Download.java

import java.io.*;
import java.net.*;
import java.util.*;

class Download extends Observable implements Runnable {
	private static final int MAX_BUFFER_SIZE = 1024;
	public static final String STATUSES[] = {"Downloading", "Paused", "Complete", "Cancelled", "Error"};
	public static final int DOWNLOADING = 0;
	public static final int PAUSED = 1;
	public static final int COMPLETE = 2;
	public static final int CANCELLED = 3;
	public static final int ERROR = 4;
	private URL url;
	private int size;
	private int downloaded;
	private int status;
	
	public Download(URL url) {
		this.url = url;
		size = -1;
		downloaded = 0;
		status = DOWNLOADING;
		
		download();
	}
	
	public String getUrl() {
		return url.toString();
	}
	
	public int getSize() {
		return size;
	}
	
	public float getProgress() {
		return ((float) downloaded / size) * 100;
	
	}
	
	public int getStatus() {
		return status;
	}
	
	public void pause() {
		status = PAUSED;
		stateChanged();
	}
	
	public void resume() {
		status = DOWNLOADING;
		stateChanged();
		download();
	}
	
	public void cancel() {
		status = CANCELLED;
		stateChanged();
	}
	
	private void error() {
		status = ERROR;
		stateChanged();
	}
	
	private void download() {
		Thread thread = new Thread(this);
		thread.start();
	}
	
	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", "bytes=" + 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) {
				}
			}
		}
	}
	
	private void stateChanged() {
		setChanged();
		notifyObservers();
	}
}