code: public static String getIp(String host) {
  		InetAddress address;
  		try {
  			address = InetAddress.getByName(host);
  		}
  		catch (UnknownHostException e) {
  			return null;
  		}
  		return address.getHostAddress();
  	}
docs: 根据域名查询IP，多IP时只返回第一个(查询范围:包括hosts文件、DNS服务器、虚拟DNS).
  
  @param host
  域名
  @return IP