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class Download extends Observable implements Runnable {
	  private static final int MAX_BUFFER_SIZE = 1024;
	
	  public static final int DOWNLOADING = 0;
	  public static final int COMPLETE = 1;
	
	  private URL url; 
	  private int size; 
	  private int downloaded; 
	  private int status; 
	  /**
	   * 
	   * @param url
	   */
	  public Download(URL url) {
		this.url = url;
		size = -1;
		downloaded = 0;
		status = DOWNLOADING;
		
		download();
	  }
	  /**
	   * 
	   */
	  private void download() {
	    Thread thread = new Thread(this);
	    thread.start();
	  }
	  /**
	   * 
	   * @param url
	   * @return
	   */
	  private String getFileName(URL url) {
	    String fileName = url.getFile();
	    return fileName.substring(fileName.lastIndexOf('/') + 1);
	  }
	  /**
	   * 
	   */
	  public void run() {
	    RandomAccessFile file = null;
	    InputStream stream = null;
	
	    try {
	      HttpURLConnection connection =
	        (HttpURLConnection) url.openConnection();
	      connection.setRequestProperty("Range",
	    downloaded + "-");
	
	  connection.connect();
	
	  if (connection.getResponseCode() / 100 != 2) {
	    //error();
	  }
	
	  int contentLength = connection.getContentLength();
	  if (contentLength < 1) {
	    //error();
	  }
	
	  if (size == -1) {
	    size = contentLength;
	    stateChanged();
	  }
	
	  file = new RandomAccessFile(getFileName(url), "rw");
	  file.seek(downloaded);
	
	  stream = connection.getInputStream();
	  while (status == DOWNLOADING) {
	    byte buffer[];
	    if (size - downloaded > MAX_BUFFER_SIZE) {
	      buffer = new byte[MAX_BUFFER_SIZE];
	    } else {
	      buffer = new byte[size - downloaded];
	    }
	
	    int read = stream.read(buffer);
	    if (read == -1)
	      break;
	
	    file.write(buffer, 0, read);
	    downloaded += read;
	    stateChanged();
	  }
	
	  if(status == DOWNLOADING) {
	    status = COMPLETE;
	    stateChanged();
	  }
	} catch(Exception e) {
	  //error();
	} finally {
	  if (file != null) 
	    try {
	      file.close();
	    } catch (Exception e) {
	    	// ...
	    }      
	
	  if (stream != null) 
	    try {
	      stream.close();
	    } catch (Exception e) {
	    	// ...
	        }      
	    }
	  }
	
	  // Notify observers that this download's status has changed.
	  private void stateChanged() {
	    // ...
	  }
}
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