Java网络编程--简易下载器实现

package study;

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

public class Main {
static String source = "http://down.daomuxiaoshuo.com/down/201304/gcd.txt";
String fileName = null;
URL url = null;
InputStream in = null;
static File file = null;
DataOutputStream dos = null;
URLConnection con = null;

// 连接
public void connection() {
try {
url = new URL(source);
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
con = url.openConnection();
} catch (IOException e) {
e.printStackTrace();
}
}

// 创建本地文件
public void createFile() {
file = new File(fileName);
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
}
//将从网络获取的文件的InputStream并写入到本地
private void writeResult()
{
FileOutputStream fos = null;
try
{
fos = new FileOutputStream(file,true);
}
catch(FileNotFoundException e)
{
e.printStackTrace();
}
BufferedOutputStream bos = new BufferedOutputStream(fos);
dos = new DataOutputStream(bos);
try{
in = con.getInputStream();
}catch(IOException e)
{
e.printStackTrace();
}
BufferedInputStream bis = new BufferedInputStream(in);

DataInputStream dis = new DataInputStream(bis);
try
{
while(true)
{
dos.write(dis.readByte());
}
}
catch(EOFException e)
{
System.out.println("DownLoad!");
}
catch(IOException e)
{
e.printStackTrace();
}
try
{
dos.close();
bis.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
public void setFileName(String sourceUrl)
{
fileName = sourceUrl.substring(sourceUrl.lastIndexOf("/")+1,sourceUrl.length()).trim();
}
public static void main(String[] args) {
Main main = new Main();
main.setFileName(source);
main.connection();
main.createFile();
main.writeResult();
}

}