public static void main(String[] args) throws Exception {
InetAddress ia = InetAddress.getLocalHost();
System.out.println(getMACAddress(ia));
}

private static String getMACAddress(InetAddress ia) throws Exception {
// 获得网络接口对象（即网卡），并得到mac地址，mac地址存在于一个byte数组中。
byte[] mac = NetworkInterface.getByInetAddress(ia).getHardwareAddress();

// 下面代码是把mac地址拼装成String
StringBuffer sb = new StringBuffer();

for (int i = 0; i < mac.length; i++) {
if (i != 0) {
sb.append("-");
}
// mac[i] & 0xFF 是为了把byte转化为正整数
String s = Integer.toHexString(mac[i] & 0xFF);
sb.append(s.length() == 1 ? 0 + s : s);
}

// 把字符串所有小写字母改为大写成为正规的mac地址并返回
return sb.toString().toUpperCase();
}

public static void main(String[] args) throws Exception {
getMac("192.168.1.186");
}

public static String getMac(String ip){
String str = null;
String mac = null;
try{
Process p = Runtime.getRuntime().exec("nbtstat -A " + ip); 
InputStreamReader ir = new InputStreamReader(p.getInputStream(),"gbk"); 
LineNumberReader input = new LineNumberReader(ir); 
for (; true;) { 
str = input.readLine(); 
if (str != null) {
if (str.indexOf("MAC 地址") > 1) {
mac = str.substring(str.indexOf("MAC 地址") + 9);
break; 
}
}
}
System.out.println(mac);
}catch(IOException e){
e.printStackTrace();
}
return mac;
}