[code=java]        public static void main(String[] args)throws Exception{
                InetAddress LocAdd = null;
                InetAddress remAdd = null;
                LocAdd = InetAddress.getLocalHost();
                remAdd = InetAddress.getByName("http://bbs.itheima.com/");
                System.out.println("本机地址:" + LocAdd);
                System.out.println("外网地址:" + remAdd);
                System.out.println("本机是否可达" + LocAdd.isReachable(5000));
               
                URL url = new URL("http","http://bbs.itheima.com/",80,"/forum-26-1.html");
                InputStream input = url.openStream();        //打开输入流
                Scanner scan = new Scanner(input);        //实例化
                scan.useDelimiter("\n");        //设置分隔符号
                while(scan.hasNext()){
                        System.out.println(scan.next());
                }
        }[/code]运行后 第5、11行报错

Exception in thread "main" java.net.UnknownHostException: http://bbs.itheima.com/
        at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
        at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:849)
        at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1200)
        at java.net.InetAddress.getAllByName0(InetAddress.java:1153)
        at java.net.InetAddress.getAllByName(InetAddress.java:1083)
        at java.net.InetAddress.getAllByName(InetAddress.java:1019)
        at java.net.InetAddress.getByName(InetAddress.java:969)
        at edu.csdn.net.heima.exam.ninth.TcpExamtest.main(TcpExamtest.java:19)

UnknownHostException
未知主机异常，试试看别的网站，或者直接拿到网站的IP和端口

remAdd = InetAddress.getByName("http://bbs.itheima.com/");

URL url = new URL("http","http://bbs.itheima.com/",80,"/forum-26-1.html");
11.               
InputStream input = url.openStream();        //打开输入流


这2段代码都是因为("http://bbs.itheima.com/"); 报错线程发生异常

楼主加上断点 再仔细看看参数 和报错