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 * Copyright (c) 1996, 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
 * 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.datatransfer;

import java.awt.EventQueue;

import java.util.Set;
import java.util.HashSet;
import java.util.Arrays;

import java.io.IOException;

import sun.awt.EventListenerAggregate;


A class that implements a mechanism to transfer data using
cut/copy/paste operations.

 FlavorListeners may be registered on an instance of the Clipboard class to be notified about changes to the set of DataFlavors available on this clipboard (see addFlavorListener). 
Author:     Amy Fowler,      Alexander Gerasimov
See Also:
/**
 * A class that implements a mechanism to transfer data using
 * cut/copy/paste operations.
 * <p>
 * {@link FlavorListener}s may be registered on an instance of the
 * Clipboard class to be notified about changes to the set of
 * {@link DataFlavor}s available on this clipboard (see
 * {@link #addFlavorListener}).
 *
 * @see java.awt.Toolkit#getSystemClipboard
 * @see java.awt.Toolkit#getSystemSelection
 *
 * @author      Amy Fowler
 * @author      Alexander Gerasimov
 */
public class Clipboard {

    String name;

    protected ClipboardOwner owner;
    protected Transferable contents;

    
An aggregate of flavor listeners registered on this local clipboard.

Since:1.5
/**
     * An aggregate of flavor listeners registered on this local clipboard.
     *
     * @since 1.5
     */
    private EventListenerAggregate flavorListeners;

    
A set of DataFlavors that is available on
this local clipboard. It is used for tracking changes
of DataFlavors available on this clipboard.

Since:1.5
/**
     * A set of <code>DataFlavor</code>s that is available on
     * this local clipboard. It is used for tracking changes
     * of <code>DataFlavor</code>s available on this clipboard.
     *
     * @since 1.5
     */
    private Set<DataFlavor> currentDataFlavors;

    
Creates a clipboard object.

See Also:
  • getSystemClipboard.getSystemClipboard
/**
     * Creates a clipboard object.
     *
     * @see java.awt.Toolkit#getSystemClipboard
     */
    public Clipboard(String name) {
        this.name = name;
    }

    
Returns the name of this clipboard object.

See Also:
  • getSystemClipboard.getSystemClipboard
/**
     * Returns the name of this clipboard object.
     *
     * @see java.awt.Toolkit#getSystemClipboard
     */
    public String getName() {
        return name;
    }

    
Sets the current contents of the clipboard to the specified
transferable object and registers the specified clipboard owner
as the owner of the new contents.


If there is an existing owner different from the argument
owner, that owner is notified that it no longer
holds ownership of the clipboard contents via an invocation
of ClipboardOwner.lostOwnership() on that owner.
An implementation of setContents() is free not
to invoke lostOwnership() directly from this method.
For example, lostOwnership() may be invoked later on
a different thread. The same applies to FlavorListeners
registered on this clipboard.


The method throws IllegalStateException if the clipboard
is currently unavailable. For example, on some platforms, the system
clipboard is unavailable while it is accessed by another application.

Params:
  • contents – the transferable object representing the
                clipboard content
  • owner – the object which owns the clipboard content
Throws:
See Also:
/**
     * Sets the current contents of the clipboard to the specified
     * transferable object and registers the specified clipboard owner
     * as the owner of the new contents.
     * <p>
     * If there is an existing owner different from the argument
     * <code>owner</code>, that owner is notified that it no longer
     * holds ownership of the clipboard contents via an invocation
     * of <code>ClipboardOwner.lostOwnership()</code> on that owner.
     * An implementation of <code>setContents()</code> is free not
     * to invoke <code>lostOwnership()</code> directly from this method.
     * For example, <code>lostOwnership()</code> may be invoked later on
     * a different thread. The same applies to <code>FlavorListener</code>s
     * registered on this clipboard.
     * <p>
     * The method throws <code>IllegalStateException</code> if the clipboard
     * is currently unavailable. For example, on some platforms, the system
     * clipboard is unavailable while it is accessed by another application.
     *
     * @param contents the transferable object representing the
     *                 clipboard content
     * @param owner the object which owns the clipboard content
     * @throws IllegalStateException if the clipboard is currently unavailable
     * @see java.awt.Toolkit#getSystemClipboard
     */
    public synchronized void setContents(Transferable contents, ClipboardOwner owner) {
        final ClipboardOwner oldOwner = this.owner;
        final Transferable oldContents = this.contents;

        this.owner = owner;
        this.contents = contents;

        if (oldOwner != null && oldOwner != owner) {
            EventQueue.invokeLater(new Runnable() {
                public void run() {
                    oldOwner.lostOwnership(Clipboard.this, oldContents);
                }
            });
        }
        fireFlavorsChanged();
    }

    
Returns a transferable object representing the current contents
of the clipboard.  If the clipboard currently has no contents,
it returns null. The parameter Object requestor is
not currently used.  The method throws
IllegalStateException if the clipboard is currently
unavailable.  For example, on some platforms, the system clipboard is
unavailable while it is accessed by another application.

Params:
  • requestor – the object requesting the clip data  (not used)
Throws:
See Also:
Returns:the current transferable object on the clipboard
/**
     * Returns a transferable object representing the current contents
     * of the clipboard.  If the clipboard currently has no contents,
     * it returns <code>null</code>. The parameter Object requestor is
     * not currently used.  The method throws
     * <code>IllegalStateException</code> if the clipboard is currently
     * unavailable.  For example, on some platforms, the system clipboard is
     * unavailable while it is accessed by another application.
     *
     * @param requestor the object requesting the clip data  (not used)
     * @return the current transferable object on the clipboard
     * @throws IllegalStateException if the clipboard is currently unavailable
     * @see java.awt.Toolkit#getSystemClipboard
     */
    public synchronized Transferable getContents(Object requestor) {
        return contents;
    }


    
Returns an array of DataFlavors in which the current
contents of this clipboard can be provided. If there are no
DataFlavors available, this method returns a zero-length
array.

Throws:
Returns:an array of DataFlavors in which the current
        contents of this clipboard can be provided
Since:1.5
/**
     * Returns an array of <code>DataFlavor</code>s in which the current
     * contents of this clipboard can be provided. If there are no
     * <code>DataFlavor</code>s available, this method returns a zero-length
     * array.
     *
     * @return an array of <code>DataFlavor</code>s in which the current
     *         contents of this clipboard can be provided
     *
     * @throws IllegalStateException if this clipboard is currently unavailable
     *
     * @since 1.5
     */
    public DataFlavor[] getAvailableDataFlavors() {
        Transferable cntnts = getContents(null);
        if (cntnts == null) {
            return new DataFlavor[0];
        }
        return cntnts.getTransferDataFlavors();
    }

    
Returns whether or not the current contents of this clipboard can be
provided in the specified DataFlavor.

Params:
  • flavor – the requested DataFlavor for the contents
Throws:
Returns:true if the current contents of this clipboard
        can be provided in the specified DataFlavor;
        false otherwise
Since:1.5
/**
     * Returns whether or not the current contents of this clipboard can be
     * provided in the specified <code>DataFlavor</code>.
     *
     * @param flavor the requested <code>DataFlavor</code> for the contents
     *
     * @return <code>true</code> if the current contents of this clipboard
     *         can be provided in the specified <code>DataFlavor</code>;
     *         <code>false</code> otherwise
     *
     * @throws NullPointerException if <code>flavor</code> is <code>null</code>
     * @throws IllegalStateException if this clipboard is currently unavailable
     *
     * @since 1.5
     */
    public boolean isDataFlavorAvailable(DataFlavor flavor) {
        if (flavor == null) {
            throw new NullPointerException("flavor");
        }

        Transferable cntnts = getContents(null);
        if (cntnts == null) {
            return false;
        }
        return cntnts.isDataFlavorSupported(flavor);
    }

    
Returns an object representing the current contents of this clipboard
in the specified DataFlavor.
The class of the object returned is defined by the representation
class of flavor.

Params:
  • flavor – the requested DataFlavor for the contents
Throws:
See Also:
Returns:an object representing the current contents of this clipboard
        in the specified DataFlavor
Since:1.5
/**
     * Returns an object representing the current contents of this clipboard
     * in the specified <code>DataFlavor</code>.
     * The class of the object returned is defined by the representation
     * class of <code>flavor</code>.
     *
     * @param flavor the requested <code>DataFlavor</code> for the contents
     *
     * @return an object representing the current contents of this clipboard
     *         in the specified <code>DataFlavor</code>
     *
     * @throws NullPointerException if <code>flavor</code> is <code>null</code>
     * @throws IllegalStateException if this clipboard is currently unavailable
     * @throws UnsupportedFlavorException if the requested <code>DataFlavor</code>
     *         is not available
     * @throws IOException if the data in the requested <code>DataFlavor</code>
     *         can not be retrieved
     *
     * @see DataFlavor#getRepresentationClass
     *
     * @since 1.5
     */
    public Object getData(DataFlavor flavor)
        throws UnsupportedFlavorException, IOException {
        if (flavor == null) {
            throw new NullPointerException("flavor");
        }

        Transferable cntnts = getContents(null);
        if (cntnts == null) {
            throw new UnsupportedFlavorException(flavor);
        }
        return cntnts.getTransferData(flavor);
    }


    
Registers the specified FlavorListener to receive
FlavorEvents from this clipboard.
If listener is null, no exception
is thrown and no action is performed.

Params:
  • listener – the listener to be added
See Also:
Since:1.5
/**
     * Registers the specified <code>FlavorListener</code> to receive
     * <code>FlavorEvent</code>s from this clipboard.
     * If <code>listener</code> is <code>null</code>, no exception
     * is thrown and no action is performed.
     *
     * @param listener the listener to be added
     *
     * @see #removeFlavorListener
     * @see #getFlavorListeners
     * @see FlavorListener
     * @see FlavorEvent
     * @since 1.5
     */
    public synchronized void addFlavorListener(FlavorListener listener) {
        if (listener == null) {
            return;
        }
        if (flavorListeners == null) {
            currentDataFlavors = getAvailableDataFlavorSet();
            flavorListeners = new EventListenerAggregate(FlavorListener.class);
        }
        flavorListeners.add(listener);
    }

    
Removes the specified FlavorListener so that it no longer
receives FlavorEvents from this Clipboard.
This method performs no function, nor does it throw an exception, if
the listener specified by the argument was not previously added to this
Clipboard.
If listener is null, no exception
is thrown and no action is performed.

Params:
  • listener – the listener to be removed
See Also:
Since:1.5
/**
     * Removes the specified <code>FlavorListener</code> so that it no longer
     * receives <code>FlavorEvent</code>s from this <code>Clipboard</code>.
     * This method performs no function, nor does it throw an exception, if
     * the listener specified by the argument was not previously added to this
     * <code>Clipboard</code>.
     * If <code>listener</code> is <code>null</code>, no exception
     * is thrown and no action is performed.
     *
     * @param listener the listener to be removed
     *
     * @see #addFlavorListener
     * @see #getFlavorListeners
     * @see FlavorListener
     * @see FlavorEvent
     * @since 1.5
     */
    public synchronized void removeFlavorListener(FlavorListener listener) {
        if (listener == null || flavorListeners == null) {
            return;
        }
        flavorListeners.remove(listener);
    }

    
Returns an array of all the FlavorListeners currently
registered on this Clipboard.

See Also:
Returns:all of this clipboard's FlavorListeners or an empty
        array if no listeners are currently registered
Since:1.5
/**
     * Returns an array of all the <code>FlavorListener</code>s currently
     * registered on this <code>Clipboard</code>.
     *
     * @return all of this clipboard's <code>FlavorListener</code>s or an empty
     *         array if no listeners are currently registered
     * @see #addFlavorListener
     * @see #removeFlavorListener
     * @see FlavorListener
     * @see FlavorEvent
     * @since 1.5
     */
    public synchronized FlavorListener[] getFlavorListeners() {
        return flavorListeners == null ? new FlavorListener[0] :
                (FlavorListener[])flavorListeners.getListenersCopy();
    }

    
Checks change of the DataFlavors and, if necessary,
notifies all listeners that have registered interest for notification
on FlavorEvents.

Since:1.5
/**
     * Checks change of the <code>DataFlavor</code>s and, if necessary,
     * notifies all listeners that have registered interest for notification
     * on <code>FlavorEvent</code>s.
     *
     * @since 1.5
     */
    private void fireFlavorsChanged() {
        if (flavorListeners == null) {
            return;
        }
        Set<DataFlavor> prevDataFlavors = currentDataFlavors;
        currentDataFlavors = getAvailableDataFlavorSet();
        if (prevDataFlavors.equals(currentDataFlavors)) {
            return;
        }
        FlavorListener[] flavorListenerArray =
                (FlavorListener[])flavorListeners.getListenersInternal();
        for (int i = 0; i < flavorListenerArray.length; i++) {
            final FlavorListener listener = flavorListenerArray[i];
            EventQueue.invokeLater(new Runnable() {
                public void run() {
                    listener.flavorsChanged(new FlavorEvent(Clipboard.this));
                }
            });
        }
    }

    
Returns a set of DataFlavors currently available
on this clipboard.

Returns:a set of DataFlavors currently available
        on this clipboard
Since:1.5
/**
     * Returns a set of <code>DataFlavor</code>s currently available
     * on this clipboard.
     *
     * @return a set of <code>DataFlavor</code>s currently available
     *         on this clipboard
     *
     * @since 1.5
     */
    private Set<DataFlavor> getAvailableDataFlavorSet() {
        Set<DataFlavor> set = new HashSet<>();
        Transferable contents = getContents(null);
        if (contents != null) {
            DataFlavor[] flavors = contents.getTransferDataFlavors();
            if (flavors != null) {
                set.addAll(Arrays.asList(flavors));
            }
        }
        return set;
    }
}