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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
 * 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).
 *
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 *
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package java.awt.datatransfer;

import java.io.IOException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

import sun.datatransfer.DataFlavorUtil;


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:
  • getSystemClipboard.getSystemClipboard
  • getSystemSelection.getSystemSelection
Since:1.1
/**
 * 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}).
 *
 * @author Amy Fowler
 * @author Alexander Gerasimov
 * @see java.awt.Toolkit#getSystemClipboard
 * @see java.awt.Toolkit#getSystemSelection
 * @since 1.1
 */
public class Clipboard {

    String name;

    
The owner of the clipboard.

/**
     * The owner of the clipboard.
     */
    protected ClipboardOwner owner;

    
Contents of the clipboard.

/**
     * Contents of the clipboard.
     */
    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 Set<FlavorListener> 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}s that is available on this local clipboard.
     * It is used for tracking changes of {@code DataFlavor}s available on this
     * clipboard.
     *
     * @since 1.5
     */
    private Set<DataFlavor> currentDataFlavors;

    
Creates a clipboard object.

Params:
  • name – for the clipboard
See Also:
  • getSystemClipboard.getSystemClipboard
/**
     * Creates a clipboard object.
     *
     * @param  name for the clipboard
     * @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
/**
     * Returns the name of this clipboard object.
     *
     * @return 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:
  • getSystemClipboard.getSystemClipboard
/**
     * 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},
     * that owner is notified that it no longer holds ownership of the clipboard
     * contents via an invocation of {@code ClipboardOwner.lostOwnership()} on
     * that owner. An implementation of {@code setContents()} is free not to
     * invoke {@code lostOwnership()} directly from this method. For example,
     * {@code lostOwnership()} may be invoked later on a different thread. The
     * same applies to {@code FlavorListener}s registered on this clipboard.
     * <p>
     * The method throws {@code IllegalStateException} 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) {
            DataFlavorUtil.getDesktopService().invokeOnEventThread(() ->
                    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:
  • getSystemClipboard.getSystemClipboard
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}. The parameter Object requestor is not currently used. The
     * method throws {@code IllegalStateException} 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}s in which the current contents of
     * this clipboard can be provided. If there are no {@code DataFlavor}s
     * available, this method returns a zero-length array.
     *
     * @return an array of {@code DataFlavor}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}.
     *
     * @param  flavor the requested {@code DataFlavor} for the contents
     * @return {@code true} if the current contents of this clipboard can be
     *         provided in the specified {@code DataFlavor}; {@code false}
     *         otherwise
     * @throws NullPointerException if {@code flavor} is {@code null}
     * @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}. The class of the object returned is
     * defined by the representation class of {@code flavor}.
     *
     * @param  flavor the requested {@code DataFlavor} for the contents
     * @return an object representing the current contents of this clipboard in
     *         the specified {@code DataFlavor}
     * @throws NullPointerException if {@code flavor} is {@code null}
     * @throws IllegalStateException if this clipboard is currently unavailable
     * @throws UnsupportedFlavorException if the requested {@code DataFlavor} is
     *         not available
     * @throws IOException if the data in the requested {@code DataFlavor} 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} to receive
     * {@code FlavorEvent}s from this clipboard. If {@code listener} is
     * {@code null}, 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) {
            flavorListeners = new HashSet<>();
            currentDataFlavors = getAvailableDataFlavorSet();
        }

        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} so that it no longer
     * receives {@code FlavorEvent}s from this {@code 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
     * {@code Clipboard}. If {@code listener} is {@code null}, 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}s currently registered
     * on this {@code Clipboard}.
     *
     * @return all of this clipboard's {@code FlavorListener}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] :
            flavorListeners.toArray(new FlavorListener[flavorListeners.size()]);
    }

    
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}s and, if necessary, notifies all
     * listeners that have registered interest for notification on
     * {@code FlavorEvent}s.
     *
     * @since 1.5
     */
    private void fireFlavorsChanged() {
        if (flavorListeners == null) {
            return;
        }

        Set<DataFlavor> prevDataFlavors = currentDataFlavors;
        currentDataFlavors = getAvailableDataFlavorSet();
        if (Objects.equals(prevDataFlavors, currentDataFlavors)) {
            return;
        }
        flavorListeners.forEach(listener ->
                DataFlavorUtil.getDesktopService().invokeOnEventThread(() ->
                        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}s currently available on this
     * clipboard.
     *
     * @return a set of {@code DataFlavor}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;
    }
}