Java实现多线程下载源代码

package MultiThreadDownLoad; import java.awt.event.KeyEvent; import java.io.File; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLDecoder; import java.util.Observable; import java.util.Observer; import javax.swing.JFileChooser; import javax.swing.JOptionPane; public class DownLoad extends javax.swing.JFrame implements Observer { public DownLoad() { initComponents(); jButtonOpenFolder.setEnabled(false); } private String fileName;//文件名 private String houZhui;//文件后缀 private String path;//自定义路径(目录) private String savePath;//详细路径及文件 private long startTime, endTime;//定义初始、结束时间变量 public static int finishedThread = 0;//已完成的线程数 private int threadNum;//线程数量 private String sourcePath;//网址的字符串形式(源地址) private long totalSize;//所下载文件的大小 private void startDownLowd(){ if(jTextFieldURL.getText().equals("")){ JOptionPane.showMessageDialog(this, "请输入文件下载地址！"); }else{ downloadFile(); } } private void downloadFile() { jButtonDownLoad.setEnabled(false); try { URL u = new URL(URLDecoder.decode(jTextFieldURL.getText(), "gbk"));//解码 HttpURLConnection huc = (HttpURLConnection) u.openConnection();//生成一个HttpURLConnection对象 //先测试该站点是否支持断点下载 huc.setRequestMethod("HEAD"); totalSize = huc.getContentLength(); String s = huc.getHeaderField("Accept-Ranges"); if (s == null || !s.equals("bytes")) { JOptionPane.showMessageDialog(this, "请求的文件不支持断点下载！"); jButtonDownLoad.setEnabled(true); return; } //如果支持断点就继续进行！ sourcePath = u.toString();//把该URL转成字符串的形式 String pathName = u.getFile(); houZhui = pathName.substring(pathName.lastIndexOf('.'));//获取源文件的文件名 if(jTextFieldMuLu.getText().equals("")){ String filename=pathName.substring(pathName.lastIndexOf('/') + 1); File file = new File(""); path = file.getAbsolutePath(); jTextFieldMuLu.setText(path); jTextFieldRename.setText(filename); savePath = path + File.separator + filename; } else { fileName = jTextFieldRename.getText(); path = jTextFieldMuLu.getText(); savePath = path + File.separator + fileName + houZhui; //所下载文件的所在路径 jTextFieldRename.setText(fileName + houZhui); } //具体的多线程下载分配 threadNum = this.jComboBoxThreadNumbers.getSelectedIndex() + 1;//设置线程数 int averageThreadSize = (int) (totalSize / threadNum);//每个线程需要下载文件的字节数 startTime = System.currentTimeMillis(); //启动所有线程 for (int i = 0; i < threadNum; i++) { if (i == threadNum - 1) { MultiThreadDownLoadFiles f = new MultiThreadDownLoadFiles(savePath, sourcePath, (long) (i * averageThreadSize), (long) (totalSize - 1)); //添加对f的观察者 f.addObserver(this); new Thread(f).start(); } else { MultiThreadDownLoadFiles f = new MultiThreadDownLoadFiles(savePath, sourcePath, (long) (i * averageThreadSize), (long) ((i + 1) * averageThreadSize - 1)); f.addObserver(this); new Thread(f).start(); } } } catch (Exception ie) { } } public void update(Observable arg0, Object arg1) { if (DownLoad.finishedThread == threadNum) { endTime = System.currentTimeMillis(); int returnValue = JOptionPane.showConfirmDialog(this, "下载完毕！总耗时" + (endTime - startTime) / 1000 + "秒。\n是否打开文件所在文件夹？", "请注意了......", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE); if (returnValue == JOptionPane.YES_OPTION) { try { Runtime.getRuntime().exec("rundll32 SHELL32.DLL,ShellExec_RunDLL " + path); //打开文件所在的文件夹 } catch (Exception e) { } } jButtonDownLoad.setEnabled(true); jButtonOpenFolder.setEnabled(true); DownLoad.finishedThread = 0;//完成后重新置为0 } } private void scan(){ JFileChooser foder = new JFileChooser(); foder.setCurrentDirectory(new File(".")); foder.setDialogType(JFileChooser.DIRECTORIES_ONLY + JFileChooser.SAVE_DIALOG); foder.setDialogTitle("请你选择所要保存文件的路径"); if (foder.showSaveDialog(this) != JFileChooser.APPROVE_OPTION) { return; } path = foder.getCurrentDirectory().getAbsolutePath(); jTextFieldMuLu.setText(path); fileName = foder.getName(foder.getSelectedFile()); jTextFieldRename.setText(fileName); } // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents private void initComponents() { jPanel1 = new javax.swing.JPanel(); jLabel1 = new javax.swing.JLabel(); jTextFieldURL = new javax.swing.JTextField(); jSeparator1 = new javax.swing.JSeparator(); jLabel2 = new javax.swing.JLabel(); jTextFieldMuLu = new javax.swing.JTextField(); jLabel4 = new javax.swing.JLabel(); jTextFieldRename = new javax.swing.JTextField(); jSeparator2 = new javax.swing.JSeparator(); jLabelThreadNumber = new javax.swing.JLabel(); jComboBoxThreadNumbers = new javax.swing.JComboBox(); jButtonScan = new javax.swing.JButton(); jLabel5 = new javax.swing.JLabel(); jButtonDownLoad = new javax.swing.JButton(); jButtonExit = new javax.swing.JButton(); jButtonOpenFolder = new javax.swing.JButton(); setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE); setTitle("新的下载"); setResizable(false); jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder("")); jLabel1.setFont(new java.awt.Font("宋体", 0, 14)); jLabel1.setText("URL："); jTextFieldURL.addKeyListener(new java.awt.event.KeyAdapter() { public void keyPressed(java.awt.event.KeyEvent evt) { jTextFieldURLKeyPressed(evt); } }); jLabel2.setFont(new java.awt.Font("宋体", 0, 14)); jLabel2.setText("存储目录："); jLabel4.setFont(new java.awt.Font("宋体", 0, 14)); jLabel4.setText("另存名称："); jLabelThreadNumber.setFont(new java.awt.Font("宋体", 0, 14)); jLabelThreadNumber.setText("请选择线程数："); jComboBoxThreadNumbers.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "1个线程", "2个线程", "3个线程", "4个线程", "5个线程", "6个线程", "7个线程", "8个线程" })); jButtonScan.setText("浏览..."); jButtonScan.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { jButtonScanActionPerformed(evt); } }); javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1); jPanel1.setLayout(jPanel1Layout); jPanel1Layout.setHorizontalGroup( jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Align