JDK8/Java8源码在线阅读

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * 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).
 *
 * 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.event;

import java.awt.AWTEvent;
import java.awt.Event;
import java.lang.annotation.Native;

/**
 * A semantic event which indicates that a component-defined action occurred.
 * This high-level event is generated by a component (such as a
 * <code>Button</code>) when
 * the component-specific action occurs (such as being pressed).
 * The event is passed to every <code>ActionListener</code> object
 * that registered to receive such events using the component's
 * <code>addActionListener</code> method.
 * <p>
 * <b>Note:</b> To invoke an <code>ActionEvent</code> on a
 * <code>Button</code> using the keyboard, use the Space bar.
 * <P>
 * The object that implements the <code>ActionListener</code> interface
 * gets this <code>ActionEvent</code> when the event occurs. The listener
 * is therefore spared the details of processing individual mouse movements
 * and mouse clicks, and can instead process a "meaningful" (semantic)
 * event like "button pressed".
 * <p>
 * An unspecified behavior will be caused if the {@code id} parameter
 * of any particular {@code ActionEvent} instance is not
 * in the range from {@code ACTION_FIRST} to {@code ACTION_LAST}.
 *
 * @see ActionListener
 * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/actionlistener.html">Tutorial: How to Write an Action Listener</a>
 *
 * @author Carl Quinn
 * @since 1.1
 */
public class ActionEvent extends AWTEvent {

    /**
     * The shift modifier. An indicator that the shift key was held
     * down during the event.
     */
    public static final int SHIFT_MASK          = Event.SHIFT_MASK;

    /**
     * The control modifier. An indicator that the control key was held
     * down during the event.
     */
    public static final int CTRL_MASK           = Event.CTRL_MASK;

    /**
     * The meta modifier. An indicator that the meta key was held
     * down during the event.
     */
    public static final int META_MASK           = Event.META_MASK;

    /**
     * The alt modifier. An indicator that the alt key was held
     * down during the event.
     */
    public static final int ALT_MASK            = Event.ALT_MASK;


    /**
     * The first number in the range of ids used for action events.
     */
    public static final int ACTION_FIRST                = 1001;

    /**
     * The last number in the range of ids used for action events.
     */
    public static final int ACTION_LAST                 = 1001;

    /**
     * This event id indicates that a meaningful action occurred.
     */
    @Native public static final int ACTION_PERFORMED    = ACTION_FIRST; //Event.ACTION_EVENT

    /**
     * The nonlocalized string that gives more details
     * of what actually caused the event.
     * This information is very specific to the component
     * that fired it.

     * @serial
     * @see #getActionCommand
     */
    String actionCommand;

    /**
     * Timestamp of when this event occurred. Because an ActionEvent is a high-
     * level, semantic event, the timestamp is typically the same as an
     * underlying InputEvent.
     *
     * @serial
     * @see #getWhen
     */
    long when;

    /**
     * This represents the key modifier that was selected,
     * and is used to determine the state of the selected key.
     * If no modifier has been selected it will default to
     * zero.
     *
     * @serial
     * @see #getModifiers
     */
    int modifiers;

    /*
     * JDK 1.1 serialVersionUID
     */
    private static final long serialVersionUID = -7671078796273832149L;

    /**
     * Constructs an <code>ActionEvent</code> object.
     * <p>
     * This method throws an
     * <code>IllegalArgumentException</code> if <code>source</code>
     * is <code>null</code>.
     * A <code>null</code> <code>command</code> string is legal,
     * but not recommended.
     *
     * @param source  The object that originated the event
     * @param id      An integer that identifies the event.
     *                     For information on allowable values, see
     *                     the class description for {@link ActionEvent}
     * @param command A string that may specify a command (possibly one
     *                of several) associated with the event
     * @throws IllegalArgumentException if <code>source</code> is null
     * @see #getSource()
     * @see #getID()
     * @see #getActionCommand()
     */
    public ActionEvent(Object source, int id, String command) {
        this(source, id, command, 0);
    }

    /**
     * Constructs an <code>ActionEvent</code> object with modifier keys.
     * <p>
     * This method throws an
     * <code>IllegalArgumentException</code> if <code>source</code>
     * is <code>null</code>.
     * A <code>null</code> <code>command</code> string is legal,
     * but not recommended.
     *
     * @param source  The object that originated the event
     * @param id      An integer that identifies the event.
     *                     For information on allowable values, see
     *                     the class description for {@link ActionEvent}
     * @param command A string that may specify a command (possibly one
     *                of several) associated with the event
     * @param modifiers The modifier keys down during event
     *                  (shift, ctrl, alt, meta).
     *                  Passing negative parameter is not recommended.
     *                  Zero value means that no modifiers were passed
     * @throws IllegalArgumentException if <code>source</code> is null
     * @see #getSource()
     * @see #getID()
     * @see #getActionCommand()
     * @see #getModifiers()
     */
    public ActionEvent(Object source, int id, String command, int modifiers) {
        this(source, id, command, 0, modifiers);
    }

    /**
     * Constructs an <code>ActionEvent</code> object with the specified
     * modifier keys and timestamp.
     * <p>
     * This method throws an
     * <code>IllegalArgumentException</code> if <code>source</code>
     * is <code>null</code>.
     * A <code>null</code> <code>command</code> string is legal,
     * but not recommended.
     *
     * @param source    The object that originated the event
     * @param id      An integer that identifies the event.
     *                     For information on allowable values, see
     *                     the class description for {@link ActionEvent}
     * @param command A string that may specify a command (possibly one
     *                of several) associated with the event
     * @param modifiers The modifier keys down during event
     *                  (shift, ctrl, alt, meta).
     *                  Passing negative parameter is not recommended.
     *                  Zero value means that no modifiers were passed
     * @param when   A long that gives the time the event occurred.
     *               Passing negative or zero value
     *               is not recommended
     * @throws IllegalArgumentException if <code>source</code> is null
     * @see #getSource()
     * @see #getID()
     * @see #getActionCommand()
     * @see #getModifiers()
     * @see #getWhen()
     *
     * @since 1.4
     */
    public ActionEvent(Object source, int id, String command, long when,
                       int modifiers) {
        super(source, id);
        this.actionCommand = command;
        this.when = when;
        this.modifiers = modifiers;
    }

    /**
     * Returns the command string associated with this action.
     * This string allows a "modal" component to specify one of several
     * commands, depending on its state. For example, a single button might
     * toggle between "show details" and "hide details". The source object
     * and the event would be the same in each case, but the command string
     * would identify the intended action.
     * <p>
     * Note that if a <code>null</code> command string was passed
     * to the constructor for this <code>ActionEvent</code>, this
     * this method returns <code>null</code>.
     *
     * @return the string identifying the command for this event
     */
    public String getActionCommand() {
        return actionCommand;
    }

    /**
     * Returns the timestamp of when this event occurred. Because an

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