类继承的问题。。。。 看不懂源码,求教。
import java.io.*;
import java.net.*;
public class GetHttp{
public static void main(String[] args) throws Exception{
URL targetUrl = null;
HttpURLConnection httpUrl = null;
BufferedInputStream bis = null;
FileOutputStream fos = null;
byte[] buf = new byte[1024];
int size = 0;
System.out.println(0 + args[0]);
System.out.println(1 + args[1]);
//System.out.println(args[2]);
if(args.length != 2){
System.out.println("usage: GetHttp targeturl targetfile");
return;
}
targetUrl=new URL(args[0]);
httpUrl = (HttpURLConnection) targetUrl.openConnection();
//httpUrl = new HttpURLConnection(new URL(args[0]));
httpUrl.connect(); //***这一行***
bis =new BufferedInputStream(httpUrl.getInputStream());
fos = new FileOutputStream(args[1]);
System.out.println("正从[" + args[0] + "]下载文件,并保存为[" + args[1] + "]");
while( (size = bis.read(buf)) != -1){
fos.write(buf,0,size);
}
fos.close();
bis.close();
httpUrl.disconnect();
}
}
//:~
请问其中的httpUrl.connect();这行里的connect是使用那个类的函数,因为httpUrlConnect这个类的定义如下:
public abstract class HttpURLConnectionextends URLConnection
然后URLConnection也是抽像类,它的connect定义也是抽像的,那到底这个函数是在那里实现的呢?
abstract void connect()