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Java FTP client, Java FTP NIO file system, Groovy FTP client
There is a newer version: 2.6.0
package org.xbib.io.ftp.client;

import java.util.EventListener;

/**
 * The CopyStreamAdapter will relay CopyStreamEvents to a list of listeners
 * when either of its bytesTransferred() methods are called.  Its purpose
 * is to facilitate the notification of the progress of a copy operation
 * performed by one of the static copyStream() methods in
 * {@link Util} to multiple listeners.  The static
 * copyStream() methods invoke the
 * bytesTransfered(long, int) of a CopyStreamListener for performance
 * reasons and also because multiple listeners cannot be registered given
 * that the methods are static.
 *
 * @see CopyStreamEvent
 * @see CopyStreamListener
 * @see Util
 */
public class CopyStreamAdapter implements CopyStreamListener {
    private final ListenerList internalListeners;

    /**
     * Creates a new copyStreamAdapter.
     */
    public CopyStreamAdapter() {
        internalListeners = new ListenerList();
    }

    /**
     * This method is invoked by a CopyStreamEvent source after copying
     * a block of bytes from a stream.  The CopyStreamEvent will contain
     * the total number of bytes transferred so far and the number of bytes
     * transferred in the last write.  The CopyStreamAdapater will relay
     * the event to all of its registered listeners, listing itself as the
     * source of the event.
     *
     * @param event The CopyStreamEvent fired by the copying of a block of
     *              bytes.
     */
    @Override
    public void bytesTransferred(CopyStreamEvent event) {
        for (EventListener listener : internalListeners) {
            ((CopyStreamListener) (listener)).bytesTransferred(event);
        }
    }

    /**
     * This method is not part of the JavaBeans model and is used by the
     * static methods in the {@link Util} class for efficiency.
     * It is invoked after a block of bytes to inform the listener of the
     * transfer.  The CopyStreamAdapater will create a CopyStreamEvent
     * from the arguments and relay the event to all of its registered
     * listeners, listing itself as the source of the event.
     *
     * @param totalBytesTransferred The total number of bytes transferred
     *                              so far by the copy operation.
     * @param bytesTransferred      The number of bytes copied by the most recent
     *                              write.
     * @param streamSize            The number of bytes in the stream being copied.
     *                              This may be equal to CopyStreamEvent.UNKNOWN_STREAM_SIZE if
     *                              the size is unknown.
     */
    @Override
    public void bytesTransferred(long totalBytesTransferred,
                                 int bytesTransferred, long streamSize) {
        for (EventListener listener : internalListeners) {
            ((CopyStreamListener) (listener)).bytesTransferred(
                    totalBytesTransferred, bytesTransferred, streamSize);
        }
    }

    /**
     * Registers a CopyStreamListener to receive CopyStreamEvents.
     * Although this method is not declared to be synchronized, it is
     * implemented in a thread safe manner.
     *
     * @param listener The CopyStreamlistener to register.
     */
    public void addCopyStreamListener(CopyStreamListener listener) {
        internalListeners.addListener(listener);
    }

    /**
     * Unregisters a CopyStreamListener.  Although this method is not
     * synchronized, it is implemented in a thread safe manner.
     *
     * @param listener The CopyStreamlistener to unregister.
     */
    public void removeCopyStreamListener(CopyStreamListener listener) {
        internalListeners.removeListener(listener);
    }
}