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public interface ProgressListener {
    void updateProgress(long loaded, long total);
 
    boolean hasCancelled(); }
 
public abstract class DownloadListener implements ProgressListener {
 
    /**
     * Local file length for resuming download. 0 if local file not exist
     */
    public long getLocalLength() {
        return 0;
    }
 
    /**
     * Used for <tt>If-None-Match</tt> or <tt>If-Range</tt>. MD5 or <tt>null</tt> if not applicable or not known
     * @see <a href="http://tools.ietf.org/html/rfc2616#page-132">rfc 2616</a>
     */
    public String getETag() {
        return null;
    }
 
    /**
     * Start position after server response
     */
    public void setStartPosition(long position) {
    }
 
    /**
     * Content length after server response. 0 if not known
     * @throws DownloadNoSpaceAvailableException if no local space for content
     */
    public void setContentLength(long length)
        throws DownloadNoSpaceAvailableException {
    }
 
    public abstract OutputStream getOutputStream(boolean append)
            throws IOException;
 
    @Override
    public void updateProgress(long loaded, long total) {
    }
 
    @Override
    public boolean hasCancelled() {
        return false;
    }
 
    public void setETag(String etag) {
    }
 
    public void setContentType(String contentType) {
    } }
 
public class FileDownloadListener extends DownloadListener {
 
    private final File saveTo;
    private final ProgressListener progressListener;
 
    public FileDownloadListener(File saveTo, ProgressListener progressListener) {
        this.saveTo = saveTo;
        this.progressListener = progressListener;
    }
 
    @Override
    public OutputStream getOutputStream(boolean append)
            throws FileNotFoundException {
        return new FileOutputStream(saveTo, append);
    }
 
    @Override
    public long getLocalLength() {
        return saveTo.length();
    }
 
    @Override
    public void updateProgress(long loaded, long total) {
        if (progressListener != null) {
            progressListener.updateProgress(loaded, total);
        }
    }
 
    @Override
    public boolean hasCancelled() {
        return progressListener != null && progressListener.hasCancelled();
    } 
}