java怎么获得本机的网关IP地址

import java.io.BufferedReader;import java.io.InputStreamReader;public class ListAllFiles {    public static void main(String[] args) {        try {            Process pro = Runtime.getRuntime()                    .exec("cmd /c ipconfig /all");            InputStreamReader isr = new InputStreamReader(pro.getInputStream());            BufferedReader br = new BufferedReader(isr);            String str = br.readLine();            while(str!=null){                System.out.println(str.trim());                str = br.readLine();            }            br.close();            isr.close();        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}