怎么取公网的IP地址？

写了个程序，就是只能取出局域网的IP，郁闷呀，那位大哥帮帮忙？小弟先谢过了！！

import java.net.InetAddress;

public class IP {
public static void main (String[] args)throws Exception {
InetAddress address=InetAddress.getLocalHost();
String hostName=address.getHostName();
System.out.println("HostName:"+hostName);
InetAddress addresses[]=InetAddress.getAllByName(hostName);
for(int i=0;i<addresses.length;i++){
System.out.println("hostAddress"+i+":"+addresses[i].getHostAddress());
}
}
}