public static void main(String[] args) throws IOException
{
String ip = "192.168.8.";
for (int i = 1 ; i < 256; i++)
{
String host = ip+i;
InetAddress ia = InetAddress.getByName(host);
boolean bool = ia.isReachable(1500);
if (bool)
{
System.out.println("主机: "+host+" 可用");
}

}



}

如上方式实现，速度过慢。
如果用多线程，导致结果错误。
public static void main(String[] args) throws IOException
{
String ip = "192.168.8.";
// for (int i = 1 ; i < 256; i++)
// {
// String host = ip+i;
// InetAddress ia = InetAddress.getByName(host);
// boolean bool = ia.isReachable(1500);
// if (bool)
// {
// System.out.println("主机: "+host+" 可用");
// }
//
// new Thread1(host).start();
// }

for (int i = 1 ; i < 15; i++)
{
String host = ip+i;
new Thread1(host).start();
}


}

static class Thread1 extends Thread
{
String ip = null;

public Thread1(String ip)
{
super();
this.ip = ip;
}

@Override
public void run()
{
super.run();


try
{
InetAddress ia = InetAddress.getByName(ip);
boolean bool = ia.isReachable(1500);
if (bool)
{
System.out.println("主机: "+ip+" 可用");
}
}
catch (UnknownHostException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}



}


}


求优化
要求不能 调用系统的ping来实现