deprecation")
    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 = 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
     * {@code key}. This will throw an
     * {@code IllegalArgumentException} if {@code key} 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 | IllegalAccessException e) {
                throw new IllegalArgumentException(errmsg);
            }
            value = Integer.valueOf(keyCode);
            vkCollect.put(key, value);
        }
        return value.intValue();
    }

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

    /**
     * Returns the numeric key code for this {@code AWTKeyStroke}.
     *
     * @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 {@code AWTKeyStroke}.
     *
     * @return an int containing the modifiers
     * @see #getAWTKeyStroke(int,int)
     */
    public final int getModifiers() {
        return modifiers;
    }

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

    /**
     * Returns the type of {@code KeyEvent} which corresponds to
     * this {@code AWTKeyStroke}.
     *
     * @return {@code KeyEvent.KEY_PRESSED},
     *         {@code KeyEvent.KEY_TYPED},
     *         or {@code KeyEvent.KEY_RELEASED}
     * @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.
     *
     * @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.
     *
     * @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 {@code String} returned by this method can be passed
     * as a parameter to {@code getAWTKeyStroke(String)} 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 {@code AWTKeyStroke} (or a subclass of
     * {@code AWTKeyStroke}) which is equal to this instance.
     *
     * @return a cached instance which is equal to this instance
     * @throws java.io.ObjectStreamException if a serialization problem occurs
     */
    @Serial
    protected Object readResolve() throws java.io.ObjectStreamException {
        synchronized (AWTKeyStroke.class) {

            return getCachedStroke(keyChar, keyCode, modifiers, onKeyRelease);
        }
    }

    @SuppressWarnings("deprecation")
    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;
    }

    @SuppressWarnings("deprecation")
    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 name2code.get(name);
    }

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