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    1   /*
    2    * Copyright (c) 1995, 2007, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   package java.awt;
   26   
   27   import javax.accessibility;
   28   
   29   /**
   30    * <code>Panel</code> is the simplest container class. A panel
   31    * provides space in which an application can attach any other
   32    * component, including other panels.
   33    * <p>
   34    * The default layout manager for a panel is the
   35    * <code>FlowLayout</code> layout manager.
   36    *
   37    * @author      Sami Shaio
   38    * @see     java.awt.FlowLayout
   39    * @since   JDK1.0
   40    */
   41   public class Panel extends Container implements Accessible {
   42       private static final String base = "panel";
   43       private static int nameCounter = 0;
   44   
   45       /*
   46        * JDK 1.1 serialVersionUID
   47        */
   48        private static final long serialVersionUID = -2728009084054400034L;
   49   
   50       /**
   51        * Creates a new panel using the default layout manager.
   52        * The default layout manager for all panels is the
   53        * <code>FlowLayout</code> class.
   54        */
   55       public Panel() {
   56           this(new FlowLayout());
   57       }
   58   
   59       /**
   60        * Creates a new panel with the specified layout manager.
   61        * @param layout the layout manager for this panel.
   62        * @since JDK1.1
   63        */
   64       public Panel(LayoutManager layout) {
   65           setLayout(layout);
   66       }
   67   
   68       /**
   69        * Construct a name for this component.  Called by getName() when the
   70        * name is null.
   71        */
   72       String constructComponentName() {
   73           synchronized (Panel.class) {
   74               return base + nameCounter++;
   75           }
   76       }
   77   
   78       /**
   79        * Creates the Panel's peer.  The peer allows you to modify the
   80        * appearance of the panel without changing its functionality.
   81        */
   82   
   83       public void addNotify() {
   84           synchronized (getTreeLock()) {
   85               if (peer == null)
   86                   peer = getToolkit().createPanel(this);
   87               super.addNotify();
   88           }
   89       }
   90   
   91   /////////////////
   92   // Accessibility support
   93   ////////////////
   94   
   95       /**
   96        * Gets the AccessibleContext associated with this Panel.
   97        * For panels, the AccessibleContext takes the form of an
   98        * AccessibleAWTPanel.
   99        * A new AccessibleAWTPanel instance is created if necessary.
  100        *
  101        * @return an AccessibleAWTPanel that serves as the
  102        *         AccessibleContext of this Panel
  103        * @since 1.3
  104        */
  105       public AccessibleContext getAccessibleContext() {
  106           if (accessibleContext == null) {
  107               accessibleContext = new AccessibleAWTPanel();
  108           }
  109           return accessibleContext;
  110       }
  111   
  112       /**
  113        * This class implements accessibility support for the
  114        * <code>Panel</code> class.  It provides an implementation of the
  115        * Java Accessibility API appropriate to panel user-interface elements.
  116        * @since 1.3
  117        */
  118       protected class AccessibleAWTPanel extends AccessibleAWTContainer {
  119   
  120           private static final long serialVersionUID = -6409552226660031050L;
  121   
  122           /**
  123            * Get the role of this object.
  124            *
  125            * @return an instance of AccessibleRole describing the role of the
  126            * object
  127            */
  128           public AccessibleRole getAccessibleRole() {
  129               return AccessibleRole.PANEL;
  130           }
  131       }
  132   
  133   }

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