Java gets a small example of a client Mac address over IP

package com.yswc.dao.sign;
import java.io.BufferedReader;
import java.io.InputStreamReader;

import java.util.regex.Matcher;

import java.util.regex.Pattern;



public class GetMacAddress {

public static String callCmd(String[] cmd) {
  String result = "";
  String line = "";
    try {
        Process proc = Runtime.getRuntime().exec(cmd);
        InputStreamReader is = new InputStreamReader(proc.getInputStream());
        BufferedReader br = new BufferedReader (is);
        while ((line = br.readLine ()) != null) {
             result += line;
        }
   }catch(Exception e) {
        e.printStackTrace();
   }
      return result;
} 


public static String callCmd(String[] cmd,String[] another) {
   String result = "";
   String line = "";
   try {
      Runtime rt = Runtime.getRuntime();
      Process proc = rt.exec(cmd);
      proc.waitFor(); //Having executed the first command, we are ready to execute the second
      proc = rt.exec(another);
      InputStreamReader is = new InputStreamReader(proc.getInputStream());
      BufferedReader br = new BufferedReader (is);
      while ((line = br.readLine ()) != null) {
         result += line;
      }
   }catch(Exception e) {
        e.printStackTrace();
   }
      return result;
}



public static String filterMacAddress(final String ip, final String sourceString,final String macSeparator) {
   String result = "";
   String regExp = "((([0-9,A-F,a-f]{1,2}" + macSeparator + "){1,5})[0-9,A-F,a-f]{1,2})";
   Pattern pattern = Pattern.compile(regExp);
   Matcher matcher = pattern.matcher(sourceString);
   while(matcher.find()){
     result = matcher.group(1);
     if(sourceString.indexOf(ip) <= sourceString.lastIndexOf(matcher.group(1))) {
        break; //If there are multiple ips, only the Mac corresponding to this IP is matched.
     }
   }
    return result;
}



public static String getMacInWindows(final String ip){
   String result = "";
   String[] cmd = {"cmd","/c","ping " + ip};
   String[] another = {"cmd","/c","arp -a"};
   String cmdResult = callCmd(cmd,another);
   result = filterMacAddress(ip,cmdResult,"-");
   return result;
} 
 
 public static String getMacInLinux(final String ip){  
     String result = "";  
     String[] cmd = {"/bin/sh","-c","ping " +  ip + " -c 2 && arp -a" };  
     String cmdResult = callCmd(cmd);  
     result = filterMacAddress(ip,cmdResult,":");  
     return result;  
 }  

 
 public static String getMacAddress(String ip){
     String macAddress = "";
     macAddress = getMacInWindows(ip).trim();
     if(macAddress==null||"".equals(macAddress)){
         macAddress = getMacInLinux(ip).trim();
     }
     return macAddress;
 }
 public static void main(String[] args) {
 String mac=getMacAddress("192.168.1.102");
 System.out.println("mac:"+mac);
}

}