import java.awt.BorderLayout; import java.awt.Component; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.io.File; import java.io.FileOutputStream; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; import java.util.ArrayList; import java.util.Observable; import java.util.Observer; import java.util.Properties; import javax.swing.BorderFactory; import javax.swing.JButton; import javax.swing.JFileChooser; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JProgressBar; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.JTextField; import javax.swing.ListSelectionModel; import javax.swing.event.ListSelectionEvent; import javax.swing.event.ListSelectionListener; import javax.swing.table.AbstractTableModel; import javax.swing.table.TableCellRenderer;

public class DownloadManager extends JFrame implements Observer { private JTextField addTextField = new JTextField(30);

private DownloadsTableModel tableModel = new DownloadsTableModel();

private JTable table;

private JButton pauseButton = new JButton("Pause");

private JButton resumeButton = new JButton("Resume");

private JButton cancelButton, clearButton;

private JLabel saveFileLabel = new JLabel();

private Download selectedDownload;

private boolean clearing;

public DownloadManager() { setTitle("Marvin's Download Manager"); setSize(640, 480); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); fileMenu.setMnemonic(KeyEvent.VK_F); JMenuItem fileExitMenuItem = new JMenuItem("Exit", KeyEvent.VK_X); fileExitMenuItem.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { System.exit(0); } }); fileMenu.add(fileExitMenuItem); menuBar.add(fileMenu); setJMenuBar(menuBar);

// Set up add panel. JPanel addPanel = new JPanel(new BorderLayout());

JPanel targetPanel = new JPanel(new BorderLayout()); targetPanel.add(addTextField, BorderLayout.WEST); JButton addButton = new JButton("Add Download"); addButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionAdd(); } });

targetPanel.add(addButton, BorderLayout.EAST);

JPanel destinationPanel = new JPanel(new BorderLayout()); saveFileLabel.setText("File:"); destinationPanel.add(saveFileLabel, BorderLayout.WEST);

JButton saveFileButton = new JButton("Download To"); saveFileButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionSaveTo(); } }); destinationPanel.add(saveFileButton, BorderLayout.EAST); addPanel.add(destinationPanel, BorderLayout.NORTH); addPanel.add(targetPanel, BorderLayout.SOUTH);

// Set up Downloads table.

table = new JTable(tableModel); table.getSelectionModel().addListSelectionListener(new ListSelectionListener() { public void valueChanged(ListSelectionEvent e) { tableSelectionChanged(); } }); table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

ProgressRenderer renderer = new ProgressRenderer(0, 100); renderer.setStringPainted(true); // show progress text table.setDefaultRenderer(JProgressBar.class, renderer);

table.setRowHeight((int) renderer.getPreferredSize().getHeight());

JPanel downloadsPanel = new JPanel(); downloadsPanel.setBorder(BorderFactory.createTitledBorder("Downloads")); downloadsPanel.setLayout(new BorderLayout()); downloadsPanel.add(new JScrollPane(table), BorderLayout.CENTER);

JPanel buttonsPanel = new JPanel();

pauseButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionPause(); } }); pauseButton.setEnabled(false); buttonsPanel.add(pauseButton);

resumeButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionResume(); } }); resumeButton.setEnabled(false); buttonsPanel.add(resumeButton); cancelButton = new JButton("Cancel"); cancelButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionCancel(); } }); cancelButton.setEnabled(false); buttonsPanel.add(cancelButton); clearButton = new JButton("Clear"); clearButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionClear(); } }); clearButton.setEnabled(false); buttonsPanel.add(clearButton);

getContentPane().setLayout(new BorderLayout()); getContentPane().add(addPanel, BorderLayout.NORTH); getContentPane().add(downloadsPanel, BorderLayout.CENTER); getContentPane().add(buttonsPanel, BorderLayout.SOUTH); }

private void actionSaveTo() {

JFileChooser jfchooser = new JFileChooser();

jfchooser.setApproveButtonText("OK"); jfchooser.setDialogTitle("Save To"); jfchooser.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);

int result = jfchooser.showOpenDialog(this); File newZipFile = jfchooser.getSelectedFile(); System.out.println("importProfile:" + newZipFile); this.saveFileLabel.setText(newZipFile.getPath());

}

private void actionAdd() { URL verifiedUrl = verifyUrl(addTextField.getText()); if (verifiedUrl != null) { tableModel.addDownload(new Download(verifiedUrl, saveFileLabel.getText())); addTextField.setText(""); // reset add text field } else { JOptionPane.showMessageDialog(this, "Invalid Download URL", "Error", JOptionPane.ERROR_MESSAGE); } }

private URL verifyUrl(String url) { if (!url.toLowerCase().startsWith("http://")) return null;

URL verifiedUrl = null; try { verifiedUrl = new URL(url); } catch (Exception e) { return null; }

if (verifiedUrl.getFile().length() < 2) return null;

return verifiedUrl; }

private void tableSelectionChanged() { if (selectedDownload != null) selectedDownload.deleteObserver(DownloadManager.this);

if (!clearing && table.getSelectedRow() > -1) { selectedDownload = tableModel.getDownload(table.getSelectedRow()); selectedDownload.addObserver(DownloadManager.this); updateButtons(); } }

private void actionPause() { selectedDownload.pause(); updateButtons(); }

private void actionResume() { selectedDownload.resume(); updateButtons(); }

private void actionCancel() { selectedDownload.cancel(); updateButtons(); }

private void actionClear() { clearing = true; tableModel.clearDownload(table.getSelectedRow()); clearing = false; selectedDownload = null; updateButtons(); }

private void updateButtons() { if (selectedDownload != null) { int status = selectedDownload.getStatus(); switch (status) { case Download.DOWNLOADING: pauseButton.setEnabled(true); resumeButton.setEnabled(false); cancelButton.setEnabled(true); clearButton.setEnabled(false); break; case Download.PAUSED: pauseButton.setEnabled(false); resumeButton.setEnabled(true); cancelButton.setEnabled(true); clearButton.setEnabled(false); break; case Download.ERROR: pauseButton.setEnabled(false); resumeButton.setEnabled(true); cancelButton.setEnabled(false); clearButton.setEnabled(true); break; default: // COMPLETE or CANCELLED pauseButton.setEnabled(false); resumeButton.setEnabled(false); cancelButton.setEnabled(false); clearButton.setEnabled(true); } } else { pauseButton.setEnabled(false); resumeButton.setEnabled(false); cancelButton.setEnabled(false); clearButton.setEnabled(false); } }

public void update(Observable o, Object arg) { // Update buttons if the selected download has changed. if (selectedDownload != null && selectedDownload.equals(o)) updateButtons(); }

// Run the Download Manager. public static void main(String[] args) { DownloadManager manager = new DownloadManager(); manager.setVisible(true); } }

class Download extends Observable implements Runnable { private static final int MAXBUFFERSIZE = 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; // download URL

private String saveDir; // dir to save

private int size; // size of download in bytes

private int downloaded; // number of bytes downloaded

private int status; // current status of download

// Proxy information public static final boolean proxyRequired = true; // Change for your settings public static final String proxyIP = "127.0.0.1"; public static final String proxyPort = "8080"; public static final String proxyUsername = "proxyUser"; public static final String proxyPassword = "proxyPassword";

// Constructor for Download. public Download(URL url, String saveDir) { this.url = url; this.saveDir = saveDir; size = -1; downloaded = 0; status = DOWNLOADING;

// Begin the download. download(); }

// Get this download's URL. public String getUrl() { return url.toString(); }

// Get this download's size. public int getSize() { return size; }

// Get this download's progress. 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(); }

// Get file name portion of URL. public String getFileName(URL url) { String fileName = url.getFile(); return fileName.substring(fileName.lastIndexOf('/') + 1); }

// Download file. public void run() { RandomAccessFile file = null; InputStream stream = null; FileOutputStream out = null;

try {

if (proxyRequired){ // This can be put in a menu, updated via interface System.out.println("Setting proxy"); Properties systemSettings = System.getProperties(); systemSettings.put("http.proxyHost", proxyIP); systemSettings.put("http.proxyPort", proxyPort); System.setProperties(systemSettings); }

// Open connection to URL. HttpURLConnection connection = (HttpURLConnection) url.openConnection();

// Specify what portion of file to download. connection.setRequestProperty("Range", "bytes=" + downloaded + "-");

if (proxyRequired){ String encoded = new String(new sun.misc.BASE64Encoder().encode(new String( proxyUsername + ":" + proxyPassword).getBytes())); connection.setRequestProperty("Proxy-Authorization", "Basic " + encoded); }

System.out.println("Going to make connection"); // Connect to server. connection.connect(); System.out.println("Connected!");

int responseCode = connection.getResponseCode(); System.out.println("Response code from server=" + responseCode);

// Make sure response code is in the 200 range. // 200 - no partial download // 206 - supports resume //if (responseCode / 100 != 2) { if (responseCode == 200 || responseCode == 206) { error(); }

// Check for valid content length. System.out.println("Content length=" + connection.getContentLength()); int contentLength = connection.getContentLength(); if (contentLength < 1) { error(); }

/* * Set the size for this download if it hasn't been already set. */ if (size == -1) { size = contentLength; stateChanged(); }

// Open file and seek to the end of it. file = new RandomAccessFile(getFileName(url), "rw"); file.seek(downloaded);

System.out.println("Get InputStream"); stream = connection.getInputStream(); status = DOWNLOADING; out = new FileOutputStream(saveDir + File.separator + this.getFileName(url)); while (status == DOWNLOADING) { /* * Size buffer according to how much of the file is left to download. */ byte buffer[]; if (size - downloaded > MAXBUFFERSIZE) { buffer = new byte[MAXBUFFERSIZE]; } else { buffer = new byte[size - downloaded]; }

// Read from server into buffer. int read = stream.read(buffer); if (read == -1) break;

// Write buffer to file. //file.write(buffer, 0, read); out.write(buffer, 0, read); downloaded += read; stateChanged(); }

/* * Change status to complete if this point was reached because downloading * has finished. */ if (status == DOWNLOADING) { status = COMPLETE;

stateChanged(); } } catch (Exception e) { System.out.println("Error=" + e); e.printStackTrace(); error(); } finally {

// Close file. if (file != null) { try { // Complete the file out.close(); file.close(); } catch (Exception e) { e.printStackTrace(); } }

// Close connection to server. if (stream != null) { try { stream.close(); } catch (Exception e) { e.printStackTrace(); } } } }

private void stateChanged() { setChanged(); notifyObservers(); } }

class DownloadsTableModel extends AbstractTableModel implements Observer { private static final String[] columnNames = { "URL", "Size", "Progress", "Status" };

private static final Class[] columnClasses = { String.class, String.class, JProgressBar.class, String.class };

private ArrayList<Download> downloadList = new ArrayList<Download>();

public void addDownload(Download download) { download.addObserver(this); downloadList.add(download); fireTableRowsInserted(getRowCount() - 1, getRowCount() - 1); }

public Download getDownload(int row) { return (Download) downloadList.get(row); }

public void clearDownload(int row) { downloadList.remove(row); fireTableRowsDeleted(row, row); }

public int getColumnCount() { return columnNames.length; }

public String getColumnName(int col) { return columnNames[col]; }

public Class getColumnClass(int col) { return columnClasses[col]; }

public int getRowCount() { return downloadList.size(); }

public Object getValueAt(int row, int col) { Download download = downloadList.get(row); switch (col) { case 0: // URL return download.getUrl(); case 1: // Size int size = download.getSize(); return (size == -1) ? "" : Integer.toString(size); case 2: // Progress return new Float(download.getProgress()); case 3: // Status return Download.STATUSES[download.getStatus()]; } return ""; }

public void update(Observable o, Object arg) { int index = downloadList.indexOf(o); fireTableRowsUpdated(index, index); } }

class ProgressRenderer extends JProgressBar implements TableCellRenderer { public ProgressRenderer(int min, int max) { super(min, max); }

public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) { setValue((int) ((Float) value).floatValue()); return this; }

}

To Run

Copy the code above, and paste into a DownloadManager.java file
If you?re behind a proxy, change the proxy settings.
If you?re not behind a proxy, set the proxyRequired = false;
Compile and run

To Download Files

Select the folder you want to save the file
Copy the URL of the file you want to download
Paste to the textbox
Click ?Add to Download?
File will automatically be downloaded
You can click ?Pause? to temporary stop download

Enhancement

Persists directly the file downloaded even if not 100% completed 
File splitting, download a single file with multiple threads

Other useful references

http://www.intel.com/cd/ids/developer/asmo-na/eng/20188.htm?page=1

http://www.intel.com/cd/ids/developer/asmo-na/eng/20187.htm