第一题：简单的URL获取资源下载
import java.net.URL;
import java.net.URLConnection;import java.io.InputStream;
import java.io.FileOutputStream;class DownloadDemo{public static void main(String[] args){String src_url = "http://one.jiangmin.com/jiangmin.zip";try{URL url = new URL(src_url);URLConnection conn = url.openConnection();String type = conn.getContentType();int length = conn.getContentLength();InputStream in = conn.getInputStream();FileOutputStream fos = new FileOutputStream("e:/jiangmin.zip");byte[] buf = new byte[1024];int len = 0;while((len = in.read(buf)) != -1){fos.write(buf);}fos.close();in.close();}catch(Exception e){e.printStackTrace();}}
}第二题：URL多线程下载
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextArea;
import javax.swing.JButton;import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;import java.net.URL;
import java.net.URLConnection;import java.io.InputStream;
import java.io.RandomAccessFile;import java.util.List;
import java.util.ArrayList;class Download{private static final long serialVersionUID = -6944831795769317874L;public static void main(String[] args){new DownloadWindow();}
}class DownloadWindow extends JFrame{private JTextArea url_text;private JTextArea local_text;public DownloadWindow(){ini();}public void ini(){this.setSize(600,400);this.setLocation(600,300);this.setLayout(null);JLabel url_label = new JLabel("URL : ");url_label.setBounds(10,10,100,20);this.add(url_label);url_text = new JTextArea();url_text.setEditable(true);url_text.setBounds(100,10,400,20);this.add(url_text);JLabel local_label = new JLabel("Local : ");local_label.setBounds(10,40,100,20);this.add(local_label);local_text = new JTextArea();local_text.setEditable(true);local_text.setBounds(100,40,400,20);this.add(local_text);JButton down_button = new JButton("Download");down_button.setBounds(200,110,200,50);down_button.addMouseListener(new MouseAdapter(){public void mouseClicked(MouseEvent e){String src_url = url_text.getText();System.out.println(src_url);String local_addr = local_text.getText();new DownloadManager(DownloadWindow.this,src_url,local_addr,5).start();}});this.add(down_button);this.setVisible(true);}
}class DownloadManager{private DownloadWindow window;private String src_url;private String local_addr;private int count;private DownloadInfo info;private List<DownloadInfo> info_list;public DownloadManager(DownloadWindow window,String src_url,String local_addr,int count){this.window = window;this.src_url = src_url;this.local_addr = local_addr;this.count = count;prepareDownload();}public void prepareDownload(){info_list = new ArrayList<DownloadInfo>();try{URL url = new URL(src_url);System.out.println(src_url);int total_length = url.openConnection().getContentLength();RandomAccessFile raf = new RandomAccessFile(local_addr,"rw");raf.setLength(total_length);raf.close();System.out.println(total_length);System.out.println(count);int block = total_length / count;DownloadInfo info = null;for(int i = 0;i < count;i++){info = new DownloadInfo();info.setSrcUrl(src_url);info.setLocalAddr(local_addr);if((count - 1) == i){info.setEndPos(total_length - 1);}else{info.setStartPos((i + 1) * block - 1);}info_list.add(info);}}catch(Exception e){e.printStackTrace();}}public void start(){int i = 0;for(DownloadInfo info : info_list){System.out.println(i);new DownloadThread(window,info).start();i++;}}
}class DownloadThread extends Thread{private DownloadWindow window;private DownloadInfo info;public DownloadThread(DownloadWindow window,DownloadInfo info){this.window = window;this.info = info;}public void run(){try{System.out.println(info.getSrcUrl());URL url = new URL(info.getSrcUrl());URLConnection connect = url.openConnection();connect.setRequestProperty("Range","bytes=" + info.getStartPos() + "-" + info.getEndPos());InputStream in = connect.getInputStream();RandomAccessFile raf = new RandomAccessFile(info.getLocalAddr(),"rw");raf.seek(info.getEndPos());byte[] buf = new byte[1024];int len = 0;while((len = in.read(buf)) != -1){raf.write(buf);}raf.close();}catch(Exception e){e.printStackTrace();}}
}class DownloadInfo{private String src_url;private String local_addr;private int start_pos;private int end_pos;public DownloadInfo(){}public DownloadInfo(String src_url,String local_addr,int start_pos,int end_pos){this.src_url = src_url;this.local_addr = local_addr;this.start_pos = start_pos;this.end_pos = end_pos;}public String getSrcUrl(){return src_url;}public void setSrcUrl(String src_url){this.src_url = src_url;}public String getLocalAddr(){return local_addr;}public void setLocalAddr(String local_addr){this.local_addr = local_addr;}public int getStartPos(){return start_pos;}public void setStartPos(int start_pos){this.start_pos = start_pos;}public int getEndPos(){return end_pos;}public void setEndPos(int end_pos){this.end_pos = end_pos;}
}