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/*
 * @(#)Checkbox.java  1.59 06/10/10
 *
 * Copyright  1990-2006 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program 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 program 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 at /legal/license.txt). 
 * 
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions. 
 *
 */
package java.awt;

import sun.awt.peer.CheckboxPeer;
import sun.awt.PeerBasedToolkit;
import java.awt.event.*;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;
import java.util.EventListener;
import java.awt.AWTEventMulticaster;

/**
 * A check box is a graphical component that can be in either an
 * "on" (<code>true</code>) or "off" (<code>false</code>) state.
 * Clicking on a check box changes its state from
 * "on" to "off," or from "off" to "on."
 * <p>
 * The following code example creates a set of check boxes in
 * a grid layout:
 * <p>
 * <hr><blockquote><pre>
 * setLayout(new GridLayout(3, 1));
 * add(new Checkbox("one", null, true));
 * add(new Checkbox("two"));
 * add(new Checkbox("three"));
 * </pre></blockquote><hr>
 * <p>
 * This image depicts the check boxes and grid layout
 * created by this code example:
 * <p>
 * <img src="images-awt/Checkbox-1.gif"
 * ALIGN=center HSPACE=10 VSPACE=7>
 * <p>
 * The button labeled <code>one</code> is in the "on" state, and the
 * other two are in the "off" state. In this example, which uses the
 * <code>GridLayout</code> class, the states of the three check
 * boxes are set independently.
 * <p>
 * Alternatively, several check boxes can be grouped together under
 * the control of a single object, using the
 * <code>CheckboxGroup</code> class.
 * In a check box group, at most one button can be in the "on"
 * state at any given time. Clicking on a check box to turn it on
 * forces any other check box in the same group that is on
 * into the "off" state.
 *
 * @version  1.51 08/19/02
 * @author   Sami Shaio
 * @see         java.awt.GridLayout
 * @see         java.awt.CheckboxGroup
 * @since       JDK1.0
 */
public class Checkbox extends Component implements ItemSelectable {
    /**
     * The label of the Checkbox.
     */
    String label;
    /**
     * The state of the Checkbox.
     */
    boolean state;
    /**
     * The check box group.
     */
    CheckboxGroup group;
    transient ItemListener itemListener;
    private static final String base = "checkbox";
    private static int nameCounter = 0;
    /*
     * JDK 1.1 serialVersionUID
     */
    private static final long serialVersionUID = 7270714317450821763L;
    /**
     * Helper function for setState and CheckboxGroup.setSelectedCheckbox
     * Should remain package-private.
     */
    void setStateInternal(boolean state) {
        this.state = state;
        CheckboxPeer peer = (CheckboxPeer) this.peer;
        if (peer != null) {
            peer.setState(state);
        }
    }

    /**
     * Creates a check box with no label. The state of this
     * check box is set to "off," and it is not part of any
     * check box group.
     * @since     JDK1.0
     */
    public Checkbox() {
        this("", false, null);
    }

    /**
     * Creates a check box with the specified label.  The state
     * of this check box is set to "off," and it is not part of
     * any check box group.
     * @param     label   a string label for this check box,
     *                        or <code>null</code> for no label.
     * @since     JDK1.0
     */
    public Checkbox(String label) {
        this(label, false, null);
    }

    /**
     * Creates a check box with the specified label.  The state
     * of this check box is as specified by the <code>state</code>
     * argument, and it is not part of any check box group.
     * @param     label   a string label for this check box,
     *                        or <code>null</code> for no label.
     * @param     state    the initial state of this check box.
     * @since     JDK1.0
     */
    public Checkbox(String label, boolean state) {
        this(label, state, null);
    }

    /**
     * Creates a check box with the specified label, in the specified
     * check box group, and set to the specified state.

     * @param     label   a string label for this check box,
     *                        or <code>null</code> for no label.
     * @param     state   the initial state of this check box.
     * @param     group   a check box group for this check box,
     *                           or <code>null</code> for no group.
     * @since     JDK1.1
     */
    public Checkbox(String label, boolean state, CheckboxGroup group) {
        this.label = label;
        this.state = state;
        this.group = group;
        if (state && (group != null)) {
            group.setSelectedCheckbox(this);
        }
    }

    /**
     * Constructs a Checkbox with the specified label, set to the
     * specified state, and in the specified check box group.
     */
    public Checkbox(String label, CheckboxGroup group, boolean state) {
        this(label, state, group);
    }

    /**
     * Construct a name for this component.  Called by getName() when the
     * name is null.
     */
    String constructComponentName() {
        return base + nameCounter++;
    }

    /**
     * Creates the peer of the Checkbox. The peer allows you to change the
     * look of the Checkbox without changing its functionality.
     * @see     java.awt.Toolkit#createCheckbox(java.awt.Checkbox)
     * @see     java.awt.Component#getToolkit()
     * @since   JDK1.0
     */
    public void addNotify() {
        synchronized (getTreeLock()) {
            if (peer == null)
                peer = ((PeerBasedToolkit) getToolkit()).createCheckbox(this);
            super.addNotify();
        }
    }

    /**
     * Gets the label of this check box.
     * @return   the label of this check box, or <code>null</code>
     *                  if this check box has no label.
     * @see      java.awt.Checkbox#setLabel
     * @since    JDK1.0
     */
    public String getLabel() {
        return label;
    }

    /**
     * Sets this check box's label to be the string argument.
     * @param    label   a string to set as the new label, or
     *                        <code>null</code> for no label.
     * @see      java.awt.Checkbox#getLabel
     * @since    JDK1.0
     */
    public synchronized void setLabel(String label) {
        this.label = label;
        CheckboxPeer peer = (CheckboxPeer) this.peer;
        if (peer != null) {
            peer.setLabel(label);
        }
    }

    /**
     * Determines whether this check box is in the "on" or "off" state.
     * The boolean value <code>true</code> indicates the "on" state,
     * and <code>false</code> indicates the "off" state.
     * @return    the state of this check box, as a boolean value.
     * @see       java.awt.Checkbox#setState
     * @since     JDK1.0
     */
    public boolean getState() {
        return state;
    }
  
    /**
     * Sets the state of this check box to the specified state.
     * The boolean value <code>true</code> indicates the "on" state,
     * and <code>false</code> indicates the "off" state.
     * @param     state   the boolean state of the check box.
     * @see       java.awt.Checkbox#getState
     * @since     JDK1.0
     */
    public void setState(boolean state) {
        /* Cannot hold check box lock when calling group.setSelectedCheckbox. */
        CheckboxGroup group = this.group;
        if (group != null) {
            if (state) {
                group.setSelectedCheckbox(this);
            } else if (group.getSelectedCheckbox() == this) {
                state = true;
            }
        }
        setStateInternal(state);
    }

    /**
     * Returns the an array (length 1) containing the checkbox
     * label or null if the checkbox is not selected.
     * @see ItemSelectable
     */
    public Object[] getSelectedObjects() {
        if (state) {
            Object[] items = new Object[1];
            items[0] = label;
            return items;
        }
        return null;
    }

    /**
     * Determines this check box's group.
     * @return     this check box's group, or <code>null</code>
     *               if the check box is not part of a check box group.
     * @see        java.awt.Checkbox#setCheckboxGroup
     * @since      JDK1.0
     */
    public CheckboxGroup getCheckboxGroup() {
        return group;
    }

    /**
     * Sets this check box's group to be the specified check box group.
     * If this check box is already in a different check box group,
     * it is first taken out of that group.
     * @param     g   the new check box group, or <code>null</code>
     *                to remove this check box from any check box group.
     * @see       java.awt.Checkbox#getCheckboxGroup
     * @since     JDK1.0
     */
    public void setCheckboxGroup(CheckboxGroup g) {
        // 6257119 : Brought over the code from j2se 1.4.2 to fix the 
        // bug
        CheckboxGroup oldGroup;
        boolean oldState;

        /* Do nothing if this check box has already belonged
         * to the check box group g.
         */
        if (this.group == g) {
            return;
        }

      synchronized (this) {
            oldGroup = this.group;
            oldState = getState();

          this.group = g;
          CheckboxPeer peer = (CheckboxPeer)this.peer;
          if (peer != null) {
            peer.setCheckboxGroup(g);
          }
          if (this.group != null && getState()) {
              if (this.group.getSelectedCheckbox() != null) {
                  setState(false);
              } else {
                  this.group.setSelectedCheckbox(this);
              }
          }
      }

        /* Locking check box below could cause deadlock with
         * CheckboxGroup's setSelectedCheckbox method.
         *
         * Fix for 4726853 by kdm@sparc.spb.su
         * Here we should check if this check box was selected
         * in the previous group and set selected check box to
         * null for that group if so.
         */
        if (oldGroup != null && oldState) {
            oldGroup.setSelectedCheckbox(null);
        }
        // 6257119
    }
    
    /**
     * Adds the specified item listener to receive item events from
     * this check box.
     * @param         l    the item listener.
     * @see           java.awt.event.ItemEvent
     * @see           java.awt.event.ItemListener
     * @see           java.awt.Checkbox#removeItemListener
     * @since         JDK1.1
     */
    public synchronized void addItemListener(ItemListener l) {
        itemListener = AWTEventMulticaster.add(itemListener, l);
        newEventsOnly = true;
    }

    /**
     * Removes the specified item listener so that the item listener
     * no longer receives item events from this check box.
     * @param         l    the item listener.
     * @see           java.awt.event.ItemEvent
     * @see           java.awt.event.ItemListener
     * @see           java.awt.Checkbox#addItemListener
     * @since         JDK1.1
     */
    public synchronized void removeItemListener(ItemListener l) {
        itemListener = AWTEventMulticaster.remove(itemListener, l);
    }

    /**
     * Returns an array of all the item listeners
     * registered on this checkbox.
     *
     * @return all of this checkbox's <code>ItemListener</code>s
     *         or an empty array if no item
     *         listeners are currently registered
     *
     * @see           #addItemListener
     * @see           #removeItemListener
     * @see           java.awt.event.ItemEvent
     * @see           java.awt.event.ItemListener
     * @since 1.4
     */
    public synchronized ItemListener[] getItemListeners() {
        return (ItemListener[]) AWTEventMulticaster.getListeners(
                                (EventListener)itemListener,
                                ItemListener.class);
    }

    // REMIND: remove when filtering is done at lower level
    boolean eventEnabled(AWTEvent e) {
        if (e.id == ItemEvent.ITEM_STATE_CHANGED) {
            if ((eventMask & AWTEvent.ITEM_EVENT_MASK) != 0 ||
                itemListener != null) {
                return true;
            }
            return false;
        }
        return super.eventEnabled(e);
    }

    /**
     * Processes events on this check box.
     * If the event is an instance of <code>ItemEvent</code>,
     * this method invokes the <code>processItemEvent</code> method.
     * Otherwise, it calls its superclass's <code>processEvent</code> method.
     * @param         e the event.
     * @see           java.awt.event.ItemEvent
     * @see           java.awt.Checkbox#processItemEvent
     * @since         JDK1.1
     */
    protected void processEvent(AWTEvent e) {
        if (e instanceof ItemEvent) {
            processItemEvent((ItemEvent) e);
            return;
        }
        super.processEvent(e);
    }

    /**
     * Processes item events occurring on this check box by
     * dispatching them to any registered
     * <code>ItemListener</code> objects.
     * <p>
     * This method is not called unless item events are
     * enabled for this component. Item events are enabled
     * when one of the following occurs:
     * <p><ul>
     * <li>An <code>ItemListener</code> object is registered
     * via <code>addItemListener</code>.
     * <li>Item events are enabled via <code>enableEvents</code>.
     * </ul>
     * @param       e the item event.
     * @see         java.awt.event.ItemEvent
     * @see         java.awt.event.ItemListener
     * @see         java.awt.Checkbox#addItemListener
     * @see         java.awt.Component#enableEvents
     * @since       JDK1.1
     */
    protected void processItemEvent(ItemEvent e) {
        if (itemListener != null) {
            itemListener.itemStateChanged(e);
        }
    }

    /**
     * Returns the parameter string representing the state of
     * this check box. This string is useful for debugging.
     * @return    the parameter string of this check box.
     * @since     JDK1.0
     */
    protected String paramString() {
        String str = super.paramString();
        String label = this.label;
        if (label != null) {
            str += ",label=" + label;
        }
        return str + ",state=" + state;
    }
    /* Serialization support.
     */

    private int checkboxSerializedDataVersion = 1;
    private void writeObject(ObjectOutputStream s)
        throws java.io.IOException {
        s.defaultWriteObject();
        AWTEventMulticaster.save(s, itemListenerK, itemListener);
        s.writeObject(null);
    }

    private void readObject(ObjectInputStream s)
        throws ClassNotFoundException, IOException {
        s.defaultReadObject();
        Object keyOrNull;
        while (null != (keyOrNull = s.readObject())) {
            String key = ((String) keyOrNull).intern();
            if (itemListenerK == key)
                addItemListener((ItemListener) (s.readObject()));
            else // skip value for unrecognized key
                s.readObject();
        }
    }
}
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